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

Dmitry Baryshkov
2024-01-12T15:30:46Z

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.

>
> 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
>
>

--
With best wishes
Dmitry