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

[Krishna Chaitanya Chundru <quic_krichai@xxxxxxxxxxx>]

On 1/12/2024 9:00 PM, Dmitry Baryshkov wrote:
> On Fri, 12 Jan 2024 at 16:24, Krishna chaitanya chundru
> <quic_krichai@xxxxxxxxxxx> 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.

- Krishna Chaitanya.
> > In suspend remove the cpu vote after register space access is done.
> >
> > Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support")
> > cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
> > ---
> >   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