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

Manivannan Sadhasivam
2024-01-29T16:00:24Z

On Fri, Jan 12, 2024 at 07:52:05PM +0530, Krishna chaitanya chundru 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.
>

s/processors/clients

> 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@quicinc.com>
> ---
> 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;
> + break;
> + }

This switch case is PCIe generic, so need to be moved to drivers/pci/pci.c.
There is already an API, pcie_link_speed_mbps() that returns the frequency in
MBps but uses the pcie_capability_read_word() API to read LNKSTA of the device.

But you can move the switch case inside that API to a separate function and
reuse that here.

> +
> + 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;
> + }
> +
> + /* vote for max freq in the opp table if opp table is present */

/*
* Use highest OPP here if the OPP table is present. At the end of the probe(),
* OPP will be updated using qcom_pcie_icc_opp_update().
*/

- Mani

--
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