Re: [PATCH v6 6/6] PCI: qcom: Add OPP support to scale performance state of power domain

From: Dmitry Baryshkov
Date: Tue Jan 16 2024 - 04:55:50 EST

On Tue, 16 Jan 2024 at 07:17, Krishna Chaitanya Chundru
<quic_krichai@xxxxxxxxxxx> wrote:
>
>
>
> On 1/12/2024 9:03 PM, Dmitry Baryshkov wrote:
> > On Fri, 12 Jan 2024 at 16:25, Krishna chaitanya chundru
> > <quic_krichai@xxxxxxxxxxx> wrote:
> >>
> >> QCOM Resource Power Manager-hardened (RPMh) is a hardware block which
> >> maintains hardware state of a regulator by performing max aggregation of
> >> the requests made by all of the processors.
> >>
> >> PCIe controller can operate on different RPMh performance state of power
> >> domain based up on the speed of the link. And this performance state varies
> >> from target to target.
> >>
> >> It is manadate to scale the performance state based up on the PCIe speed
> >> link operates so that SoC can run under optimum power conditions.
> >>
> >> Add Operating Performance Points(OPP) support to vote for RPMh state based
> >> upon GEN speed link is operating.
> >>
> >> OPP can handle ICC bw voting also, so move icc bw voting through opp
> >> framework if opp entries are present.
> >>
> >> In PCIe certain gen speeds like GEN1x2 & GEN2X1 or GEN3x2 & GEN4x1 use
> >> same icc bw and has frequency, so use frequency based search to reduce
> >> number of entries in the opp table.
> >>
> >> Don't initialize icc if opp is supported.
> >>
> >> Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
> >> ---
> >> drivers/pci/controller/dwc/pcie-qcom.c | 83 ++++++++++++++++++++++++++++------
> >> 1 file changed, 70 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> >> index 035953f0b6d8..31512dc9d6ff 100644
> >> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> >> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> >> @@ -22,6 +22,7 @@
> >> #include <linux/of.h>
> >> #include <linux/of_gpio.h>
> >> #include <linux/pci.h>
> >> +#include <linux/pm_opp.h>
> >> #include <linux/pm_runtime.h>
> >> #include <linux/platform_device.h>
> >> #include <linux/phy/pcie.h>
> >> @@ -244,6 +245,7 @@ struct qcom_pcie {
> >> const struct qcom_pcie_cfg *cfg;
> >> struct dentry *debugfs;
> >> bool suspended;
> >> + bool opp_supported;
> >> };
> >>
> >> #define to_qcom_pcie(x) dev_get_drvdata((x)->dev)
> >> @@ -1404,16 +1406,14 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
> >> return 0;
> >> }
> >>
> >> -static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
> >> +static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
> >> {
> >> struct dw_pcie *pci = pcie->pci;
> >> - u32 offset, status;
> >> + u32 offset, status, freq;
> >> + struct dev_pm_opp *opp;
> >> int speed, width;
> >> int ret;
> >>
> >> - if (!pcie->icc_mem)
> >> - return;
> >> -
> >> offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> >> status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
> >>
> >> @@ -1424,11 +1424,42 @@ static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
> >> speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
> >> width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
> >>
> >> - ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
> >> - if (ret) {
> >> - dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> >> - ret);
> >> + if (pcie->opp_supported) {
> >> + switch (speed) {
> >> + case 1:
> >> + freq = 2500000;
> >> + break;
> >> + case 2:
> >> + freq = 5000000;
> >> + break;
> >> + case 3:
> >> + freq = 8000000;
> >> + break;
> >> + default:
> >> + WARN_ON_ONCE(1);
> >> + fallthrough;
> >> + case 4:
> >> + freq = 16000000;
> >
> > I expected that this kind of detail goes to the OPP table itself. Can
> > we index the table using the generation instead of frequency?
> >
> In the previous patch also we tried to use index only, but problem using
> index is we can define only GEN speed. As we are voting for the ICC BW
> voting also we need to consider for lane width while configuring this
> path. It is difficult to use index now as we need to consider both gen
> speed and lane width.
> For that reason we moved to frequencies to reduce number of entries in
> OPP table.
> for example if my controller supports GEN1 & GEN2 and MAX lane width is
> 2.
>
> for GEN1x1
> opp-2500000 {
> };
>
> for GEN2x1 & GEN1x2 as both use same frequiences and bandwidth.
> opp-5000000 {
> };
>
> for GEN2x2
> opp-10000000 {
>
> };

Ack. It would be nice to add this as a comment. Something as simple as
'gen1x2 and gen2x1 share the bandwidth value and thus the opp entry'

>
> - Krishna chaitanya.
> >> + break;
> >> + }
> >> +
> >> + opp = dev_pm_opp_find_freq_exact(pci->dev, freq * width, true);
> >> + if (!IS_ERR(opp)) {
> >> + ret = dev_pm_opp_set_opp(pci->dev, opp);
> >> + if (ret)
> >> + dev_err(pci->dev, "Failed to set opp: freq %ld ret %d\n",
> >> + dev_pm_opp_get_freq(opp), ret);
> >> + dev_pm_opp_put(opp);
> >> + }
> >> + } else {
> >> + ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
> >> + if (ret) {
> >> + dev_err(pci->dev, "failed to set interconnect bandwidth for pcie-mem: %d\n",
> >> + ret);
> >> + }
> >> }
> >> +
> >> + return;
> >> }
> >>
> >> static int qcom_pcie_link_transition_count(struct seq_file *s, void *data)
> >> @@ -1471,8 +1502,10 @@ static void qcom_pcie_init_debugfs(struct qcom_pcie *pcie)
> >> static int qcom_pcie_probe(struct platform_device *pdev)
> >> {
> >> const struct qcom_pcie_cfg *pcie_cfg;
> >> + unsigned long max_freq = INT_MAX;
> >> struct device *dev = &pdev->dev;
> >> struct qcom_pcie *pcie;
> >> + struct dev_pm_opp *opp;
> >> struct dw_pcie_rp *pp;
> >> struct resource *res;
> >> struct dw_pcie *pci;
> >> @@ -1539,9 +1572,33 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> >> goto err_pm_runtime_put;
> >> }
> >>
> >> - ret = qcom_pcie_icc_init(pcie);
> >> - if (ret)
> >> + /* OPP table is optional */
> >> + ret = devm_pm_opp_of_add_table(dev);
> >> + if (ret && ret != -ENODEV) {
> >> + dev_err_probe(dev, ret, "Failed to add OPP table\n");
> >> goto err_pm_runtime_put;
> >> + }
> >
> > Can we initialise the table from the driver if it is not found? This
> > will help us by having the common code later on.
> >
> we already icc voting if there is no opp table present in the dts.

Yes. So later we have two different code paths: one for the OPP table
being present and another one for the absent OPP table. My suggestion
is to initialise minimal OPP table by hand and then have a common code
path in qcom_pcie_icc_update().

> So I think this might not be needed.
> Please let me know if you want to use for some other use case.
>
> - Krishna Chaitanya.
> >> +
> >> + /* vote for max freq in the opp table if opp table is present */
> >> + if (ret != -ENODEV) {
> >> + opp = dev_pm_opp_find_freq_floor(dev, &max_freq);
> >> + if (!IS_ERR(opp)) {
> >> + ret = dev_pm_opp_set_opp(dev, opp);
> >> + if (ret)
> >> + dev_err_probe(pci->dev, ret,
> >> + "Failed to set opp: freq %ld\n",
> >> + dev_pm_opp_get_freq(opp));
> >> + dev_pm_opp_put(opp);
> >> + }
> >> + pcie->opp_supported = true;
> >> + }
> >> +
> >> + /* Skip icc init if opp is supported as icc bw vote is handled by opp framework */
> >> + if (!pcie->opp_supported) {
> >> + ret = qcom_pcie_icc_init(pcie);
> >> + if (ret)
> >> + goto err_pm_runtime_put;
> >> + }
> >>
> >> ret = pcie->cfg->ops->get_resources(pcie);
> >> if (ret)
> >> @@ -1561,7 +1618,7 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> >> goto err_phy_exit;
> >> }
> >>
> >> - qcom_pcie_icc_update(pcie);
> >> + qcom_pcie_icc_opp_update(pcie);
> >>
> >> if (pcie->mhi)
> >> qcom_pcie_init_debugfs(pcie);
> >> @@ -1640,7 +1697,7 @@ static int qcom_pcie_resume_noirq(struct device *dev)
> >> pcie->suspended = false;
> >> }
> >>
> >> - qcom_pcie_icc_update(pcie);
> >> + qcom_pcie_icc_opp_update(pcie);
> >>
> >> return 0;
> >> }
> >>
> >> --
> >> 2.42.0
> >>
> >>
> >
> >



--
With best wishes
Dmitry