| Message ID | 20231010155914.9516-2-manivannan.sadhasivam@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: qcom: Enable ASPM on host bridge and devices | expand |
On Tue, Oct 10, 2023 at 09:29:13PM +0530, Manivannan Sadhasivam wrote: > This callback can be used by the platform drivers to do configuration once > all the devices are scanned. Like changing LNKCTL of all downstream devices > to enable ASPM etc... > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > --- > drivers/pci/controller/dwc/pcie-designware-host.c | 3 +++ > drivers/pci/controller/dwc/pcie-designware.h | 1 + > 2 files changed, 4 insertions(+) > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > index a7170fd0e847..7991f0e179b2 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > @@ -502,6 +502,9 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > if (ret) > goto err_stop_link; > > + if (pp->ops->host_post_init) > + pp->ops->host_post_init(pp); I know we talked about this a little bit in the context of enabling ASPM for devices below qcom 1.9.0 controllers at https://lore.kernel.org/r/20231011050058.GC3508@thinkpad But I didn't realize at the time that this callback adds a fundamental difference between devices present at boot-time (these devices can be affected by this callback) and any devices hot-added later (we never run this callback again, so anything done by .host_post_init() never applies to them). We merged this for now, and it helps enable ASPM for builtin devices on qcom, but I don't feel good about this from a larger DWC perspective. If other drivers use this and they support hot-add, I think we're going to have problems. > return 0; > > err_stop_link: > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > index ef0b2efa9f93..efb4d4754fc8 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -301,6 +301,7 @@ enum dw_pcie_ltssm { > struct dw_pcie_host_ops { > int (*host_init)(struct dw_pcie_rp *pp); > void (*host_deinit)(struct dw_pcie_rp *pp); > + void (*host_post_init)(struct dw_pcie_rp *pp); > int (*msi_host_init)(struct dw_pcie_rp *pp); > void (*pme_turn_off)(struct dw_pcie_rp *pp); > }; > -- > 2.25.1 >
On Mon, Oct 16, 2023 at 03:58:49PM -0500, Bjorn Helgaas wrote: > On Tue, Oct 10, 2023 at 09:29:13PM +0530, Manivannan Sadhasivam wrote: > > This callback can be used by the platform drivers to do configuration once > > all the devices are scanned. Like changing LNKCTL of all downstream devices > > to enable ASPM etc... > > > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > > --- > > drivers/pci/controller/dwc/pcie-designware-host.c | 3 +++ > > drivers/pci/controller/dwc/pcie-designware.h | 1 + > > 2 files changed, 4 insertions(+) > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > index a7170fd0e847..7991f0e179b2 100644 > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > @@ -502,6 +502,9 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > if (ret) > > goto err_stop_link; > > > > + if (pp->ops->host_post_init) > > + pp->ops->host_post_init(pp); > > I know we talked about this a little bit in the context of enabling > ASPM for devices below qcom 1.9.0 controllers at > https://lore.kernel.org/r/20231011050058.GC3508@thinkpad > > But I didn't realize at the time that this callback adds a fundamental > difference between devices present at boot-time (these devices can be > affected by this callback) and any devices hot-added later (we never > run this callback again, so anything done by .host_post_init() never > applies to them). > > We merged this for now, and it helps enable ASPM for builtin devices > on qcom, but I don't feel good about this from a larger DWC > perspective. If other drivers use this and they support hot-add, I > think we're going to have problems. > If someone is going to add same ASPM code in host_post_init() callback, they will most likely aware of the hotplug issue. I see this as an interim solution overall and we should fix the PCI core to handle this. But I do not see any straightforward way to enable ASPM by default in PCI core as the misbehaving devices can pull the system down (atleast in some x86 cases). - Mani
On Tue, Oct 17, 2023 at 01:29:52PM +0530, Manivannan Sadhasivam wrote: > On Mon, Oct 16, 2023 at 03:58:49PM -0500, Bjorn Helgaas wrote: > > On Tue, Oct 10, 2023 at 09:29:13PM +0530, Manivannan Sadhasivam wrote: > > > This callback can be used by the platform drivers to do configuration once > > > all the devices are scanned. Like changing LNKCTL of all downstream devices > > > to enable ASPM etc... > > > > > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > > > --- > > > drivers/pci/controller/dwc/pcie-designware-host.c | 3 +++ > > > drivers/pci/controller/dwc/pcie-designware.h | 1 + > > > 2 files changed, 4 insertions(+) > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > index a7170fd0e847..7991f0e179b2 100644 > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > @@ -502,6 +502,9 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > if (ret) > > > goto err_stop_link; > > > > > > + if (pp->ops->host_post_init) > > > + pp->ops->host_post_init(pp); > > > > I know we talked about this a little bit in the context of enabling > > ASPM for devices below qcom 1.9.0 controllers at > > https://lore.kernel.org/r/20231011050058.GC3508@thinkpad > > > > But I didn't realize at the time that this callback adds a fundamental > > difference between devices present at boot-time (these devices can be > > affected by this callback) and any devices hot-added later (we never > > run this callback again, so anything done by .host_post_init() never > > applies to them). > > > > We merged this for now, and it helps enable ASPM for builtin devices > > on qcom, but I don't feel good about this from a larger DWC > > perspective. If other drivers use this and they support hot-add, I > > think we're going to have problems. > > If someone is going to add same ASPM code in host_post_init() > callback, they will most likely aware of the hotplug issue. I see > this as an interim solution overall and we should fix the PCI core > to handle this. But I do not see any straightforward way to enable > ASPM by default in PCI core as the misbehaving devices can pull the > system down (atleast in some x86 cases). Definitely an interim solution, but the interim is going to be long :) I don't see the PCI core ASPM issue being resolved very soon; it's been this way ever since the beginning. I guess there's no point in me whining without any proposals. Bjorn
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c index a7170fd0e847..7991f0e179b2 100644 --- a/drivers/pci/controller/dwc/pcie-designware-host.c +++ b/drivers/pci/controller/dwc/pcie-designware-host.c @@ -502,6 +502,9 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) if (ret) goto err_stop_link; + if (pp->ops->host_post_init) + pp->ops->host_post_init(pp); + return 0; err_stop_link: diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h index ef0b2efa9f93..efb4d4754fc8 100644 --- a/drivers/pci/controller/dwc/pcie-designware.h +++ b/drivers/pci/controller/dwc/pcie-designware.h @@ -301,6 +301,7 @@ enum dw_pcie_ltssm { struct dw_pcie_host_ops { int (*host_init)(struct dw_pcie_rp *pp); void (*host_deinit)(struct dw_pcie_rp *pp); + void (*host_post_init)(struct dw_pcie_rp *pp); int (*msi_host_init)(struct dw_pcie_rp *pp); void (*pme_turn_off)(struct dw_pcie_rp *pp); };
This callback can be used by the platform drivers to do configuration once all the devices are scanned. Like changing LNKCTL of all downstream devices to enable ASPM etc... Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> --- drivers/pci/controller/dwc/pcie-designware-host.c | 3 +++ drivers/pci/controller/dwc/pcie-designware.h | 1 + 2 files changed, 4 insertions(+)