Re: [PATCH v3 3/3] PCI: qcom: Add OPP support for speed based performance state of RPMH

[Pavan Kondeti <quic_pkondeti@quicinc.com>]

+linux-pm and OPP maintainers

On Tue, Aug 22, 2023 at 09:57:41AM +0530, Krishna Chaitanya Chundru wrote:
> 
> On 8/22/2023 9:33 AM, Pavan Kondeti wrote:
> > On Mon, Aug 21, 2023 at 07:45:43PM +0530, Krishna chaitanya chundru wrote:
> > > Before link training vote for the maximum performance state of RPMH
> > > and once link is up, vote for the performance state based upon the link
> > > speed.
> > > 
> > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> > > ---
> > >   drivers/pci/controller/dwc/pcie-qcom.c | 47 ++++++++++++++++++++++++++++++++++
> > >   1 file changed, 47 insertions(+)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 7a87a47..c57ca1a 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -22,6 +22,7 @@
> > >   #include <linux/of_device.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>
> > > @@ -1357,6 +1358,32 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
> > >   	return 0;
> > >   }
> > > +static void qcom_pcie_opp_update(struct qcom_pcie *pcie)
> > > +{
> > > +	struct dw_pcie *pci = pcie->pci;
> > > +	struct dev_pm_opp *opp;
> > > +	u32 offset, status;
> > > +	int speed, ret = 0;
> > > +
> > > +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > > +	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
> > > +
> > > +	/* Only update constraints if link is up. */
> > > +	if (!(status & PCI_EXP_LNKSTA_DLLLA))
> > > +		return;
> > > +
> > What happens if link is not up during probe? We set max vote before
> > this, should not we bring it down in suspend and vote it back again in
> > resume?
> 
> ok, I will set to lower value in the suspend path if the link is not up.  If
> the link is already up driver will not
> 
> do any modifications.
> 
> > 
> > > +	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
> > > +
> > > +	opp = dev_pm_opp_find_level_exact(pci->dev, speed);
> > > +	if (!IS_ERR(opp)) {
> > > +		ret = dev_pm_opp_set_opp(pci->dev, opp);
> > > +		if (ret)
> > > +			dev_err(pci->dev, "Failed to set opp: %d\n", ret);
> > > +		dev_pm_opp_put(opp);
> > > +	}
> > Since you added an error message, make it more useful by printing the
> > opp level also. dev_pm_opp_get_level().
> Sure I will add this in next patch.
> > 
> > > +
> > > +}
> > > +
> > >   static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
> > >   {
> > >   	struct dw_pcie *pci = pcie->pci;
> > > @@ -1439,8 +1466,10 @@ 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;
> > > @@ -1511,6 +1540,22 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> > >   	if (ret)
> > >   		goto err_pm_runtime_put;
> > > +	/* OPP table is optional */
> > > +	ret = devm_pm_opp_of_add_table(dev);
> > > +	if (ret && ret != -ENODEV) {
> > > +		dev_err(dev, "Invalid OPP table in Device tree\n");
> > > +		goto err_pm_runtime_put;
> > > +	}
> > > +
> > > +	/* vote for max level in the opp table */
> > > +	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(pci->dev, "Failed to set opp: %d\n", ret);
> > > +		dev_pm_opp_put(opp);
> > > +	}
> > > +
> > This needs an update since you moved from frequency based voting to link
> > speed based voting.
> 
> dev_pm_opp_find_freq_floor will give us the max the opp level opp we don't
> have a similar API to get max opp-level
> 
> For that reason we are using this API.
> 

Ok, thanks. I get that it is working. Would you be not knowing the exact
level for the max speed supported? if that is unknown, I believe we have
a use case for dev_pm_opp_find_level_floor() API. Adding the best people
on this matter for thei valuable opinion/suggestions.

Thanks,
Pavan