Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu to PCIe path

[Manivannan Sadhasivam <mani@kernel.org>]

On Tue, Jan 16, 2024 at 10:27:23AM +0530, Krishna Chaitanya Chundru wrote:
> 
> 
> On 1/12/2024 9:00 PM, Dmitry Baryshkov wrote:
> > On Fri, 12 Jan 2024 at 16:24, Krishna chaitanya chundru
> > <quic_krichai@quicinc.com> wrote:
> > > 
> > > CPU-PCIe path consits for registers PCIe BAR space, config space.
> > > As there is less access on this path compared to pcie to mem path
> > > add minimum vote i.e GEN1x1 bandwidth always.
> > 
> > Is this BW amount a real requirement or just a random number? I mean,
> > the register space in my opinion consumes much less bandwidth compared
> > to Gen1 memory access.
> > 
> Not register space right the BAR space and config space access from CPU
> goes through this path only. There is no recommended value we need to
> vote for this path. Keeping BAR space and config space we tried to vote
> for GEN1x1.
> 
> Please suggest any recommended value, I will change that in the next
> series.
> 

You should ask the HW folks on the recommended value to keep the reg access
clocking. We cannot suggest a value here.

If they say, "there is no recommended value", then ask them what would the
minimum value and use it here.

- Mani

> - Krishna Chaitanya.
> > > 
> > > In suspend remove the cpu vote after register space access is done.
> > > 
> > > Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support")
> > > cc: stable@vger.kernel.org
> > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> > > ---
> > >   drivers/pci/controller/dwc/pcie-qcom.c | 31 +++++++++++++++++++++++++++++--
> > >   1 file changed, 29 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 11c80555d975..035953f0b6d8 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -240,6 +240,7 @@ struct qcom_pcie {
> > >          struct phy *phy;
> > >          struct gpio_desc *reset;
> > >          struct icc_path *icc_mem;
> > > +       struct icc_path *icc_cpu;
> > >          const struct qcom_pcie_cfg *cfg;
> > >          struct dentry *debugfs;
> > >          bool suspended;
> > > @@ -1372,6 +1373,9 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
> > >          if (IS_ERR(pcie->icc_mem))
> > >                  return PTR_ERR(pcie->icc_mem);
> > > 
> > > +       pcie->icc_cpu = devm_of_icc_get(pci->dev, "cpu-pcie");
> > > +       if (IS_ERR(pcie->icc_cpu))
> > > +               return PTR_ERR(pcie->icc_cpu);
> > >          /*
> > >           * Some Qualcomm platforms require interconnect bandwidth constraints
> > >           * to be set before enabling interconnect clocks.
> > > @@ -1381,7 +1385,18 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
> > >           */
> > >          ret = icc_set_bw(pcie->icc_mem, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
> > >          if (ret) {
> > > -               dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> > > +               dev_err(pci->dev, "failed to set interconnect bandwidth for pcie-mem: %d\n",
> > > +                       ret);
> > > +               return ret;
> > > +       }
> > > +
> > > +       /*
> > > +        * The config space, BAR space and registers goes through cpu-pcie path.
> > > +        * Set peak bandwidth to single-lane Gen1 for this path all the time.
> > > +        */
> > > +       ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
> > > +       if (ret) {
> > > +               dev_err(pci->dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n",
> > >                          ret);
> > >                  return ret;
> > >          }
> > > @@ -1573,7 +1588,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
> > >           */
> > >          ret = icc_set_bw(pcie->icc_mem, 0, kBps_to_icc(1));
> > >          if (ret) {
> > > -               dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
> > > +               dev_err(dev, "Failed to set interconnect bandwidth for pcie-mem: %d\n", ret);
> > >                  return ret;
> > >          }
> > > 
> > > @@ -1597,6 +1612,12 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
> > >                  pcie->suspended = true;
> > >          }
> > > 
> > > +       /* Remove cpu path vote after all the register access is done */
> > > +       ret = icc_set_bw(pcie->icc_cpu, 0, 0);
> > > +       if (ret) {
> > > +               dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
> > > +               return ret;
> > > +       }
> > >          return 0;
> > >   }
> > > 
> > > @@ -1605,6 +1626,12 @@ static int qcom_pcie_resume_noirq(struct device *dev)
> > >          struct qcom_pcie *pcie = dev_get_drvdata(dev);
> > >          int ret;
> > > 
> > > +       ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
> > > +       if (ret) {
> > > +               dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
> > > +               return ret;
> > > +       }
> > > +
> > >          if (pcie->suspended) {
> > >                  ret = qcom_pcie_host_init(&pcie->pci->pp);
> > >                  if (ret)
> > > 
> > > --
> > > 2.42.0
> > > 
> > > 
> > 
> > 
> 

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