[1/2] PCI: dwc: Add support to disable GEN3 equalization
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Message ID 1568118302-10505-1-git-send-email-pankaj.dubey@samsung.com
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  • [1/2] PCI: dwc: Add support to disable GEN3 equalization
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Commit Message

Pankaj Dubey Sept. 10, 2019, 12:25 p.m. UTC
From: Anvesh Salveru <anvesh.s@samsung.com>

In some platforms, PCIe PHY may have issues which will prevent linkup
to happen in GEN3 or high speed. In case equalization fails, link will
fallback to GEN1.

Designware controller has support for disabling GEN3 equalization if
required. This patch enables the designware driver to disable the PCIe
GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.

Platform drivers can disable equalization by setting the dwc_pci_quirk
flag DWC_EQUALIZATION_DISABLE.

Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
---
 drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
 drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
 2 files changed, 14 insertions(+)

Comments

Andrew Murray Sept. 10, 2019, 1:58 p.m. UTC | #1
On Tue, Sep 10, 2019 at 05:55:01PM +0530, Pankaj Dubey wrote:
> From: Anvesh Salveru <anvesh.s@samsung.com>
> 
> In some platforms, PCIe PHY may have issues which will prevent linkup
> to happen in GEN3 or high speed. In case equalization fails, link will
> fallback to GEN1.

When you refer to "high speed", do you mean "higher speeds" as in GEN3,
GEN4, etc?

> 
> Designware controller has support for disabling GEN3 equalization if
> required. This patch enables the designware driver to disable the PCIe
> GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.

Thus limiting to GEN2 speeds max, right?

Is the purpose of PORT_LOGIC_GEN3_EQ_DISABLE to disable GEN3 and above
even though we advertise GEN3 and above speeds? I.e. the IP advertises
GEN3 but the phy can't handle it, we can't change what the IP advertises
and so we disable equalization to limit to GEN2?

I notice many of the other dwc drivers (dra7xx, keystone, tegra194, imx6)
seem to use the device tree to specify a max-link-speed and then impose
that limit by changing the value in PCI_EXP_LNKCAP. Is your
PORT_LOGIC_GEN3_EQ_DISABLE approach and alternative to the PCI_EXP_LNKCAP
approach, or does your approach add something else?

> 
> Platform drivers can disable equalization by setting the dwc_pci_quirk
> flag DWC_EQUALIZATION_DISABLE.
> 
> Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
>  drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 7d25102..bf82091 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  		break;
>  	}
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> +
> +	val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +
> +	if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> +
> +	dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);

The problem here is that even when DWC_EQUALIZATION_DISABLE is not set
the driver will read and write PCIE_PORT_GEN3_RELATED when it is not
needed. How about something like:

> +
> +	if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) {
> +	        val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> +	        dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> +     }

>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index ffed084..a1453c5 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -29,6 +29,9 @@
>  #define LINK_WAIT_MAX_IATU_RETRIES	5
>  #define LINK_WAIT_IATU			9
>  
> +/* Parameters for PCIe Quirks */
> +#define DWC_EQUALIZATION_DISABLE	0x1

How about using BIT(1) instead? Thus implying that you can combine
quirks.

Thanks,

Andrew Murray

> +
>  /* Synopsys-specific PCIe configuration registers */
>  #define PCIE_PORT_LINK_CONTROL		0x710
>  #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
> @@ -60,6 +63,9 @@
>  #define PCIE_MSI_INTR0_MASK		0x82C
>  #define PCIE_MSI_INTR0_STATUS		0x830
>  
> +#define PCIE_PORT_GEN3_RELATED		0x890
> +#define PORT_LOGIC_GEN3_EQ_DISABLE	BIT(16)
> +
>  #define PCIE_ATU_VIEWPORT		0x900
>  #define PCIE_ATU_REGION_INBOUND		BIT(31)
>  #define PCIE_ATU_REGION_OUTBOUND	0
> @@ -244,6 +250,7 @@ struct dw_pcie {
>  	struct dw_pcie_ep	ep;
>  	const struct dw_pcie_ops *ops;
>  	unsigned int		version;
> +	unsigned int		dwc_pci_quirk;
>  };
>  
>  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> -- 
> 2.7.4
>
Pankaj Dubey Sept. 10, 2019, 4:16 p.m. UTC | #2
On Tue, 10 Sep 2019 at 19:56, Andrew Murray <andrew.murray@arm.com> wrote:
>
> On Tue, Sep 10, 2019 at 05:55:01PM +0530, Pankaj Dubey wrote:
> > From: Anvesh Salveru <anvesh.s@samsung.com>
> >
> > In some platforms, PCIe PHY may have issues which will prevent linkup
> > to happen in GEN3 or high speed. In case equalization fails, link will
> > fallback to GEN1.
>
> When you refer to "high speed", do you mean "higher speeds" as in GEN3,
> GEN4, etc?
>

Yes. Will reword the commit message as "higher speeds"

> >
> > Designware controller has support for disabling GEN3 equalization if
> > required. This patch enables the designware driver to disable the PCIe
> > GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.
>
> Thus limiting to GEN2 speeds max, right?
>
> Is the purpose of PORT_LOGIC_GEN3_EQ_DISABLE to disable GEN3 and above
> even though we advertise GEN3 and above speeds? I.e. the IP advertises
> GEN3 but the phy can't handle it, we can't change what the IP advertises
> and so we disable equalization to limit to GEN2?
>
> I notice many of the other dwc drivers (dra7xx, keystone, tegra194, imx6)
> seem to use the device tree to specify a max-link-speed and then impose
> that limit by changing the value in PCI_EXP_LNKCAP. Is your
> PORT_LOGIC_GEN3_EQ_DISABLE approach and alternative to the PCI_EXP_LNKCAP
> approach, or does your approach add something else?
>

No, max speed will be still as per advertised by link or it will be
equal to the limited speed as per DT property if any.
This register will prohibit to perform all phases of equalization and
thus allowing link to happen in maximum supported/advertised speed.

This is not to limit max link speed, this register helps link to
happen in higher speeds (GEN3/4) without going through equalization
phases. It is intended to use only if at all link fails to latch up in
GEN3/4 due to failure in equalization phases.

> >
> > Platform drivers can disable equalization by setting the dwc_pci_quirk
> > flag DWC_EQUALIZATION_DISABLE.
> >
> > Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
> >  drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
> >  2 files changed, 14 insertions(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> > index 7d25102..bf82091 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
> >               break;
> >       }
> >       dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> > +
> > +     val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > +
> > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > +
> > +     dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
>
> The problem here is that even when DWC_EQUALIZATION_DISABLE is not set
> the driver will read and write PCIE_PORT_GEN3_RELATED when it is not
> needed. How about something like:
>
> > +
> > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) {
> > +             val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > +             dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > +     }
>

Yes, before posting we taught about it, but then next patchset is
adding one more quirk and in that case we need to repeat read and
write under each if condition. I hope that repetition should be fine.

> >  }
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> > index ffed084..a1453c5 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > @@ -29,6 +29,9 @@
> >  #define LINK_WAIT_MAX_IATU_RETRIES   5
> >  #define LINK_WAIT_IATU                       9
> >
> > +/* Parameters for PCIe Quirks */
> > +#define DWC_EQUALIZATION_DISABLE     0x1
>
> How about using BIT(1) instead? Thus implying that you can combine
> quirks.
>

Agreed.

> Thanks,
>
> Andrew Murray
>
> > +
> >  /* Synopsys-specific PCIe configuration registers */
> >  #define PCIE_PORT_LINK_CONTROL               0x710
> >  #define PORT_LINK_MODE_MASK          GENMASK(21, 16)
> > @@ -60,6 +63,9 @@
> >  #define PCIE_MSI_INTR0_MASK          0x82C
> >  #define PCIE_MSI_INTR0_STATUS                0x830
> >
> > +#define PCIE_PORT_GEN3_RELATED               0x890
> > +#define PORT_LOGIC_GEN3_EQ_DISABLE   BIT(16)
> > +
> >  #define PCIE_ATU_VIEWPORT            0x900
> >  #define PCIE_ATU_REGION_INBOUND              BIT(31)
> >  #define PCIE_ATU_REGION_OUTBOUND     0
> > @@ -244,6 +250,7 @@ struct dw_pcie {
> >       struct dw_pcie_ep       ep;
> >       const struct dw_pcie_ops *ops;
> >       unsigned int            version;
> > +     unsigned int            dwc_pci_quirk;
> >  };
> >
> >  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> > --
> > 2.7.4
> >
Andrew Murray Sept. 11, 2019, 9:23 a.m. UTC | #3
On Tue, Sep 10, 2019 at 09:46:28PM +0530, Pankaj Dubey wrote:
> On Tue, 10 Sep 2019 at 19:56, Andrew Murray <andrew.murray@arm.com> wrote:
> >
> > On Tue, Sep 10, 2019 at 05:55:01PM +0530, Pankaj Dubey wrote:
> > > From: Anvesh Salveru <anvesh.s@samsung.com>
> > >
> > > In some platforms, PCIe PHY may have issues which will prevent linkup
> > > to happen in GEN3 or high speed. In case equalization fails, link will
> > > fallback to GEN1.
> >
> > When you refer to "high speed", do you mean "higher speeds" as in GEN3,
> > GEN4, etc?
> >
> 
> Yes. Will reword the commit message as "higher speeds"
> 
> > >
> > > Designware controller has support for disabling GEN3 equalization if
> > > required. This patch enables the designware driver to disable the PCIe
> > > GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.
> >
> > Thus limiting to GEN2 speeds max, right?
> >
> > Is the purpose of PORT_LOGIC_GEN3_EQ_DISABLE to disable GEN3 and above
> > even though we advertise GEN3 and above speeds? I.e. the IP advertises
> > GEN3 but the phy can't handle it, we can't change what the IP advertises
> > and so we disable equalization to limit to GEN2?
> >
> > I notice many of the other dwc drivers (dra7xx, keystone, tegra194, imx6)
> > seem to use the device tree to specify a max-link-speed and then impose
> > that limit by changing the value in PCI_EXP_LNKCAP. Is your
> > PORT_LOGIC_GEN3_EQ_DISABLE approach and alternative to the PCI_EXP_LNKCAP
> > approach, or does your approach add something else?
> >
> 
> No, max speed will be still as per advertised by link or it will be
> equal to the limited speed as per DT property if any.
> This register will prohibit to perform all phases of equalization and
> thus allowing link to happen in maximum supported/advertised speed.
> 
> This is not to limit max link speed, this register helps link to
> happen in higher speeds (GEN3/4) without going through equalization
> phases. It is intended to use only if at all link fails to latch up in
> GEN3/4 due to failure in equalization phases.

I thought that for GEN3 and beyond equalization was *required* - with only
phases 2 and 3 being optional. Therefore I'm suprised to see that if
equalization does fail we continue to train the link anyway. Have I
understood this correctly?

Also are there any plans to provide patches to use this quirk on any
drivers?

> 
> > >
> > > Platform drivers can disable equalization by setting the dwc_pci_quirk
> > > flag DWC_EQUALIZATION_DISABLE.
> > >
> > > Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> > > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
> > >  drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
> > >  2 files changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> > > index 7d25102..bf82091 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > > @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
> > >               break;
> > >       }
> > >       dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> > > +
> > > +     val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > +
> > > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> > > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > +
> > > +     dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> >
> > The problem here is that even when DWC_EQUALIZATION_DISABLE is not set
> > the driver will read and write PCIE_PORT_GEN3_RELATED when it is not
> > needed. How about something like:
> >
> > > +
> > > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) {
> > > +             val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > +             dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > > +     }
> >
> 
> Yes, before posting we taught about it, but then next patchset is
> adding one more quirk and in that case we need to repeat read and
> write under each if condition. I hope that repetition should be fine.

I understand. I think the repetition is prefered over needlessly reading and
writing registers.

Given these quirks are so similar, I wouldn't have a problem with them being
in the same patch.

Thanks,

Andrew Murray

> 
> > >  }
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> > > index ffed084..a1453c5 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > > @@ -29,6 +29,9 @@
> > >  #define LINK_WAIT_MAX_IATU_RETRIES   5
> > >  #define LINK_WAIT_IATU                       9
> > >
> > > +/* Parameters for PCIe Quirks */
> > > +#define DWC_EQUALIZATION_DISABLE     0x1
> >
> > How about using BIT(1) instead? Thus implying that you can combine
> > quirks.
> >
> 
> Agreed.
> 
> > Thanks,
> >
> > Andrew Murray
> >
> > > +
> > >  /* Synopsys-specific PCIe configuration registers */
> > >  #define PCIE_PORT_LINK_CONTROL               0x710
> > >  #define PORT_LINK_MODE_MASK          GENMASK(21, 16)
> > > @@ -60,6 +63,9 @@
> > >  #define PCIE_MSI_INTR0_MASK          0x82C
> > >  #define PCIE_MSI_INTR0_STATUS                0x830
> > >
> > > +#define PCIE_PORT_GEN3_RELATED               0x890
> > > +#define PORT_LOGIC_GEN3_EQ_DISABLE   BIT(16)
> > > +
> > >  #define PCIE_ATU_VIEWPORT            0x900
> > >  #define PCIE_ATU_REGION_INBOUND              BIT(31)
> > >  #define PCIE_ATU_REGION_OUTBOUND     0
> > > @@ -244,6 +250,7 @@ struct dw_pcie {
> > >       struct dw_pcie_ep       ep;
> > >       const struct dw_pcie_ops *ops;
> > >       unsigned int            version;
> > > +     unsigned int            dwc_pci_quirk;
> > >  };
> > >
> > >  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> > > --
> > > 2.7.4
> > >
Pankaj Dubey Sept. 12, 2019, 11:39 a.m. UTC | #4
> From: Andrew Murray <andrew.murray@arm.com>
> 
> On Tue, Sep 10, 2019 at 09:46:28PM +0530, Pankaj Dubey wrote:
> > On Tue, 10 Sep 2019 at 19:56, Andrew Murray <andrew.murray@arm.com>
> wrote:
> > >
> > > On Tue, Sep 10, 2019 at 05:55:01PM +0530, Pankaj Dubey wrote:
> > > > From: Anvesh Salveru <anvesh.s@samsung.com>
> > > >
> > > > In some platforms, PCIe PHY may have issues which will prevent
> > > > linkup to happen in GEN3 or high speed. In case equalization
> > > > fails, link will fallback to GEN1.
> > >
> > > When you refer to "high speed", do you mean "higher speeds" as in
> > > GEN3, GEN4, etc?
> > >
> >
> > Yes. Will reword the commit message as "higher speeds"
> >
> > > >
> > > > Designware controller has support for disabling GEN3 equalization
> > > > if required. This patch enables the designware driver to disable
> > > > the PCIe
> > > > GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.
> > >
> > > Thus limiting to GEN2 speeds max, right?
> > >
> > > Is the purpose of PORT_LOGIC_GEN3_EQ_DISABLE to disable GEN3 and
> > > above even though we advertise GEN3 and above speeds? I.e. the IP
> > > advertises
> > > GEN3 but the phy can't handle it, we can't change what the IP
> > > advertises and so we disable equalization to limit to GEN2?
> > >
> > > I notice many of the other dwc drivers (dra7xx, keystone, tegra194,
> > > imx6) seem to use the device tree to specify a max-link-speed and
> > > then impose that limit by changing the value in PCI_EXP_LNKCAP. Is
> > > your PORT_LOGIC_GEN3_EQ_DISABLE approach and alternative to the
> > > PCI_EXP_LNKCAP approach, or does your approach add something else?
> > >
> >
> > No, max speed will be still as per advertised by link or it will be
> > equal to the limited speed as per DT property if any.
> > This register will prohibit to perform all phases of equalization and
> > thus allowing link to happen in maximum supported/advertised speed.
> >
> > This is not to limit max link speed, this register helps link to
> > happen in higher speeds (GEN3/4) without going through equalization
> > phases. It is intended to use only if at all link fails to latch up in
> > GEN3/4 due to failure in equalization phases.
> 
> I thought that for GEN3 and beyond equalization was *required* - with only
> phases 2 and 3 being optional. Therefore I'm suprised to see that if
equalization
> does fail we continue to train the link anyway. Have I understood this
correctly?
> 

AFAIK, equalization is not mandatory for GEN3 and higher speed. I mean in
case there is some H/W issue we can still go ahead and disable complete
equalization.

> Also are there any plans to provide patches to use this quirk on any
drivers?
> 

Yes, we have plans and soon the user driver of this feature will land for
review. But I believe this should not be blocker to consider this patch, as
it is a feature provided in Designware H/W and so we can add S/W support for
the same.

> >
> > > >
> > > > Platform drivers can disable equalization by setting the
> > > > dwc_pci_quirk flag DWC_EQUALIZATION_DISABLE.
> > > >
> > > > Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> > > > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > > > ---
> > > >  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
> > > > drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
> > > >  2 files changed, 14 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > > > b/drivers/pci/controller/dwc/pcie-designware.c
> > > > index 7d25102..bf82091 100644
> > > > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > > > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > > > @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
> > > >               break;
> > > >       }
> > > >       dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> > > > +
> > > > +     val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > > +
> > > > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> > > > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > > +
> > > > +     dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > >
> > > The problem here is that even when DWC_EQUALIZATION_DISABLE is not
> > > set the driver will read and write PCIE_PORT_GEN3_RELATED when it is
> > > not needed. How about something like:
> > >
> > > > +
> > > > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) {
> > > > +             val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > > +             dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > > > +     }
> > >
> >
> > Yes, before posting we taught about it, but then next patchset is
> > adding one more quirk and in that case we need to repeat read and
> > write under each if condition. I hope that repetition should be fine.
> 
> I understand. I think the repetition is prefered over needlessly reading
and
> writing registers.
> 

OK, will handle this in v2.

> Given these quirks are so similar, I wouldn't have a problem with them
being in
> the same patch.
> 

I still prefer to keep these in two separate patches, unless until it is
something mandatory.

> Thanks,
> 
> Andrew Murray
> 
> >
> > > >  }
> > > > diff --git a/drivers/pci/controller/dwc/pcie-designware.h
> > > > b/drivers/pci/controller/dwc/pcie-designware.h
> > > > index ffed084..a1453c5 100644
> > > > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > > > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > > > @@ -29,6 +29,9 @@
> > > >  #define LINK_WAIT_MAX_IATU_RETRIES   5
> > > >  #define LINK_WAIT_IATU                       9
> > > >
> > > > +/* Parameters for PCIe Quirks */
> > > > +#define DWC_EQUALIZATION_DISABLE     0x1
> > >
> > > How about using BIT(1) instead? Thus implying that you can combine
> > > quirks.
> > >
> >
> > Agreed.
> >
> > > Thanks,
> > >
> > > Andrew Murray
> > >
> > > > +
> > > >  /* Synopsys-specific PCIe configuration registers */
> > > >  #define PCIE_PORT_LINK_CONTROL               0x710
> > > >  #define PORT_LINK_MODE_MASK          GENMASK(21, 16)
> > > > @@ -60,6 +63,9 @@
> > > >  #define PCIE_MSI_INTR0_MASK          0x82C
> > > >  #define PCIE_MSI_INTR0_STATUS                0x830
> > > >
> > > > +#define PCIE_PORT_GEN3_RELATED               0x890
> > > > +#define PORT_LOGIC_GEN3_EQ_DISABLE   BIT(16)
> > > > +
> > > >  #define PCIE_ATU_VIEWPORT            0x900
> > > >  #define PCIE_ATU_REGION_INBOUND              BIT(31)
> > > >  #define PCIE_ATU_REGION_OUTBOUND     0
> > > > @@ -244,6 +250,7 @@ struct dw_pcie {
> > > >       struct dw_pcie_ep       ep;
> > > >       const struct dw_pcie_ops *ops;
> > > >       unsigned int            version;
> > > > +     unsigned int            dwc_pci_quirk;
> > > >  };
> > > >
> > > >  #define to_dw_pcie_from_pp(port) container_of((port), struct
> > > > dw_pcie, pp)
> > > > --
> > > > 2.7.4
> > > >
Andrew Murray Sept. 12, 2019, 12:42 p.m. UTC | #5
On Thu, Sep 12, 2019 at 05:09:41PM +0530, Pankaj Dubey wrote:
> 
> 
> > From: Andrew Murray <andrew.murray@arm.com>
> > 
> > On Tue, Sep 10, 2019 at 09:46:28PM +0530, Pankaj Dubey wrote:
> > > On Tue, 10 Sep 2019 at 19:56, Andrew Murray <andrew.murray@arm.com>
> > wrote:
> > > >
> > > > On Tue, Sep 10, 2019 at 05:55:01PM +0530, Pankaj Dubey wrote:
> > > > > From: Anvesh Salveru <anvesh.s@samsung.com>
> > > > >
> > > > > In some platforms, PCIe PHY may have issues which will prevent
> > > > > linkup to happen in GEN3 or high speed. In case equalization
> > > > > fails, link will fallback to GEN1.
> > > >
> > > > When you refer to "high speed", do you mean "higher speeds" as in
> > > > GEN3, GEN4, etc?
> > > >
> > >
> > > Yes. Will reword the commit message as "higher speeds"
> > >
> > > > >
> > > > > Designware controller has support for disabling GEN3 equalization
> > > > > if required. This patch enables the designware driver to disable
> > > > > the PCIe
> > > > > GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.
> > > >
> > > > Thus limiting to GEN2 speeds max, right?
> > > >
> > > > Is the purpose of PORT_LOGIC_GEN3_EQ_DISABLE to disable GEN3 and
> > > > above even though we advertise GEN3 and above speeds? I.e. the IP
> > > > advertises
> > > > GEN3 but the phy can't handle it, we can't change what the IP
> > > > advertises and so we disable equalization to limit to GEN2?
> > > >
> > > > I notice many of the other dwc drivers (dra7xx, keystone, tegra194,
> > > > imx6) seem to use the device tree to specify a max-link-speed and
> > > > then impose that limit by changing the value in PCI_EXP_LNKCAP. Is
> > > > your PORT_LOGIC_GEN3_EQ_DISABLE approach and alternative to the
> > > > PCI_EXP_LNKCAP approach, or does your approach add something else?
> > > >
> > >
> > > No, max speed will be still as per advertised by link or it will be
> > > equal to the limited speed as per DT property if any.
> > > This register will prohibit to perform all phases of equalization and
> > > thus allowing link to happen in maximum supported/advertised speed.
> > >
> > > This is not to limit max link speed, this register helps link to
> > > happen in higher speeds (GEN3/4) without going through equalization
> > > phases. It is intended to use only if at all link fails to latch up in
> > > GEN3/4 due to failure in equalization phases.
> > 
> > I thought that for GEN3 and beyond equalization was *required* - with only
> > phases 2 and 3 being optional. Therefore I'm suprised to see that if
> equalization
> > does fail we continue to train the link anyway. Have I understood this
> correctly?
> > 
> 
> AFAIK, equalization is not mandatory for GEN3 and higher speed. I mean in
> case there is some H/W issue we can still go ahead and disable complete
> equalization.

Regardless, the hardware supports it and I guess you have a need for it.

> 
> > Also are there any plans to provide patches to use this quirk on any
> drivers?
> > 
> 
> Yes, we have plans and soon the user driver of this feature will land for
> review. But I believe this should not be blocker to consider this patch, as
> it is a feature provided in Designware H/W and so we can add S/W support for
> the same.

OK will look forward to seeing that.

Perhaps Gustavo will give his comment on this when he catches up with his
mail.

> 
> > >
> > > > >
> > > > > Platform drivers can disable equalization by setting the
> > > > > dwc_pci_quirk flag DWC_EQUALIZATION_DISABLE.
> > > > >
> > > > > Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> > > > > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > > > > ---
> > > > >  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
> > > > > drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
> > > > >  2 files changed, 14 insertions(+)
> > > > >
> > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > > > > b/drivers/pci/controller/dwc/pcie-designware.c
> > > > > index 7d25102..bf82091 100644
> > > > > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > > > > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > > > > @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
> > > > >               break;
> > > > >       }
> > > > >       dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> > > > > +
> > > > > +     val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > > > +
> > > > > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> > > > > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > > > +
> > > > > +     dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > > >
> > > > The problem here is that even when DWC_EQUALIZATION_DISABLE is not
> > > > set the driver will read and write PCIE_PORT_GEN3_RELATED when it is
> > > > not needed. How about something like:
> > > >
> > > > > +
> > > > > +     if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) {
> > > > > +             val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > > > +             val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > > > +             dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > > > > +     }
> > > >
> > >
> > > Yes, before posting we taught about it, but then next patchset is
> > > adding one more quirk and in that case we need to repeat read and
> > > write under each if condition. I hope that repetition should be fine.
> > 
> > I understand. I think the repetition is prefered over needlessly reading
> and
> > writing registers.
> > 
> 
> OK, will handle this in v2.
> 
> > Given these quirks are so similar, I wouldn't have a problem with them
> being in
> > the same patch.
> > 
> 
> I still prefer to keep these in two separate patches, unless until it is
> something mandatory.

OK, it was just a suggestion.

Thanks,

Andrew Murray

> 
> > Thanks,
> > 
> > Andrew Murray
> > 
> > >
> > > > >  }
> > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware.h
> > > > > b/drivers/pci/controller/dwc/pcie-designware.h
> > > > > index ffed084..a1453c5 100644
> > > > > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > > > > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > > > > @@ -29,6 +29,9 @@
> > > > >  #define LINK_WAIT_MAX_IATU_RETRIES   5
> > > > >  #define LINK_WAIT_IATU                       9
> > > > >
> > > > > +/* Parameters for PCIe Quirks */
> > > > > +#define DWC_EQUALIZATION_DISABLE     0x1
> > > >
> > > > How about using BIT(1) instead? Thus implying that you can combine
> > > > quirks.
> > > >
> > >
> > > Agreed.
> > >
> > > > Thanks,
> > > >
> > > > Andrew Murray
> > > >
> > > > > +
> > > > >  /* Synopsys-specific PCIe configuration registers */
> > > > >  #define PCIE_PORT_LINK_CONTROL               0x710
> > > > >  #define PORT_LINK_MODE_MASK          GENMASK(21, 16)
> > > > > @@ -60,6 +63,9 @@
> > > > >  #define PCIE_MSI_INTR0_MASK          0x82C
> > > > >  #define PCIE_MSI_INTR0_STATUS                0x830
> > > > >
> > > > > +#define PCIE_PORT_GEN3_RELATED               0x890
> > > > > +#define PORT_LOGIC_GEN3_EQ_DISABLE   BIT(16)
> > > > > +
> > > > >  #define PCIE_ATU_VIEWPORT            0x900
> > > > >  #define PCIE_ATU_REGION_INBOUND              BIT(31)
> > > > >  #define PCIE_ATU_REGION_OUTBOUND     0
> > > > > @@ -244,6 +250,7 @@ struct dw_pcie {
> > > > >       struct dw_pcie_ep       ep;
> > > > >       const struct dw_pcie_ops *ops;
> > > > >       unsigned int            version;
> > > > > +     unsigned int            dwc_pci_quirk;
> > > > >  };
> > > > >
> > > > >  #define to_dw_pcie_from_pp(port) container_of((port), struct
> > > > > dw_pcie, pp)
> > > > > --
> > > > > 2.7.4
> > > > >
>
Gustavo Pimentel Sept. 12, 2019, 2:21 p.m. UTC | #6
Hi,

On Tue, Sep 10, 2019 at 13:25:1, Pankaj Dubey <pankaj.dubey@samsung.com> 
wrote:

> From: Anvesh Salveru <anvesh.s@samsung.com>
> 
> In some platforms, PCIe PHY may have issues which will prevent linkup
> to happen in GEN3 or high speed. In case equalization fails, link will
> fallback to GEN1.
> 
> Designware controller has support for disabling GEN3 equalization if
> required. This patch enables the designware driver to disable the PCIe
> GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.

s/Designware/DesignWare
s/designware/DesignWare

> 
> Platform drivers can disable equalization by setting the dwc_pci_quirk
> flag DWC_EQUALIZATION_DISABLE.
> 
> Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
>  drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 7d25102..bf82091 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
>  		break;
>  	}
>  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> +
> +	val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> +
> +	if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> +
> +	dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index ffed084..a1453c5 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -29,6 +29,9 @@
>  #define LINK_WAIT_MAX_IATU_RETRIES	5
>  #define LINK_WAIT_IATU			9
>  
> +/* Parameters for PCIe Quirks */
> +#define DWC_EQUALIZATION_DISABLE	0x1
> +
>  /* Synopsys-specific PCIe configuration registers */
>  #define PCIE_PORT_LINK_CONTROL		0x710
>  #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
> @@ -60,6 +63,9 @@
>  #define PCIE_MSI_INTR0_MASK		0x82C
>  #define PCIE_MSI_INTR0_STATUS		0x830
>  
> +#define PCIE_PORT_GEN3_RELATED		0x890
> +#define PORT_LOGIC_GEN3_EQ_DISABLE	BIT(16)
> +
>  #define PCIE_ATU_VIEWPORT		0x900
>  #define PCIE_ATU_REGION_INBOUND		BIT(31)
>  #define PCIE_ATU_REGION_OUTBOUND	0
> @@ -244,6 +250,7 @@ struct dw_pcie {
>  	struct dw_pcie_ep	ep;
>  	const struct dw_pcie_ops *ops;
>  	unsigned int		version;
> +	unsigned int		dwc_pci_quirk;

I'd prefer called this variable just quirk, the prefix is redundant here.

>  };
>  
>  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> -- 
> 2.7.4

I understand your idea and I'm fine with it, but I just wonder if there 
isn't any other typical way to do this kind of quirks... I'm not seeing a 
similar case to this although.
For me makes more sense to squash both patches (1 and 2), since we aim to 
add this quirk especially because it focuses is on this "GEN3_RELATED" 
register in a logical patch.

Regards,
Gustavo
Pankaj Dubey Sept. 13, 2019, 10:53 a.m. UTC | #7
> -----Original Message-----
> From: Gustavo Pimentel <Gustavo.Pimentel@synopsys.com>
> Sent: Thursday, September 12, 2019 7:52 PM
> To: Pankaj Dubey <pankaj.dubey@samsung.com>; linux-pci@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Cc: jingoohan1@gmail.com; Gustavo.Pimentel@synopsys.com;
> lorenzo.pieralisi@arm.com; bhelgaas@google.com; Anvesh Salveru
> <anvesh.s@samsung.com>
> Subject: RE: [PATCH 1/2] PCI: dwc: Add support to disable GEN3 equalization
> 
> Hi,
> 
> On Tue, Sep 10, 2019 at 13:25:1, Pankaj Dubey <pankaj.dubey@samsung.com>
> wrote:
> 
> > From: Anvesh Salveru <anvesh.s@samsung.com>
> >
> > In some platforms, PCIe PHY may have issues which will prevent linkup
> > to happen in GEN3 or high speed. In case equalization fails, link will
> > fallback to GEN1.
> >
> > Designware controller has support for disabling GEN3 equalization if
> > required. This patch enables the designware driver to disable the PCIe
> > GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED.
> 
> s/Designware/DesignWare
> s/designware/DesignWare
> 
> >
> > Platform drivers can disable equalization by setting the dwc_pci_quirk
> > flag DWC_EQUALIZATION_DISABLE.
> >
> > Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
> > drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++
> >  2 files changed, 14 insertions(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > b/drivers/pci/controller/dwc/pcie-designware.c
> > index 7d25102..bf82091 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
> >  		break;
> >  	}
> >  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> > +
> > +	val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > +
> > +	if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> > +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > +
> > +	dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> >  }
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.h
> > b/drivers/pci/controller/dwc/pcie-designware.h
> > index ffed084..a1453c5 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > @@ -29,6 +29,9 @@
> >  #define LINK_WAIT_MAX_IATU_RETRIES	5
> >  #define LINK_WAIT_IATU			9
> >
> > +/* Parameters for PCIe Quirks */
> > +#define DWC_EQUALIZATION_DISABLE	0x1
> > +
> >  /* Synopsys-specific PCIe configuration registers */
> >  #define PCIE_PORT_LINK_CONTROL		0x710
> >  #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
> > @@ -60,6 +63,9 @@
> >  #define PCIE_MSI_INTR0_MASK		0x82C
> >  #define PCIE_MSI_INTR0_STATUS		0x830
> >
> > +#define PCIE_PORT_GEN3_RELATED		0x890
> > +#define PORT_LOGIC_GEN3_EQ_DISABLE	BIT(16)
> > +
> >  #define PCIE_ATU_VIEWPORT		0x900
> >  #define PCIE_ATU_REGION_INBOUND		BIT(31)
> >  #define PCIE_ATU_REGION_OUTBOUND	0
> > @@ -244,6 +250,7 @@ struct dw_pcie {
> >  	struct dw_pcie_ep	ep;
> >  	const struct dw_pcie_ops *ops;
> >  	unsigned int		version;
> > +	unsigned int		dwc_pci_quirk;
> 
> I'd prefer called this variable just quirk, the prefix is redundant here.
> 
> >  };
> >
> >  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie,
> > pp)
> > --
> > 2.7.4
> 
> I understand your idea and I'm fine with it, but I just wonder if there isn't any
> other typical way to do this kind of quirks... I'm not seeing a similar case to this
> although.

Even we didn't see any existing approach to address this.

> For me makes more sense to squash both patches (1 and 2), since we aim to add
> this quirk especially because it focuses is on this "GEN3_RELATED"
> register in a logical patch.
>

Done. Posted [v2] where we squashed both the patches.
v2: https://lkml.org/lkml/2019/9/13/171

Thanks for review.
 
> Regards,
> Gustavo

Patch
diff mbox series

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 7d25102..bf82091 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -466,4 +466,11 @@  void dw_pcie_setup(struct dw_pcie *pci)
 		break;
 	}
 	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
+
+	val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
+
+	if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
+		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
+
+	dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
 }
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ffed084..a1453c5 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -29,6 +29,9 @@ 
 #define LINK_WAIT_MAX_IATU_RETRIES	5
 #define LINK_WAIT_IATU			9
 
+/* Parameters for PCIe Quirks */
+#define DWC_EQUALIZATION_DISABLE	0x1
+
 /* Synopsys-specific PCIe configuration registers */
 #define PCIE_PORT_LINK_CONTROL		0x710
 #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
@@ -60,6 +63,9 @@ 
 #define PCIE_MSI_INTR0_MASK		0x82C
 #define PCIE_MSI_INTR0_STATUS		0x830
 
+#define PCIE_PORT_GEN3_RELATED		0x890
+#define PORT_LOGIC_GEN3_EQ_DISABLE	BIT(16)
+
 #define PCIE_ATU_VIEWPORT		0x900
 #define PCIE_ATU_REGION_INBOUND		BIT(31)
 #define PCIE_ATU_REGION_OUTBOUND	0
@@ -244,6 +250,7 @@  struct dw_pcie {
 	struct dw_pcie_ep	ep;
 	const struct dw_pcie_ops *ops;
 	unsigned int		version;
+	unsigned int		dwc_pci_quirk;
 };
 
 #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)