Re: [PATCH v4 6/6] spi: spi-qcom-qspi: Use OPP API to set clk/perf state

[Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>]

On 5/5/2020 10:08 PM, Matthias Kaehlcke wrote:
> Hi Rajendra,
>
> On Sun, May 03, 2020 at 05:34:29PM +0530, Rajendra Nayak wrote:
> > QSPI needs to vote on a performance state of a power domain depending on
> > the clock rate. Add support for it by specifying the perf state/clock rate
> > as an OPP table in device tree.
> >
> > Signed-off-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
> > Cc: Mark Brown <broonie@xxxxxxxxxx>
> > Cc: Alok Chauhan <alokc@xxxxxxxxxxxxxx>
> > Cc: Akash Asthana <akashast@xxxxxxxxxxxxxx>
> > Cc: linux-spi@xxxxxxxxxxxxxxx
> > ---
> >   drivers/spi/spi-qcom-qspi.c | 29 ++++++++++++++++++++++++++++-
> >   1 file changed, 28 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/spi/spi-qcom-qspi.c b/drivers/spi/spi-qcom-qspi.c
> > index 3c4f83b..eb53c00 100644
> > --- a/drivers/spi/spi-qcom-qspi.c
> > +++ b/drivers/spi/spi-qcom-qspi.c
> > @@ -8,6 +8,7 @@
> >   #include <linux/of.h>
> >   #include <linux/of_platform.h>
> >   #include <linux/pm_runtime.h>
> > +#include <linux/pm_opp.h>
> >   #include <linux/spi/spi.h>
> >   #include <linux/spi/spi-mem.h>
> >   
> > @@ -139,6 +140,8 @@ struct qcom_qspi {
> >   	struct device *dev;
> >   	struct clk_bulk_data *clks;
> >   	struct qspi_xfer xfer;
> > +	struct opp_table *opp_table;
> > +	bool has_opp_table;
> >   	/* Lock to protect xfer and IRQ accessed registers */
> >   	spinlock_t lock;
> >   };
> > @@ -235,7 +238,7 @@ static int qcom_qspi_transfer_one(struct spi_master *master,
> >   		speed_hz = xfer->speed_hz;
> >   
> >   	/* In regular operation (SBL_EN=1) core must be 4x transfer clock */
> > -	ret = clk_set_rate(ctrl->clks[QSPI_CLK_CORE].clk, speed_hz * 4);
> > +	ret = dev_pm_opp_set_rate(ctrl->dev, speed_hz * 4);
> >   	if (ret) {
> >   		dev_err(ctrl->dev, "Failed to set core clk %d\n", ret);
> >   		return ret;
> > @@ -481,6 +484,20 @@ static int qcom_qspi_probe(struct platform_device *pdev)
> >   	master->handle_err = qcom_qspi_handle_err;
> >   	master->auto_runtime_pm = true;
> >   
> > +	ctrl->opp_table = dev_pm_opp_set_clkname(&pdev->dev, "core");
> > +	if (IS_ERR(ctrl->opp_table)) {
> > +		ret = PTR_ERR(ctrl->opp_table);
> > +		goto exit_probe_master_put;
> > +	}
> > +	/* OPP table is optional */
> > +	ret = dev_pm_opp_of_add_table(&pdev->dev);
> > +	if (!ret) {
> > +		ctrl->has_opp_table = true;
> > +	} else if (ret != -ENODEV) {
> > +		dev_err(&pdev->dev, "invalid OPP table in device tree\n");
> > +		goto exit_probe_master_put;
> > +	}
> > +
> >   	pm_runtime_enable(dev);
> >   
> >   	ret = spi_register_master(master);
> > @@ -488,6 +505,9 @@ static int qcom_qspi_probe(struct platform_device *pdev)
> >   		return 0;
> >   
> >   	pm_runtime_disable(dev);
> > +	if (ctrl->has_opp_table)
> > +		dev_pm_opp_of_remove_table(&pdev->dev);
> > +	dev_pm_opp_put_clkname(ctrl->opp_table);
> >   
> >   exit_probe_master_put:
> >   	spi_master_put(master);
> > @@ -498,6 +518,11 @@ static int qcom_qspi_probe(struct platform_device *pdev)
> >   static int qcom_qspi_remove(struct platform_device *pdev)
> >   {
> >   	struct spi_master *master = platform_get_drvdata(pdev);
> > +	struct qcom_qspi *ctrl = spi_master_get_devdata(master);
> > +
> > +	if (ctrl->has_opp_table)
> > +		dev_pm_opp_of_remove_table(&pdev->dev);
> > +	dev_pm_opp_put_clkname(ctrl->opp_table);
>
> IIUC there can still be active transfers before the controller is
> unregistered. If that is correct the above should be done after the
> spi_unregister_master() call below.

ah, true. i should have read the comment below :)

> >   
> >   	/* Unregister _before_ disabling pm_runtime() so we stop transfers */
> >   	spi_unregister_master(master);
> > @@ -512,6 +537,8 @@ static int __maybe_unused qcom_qspi_runtime_suspend(struct device *dev)
> >   	struct spi_master *master = dev_get_drvdata(dev);
> >   	struct qcom_qspi *ctrl = spi_master_get_devdata(master);
> >   
> > +	/* Drop the performance state vote */
> > +	dev_pm_opp_set_rate(dev, 0);
> >   	clk_bulk_disable_unprepare(QSPI_NUM_CLKS, ctrl->clks);
> >   
> >   	return 0;

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