[v2,2/2] PCI: qcom: Restrict pci transactions after pci suspend

If the endpoint device state is D0 and irq's are not freed, then
kernel try to mask interrupts by writing in to the vector
table (for MSIX interrupts) and config space (for MSI's).

These transactions are initiated after clocks are getting disabled
as part of PM suspend call. Due to it, these transactions are
resulting in un-clocked access and eventual to crashes.

So added a logic in qcom driver to restrict the unclocked access.
And updated the logic to check the link state before masking
or unmasking the interrupts.

Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 14 +++++++--
 drivers/pci/controller/dwc/pcie-qcom.c            | 35 +++++++++++++++++++++--
 2 files changed, 45 insertions(+), 4 deletions(-)

On Wed, Jun 29, 2022 at 03:03:34PM +0530, Krishna chaitanya chundru wrote:
> If the endpoint device state is D0 and irq's are not freed, then
> kernel try to mask interrupts by writing in to the vector
> table (for MSIX interrupts) and config space (for MSI's).
> 
> These transactions are initiated after clocks are getting disabled
> as part of PM suspend call. Due to it, these transactions are
> resulting in un-clocked access and eventual to crashes.
> 
> So added a logic in qcom driver to restrict the unclocked access.
> And updated the logic to check the link state before masking
> or unmasking the interrupts.
> 

No other PCI driver is doing the DBI access restriction. So this makes me feel
that the fix is somewhere else.

I'll dig into it and come back.

Thanks,
Mani

> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 14 +++++++--
>  drivers/pci/controller/dwc/pcie-qcom.c            | 35 +++++++++++++++++++++--
>  2 files changed, 45 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 2fa86f3..2a46b40 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -29,13 +29,23 @@ static void dw_msi_ack_irq(struct irq_data *d)
>  
>  static void dw_msi_mask_irq(struct irq_data *d)
>  {
> -	pci_msi_mask_irq(d);
> +	struct pcie_port *pp = irq_data_get_irq_chip_data(d->parent_data);
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +
> +	if (dw_pcie_link_up(pci))
> +		pci_msi_mask_irq(d);
> +
>  	irq_chip_mask_parent(d);
>  }
>  
>  static void dw_msi_unmask_irq(struct irq_data *d)
>  {
> -	pci_msi_unmask_irq(d);
> +	struct pcie_port *pp = irq_data_get_irq_chip_data(d->parent_data);
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +
> +	if (dw_pcie_link_up(pci))
> +		pci_msi_unmask_irq(d);
> +
>  	irq_chip_unmask_parent(d);
>  }
>  
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 8e9ef37..227bc24a 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1331,12 +1331,41 @@ static int qcom_pcie_disable_clks_2_7_0(struct qcom_pcie *pcie)
>  	return 0;
>  }
>  
> +static u32 qcom_pcie_read_dbi(struct dw_pcie *pci, void __iomem *base,
> +				u32 reg, size_t size)
> +{
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +	u32 val;
> +
> +	if (pcie->is_suspended)
> +		return PCIBIOS_BAD_REGISTER_NUMBER;
> +
> +	dw_pcie_read(base + reg, size, &val);
> +	return val;
> +}
> +
> +static void qcom_pcie_write_dbi(struct dw_pcie *pci, void __iomem *base,
> +					u32 reg, size_t size, u32 val)
> +{
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +
> +	if (pcie->is_suspended)
> +		return;
> +
> +	dw_pcie_write(base + reg, size, val);
> +}
>  
>  static int qcom_pcie_link_up(struct dw_pcie *pci)
>  {
> -	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> -	u16 val = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +	u16 offset;
> +	u16 val;
> +
> +	if (pcie->is_suspended)
> +		return false;
>  
> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	val = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
>  	return !!(val & PCI_EXP_LNKSTA_DLLLA);
>  }
>  
> @@ -1580,6 +1609,8 @@ static const struct qcom_pcie_cfg sc7280_cfg = {
>  static const struct dw_pcie_ops dw_pcie_ops = {
>  	.link_up = qcom_pcie_link_up,
>  	.start_link = qcom_pcie_start_link,
> +	.read_dbi = qcom_pcie_read_dbi,
> +	.write_dbi = qcom_pcie_write_dbi,
>  };
>  
>  static int qcom_pcie_probe(struct platform_device *pdev)
> -- 
> 2.7.4
>