Re: [PATCH v13 20/35] mtd: rawnand: tegra: Add runtime PM and OPP support

[Ulf Hansson]

On Fri, 1 Oct 2021 at 16:35, Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
>
> 01.10.2021 17:24, Ulf Hansson пишет:
> > On Mon, 27 Sept 2021 at 00:42, Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
> >>
> >> The NAND on Tegra belongs to the core power domain and we're going to
> >> enable GENPD support for the core domain. Now NAND must be resumed using
> >> runtime PM API in order to initialize the NAND power state. Add runtime PM
> >> and OPP support to the NAND driver.
> >>
> >> Acked-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> >> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
> >> ---
> >>  drivers/mtd/nand/raw/tegra_nand.c | 55 ++++++++++++++++++++++++++-----
> >>  1 file changed, 47 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drivers/mtd/nand/raw/tegra_nand.c b/drivers/mtd/nand/raw/tegra_nand.c
> >> index 32431bbe69b8..098fcc9cb9df 100644
> >> --- a/drivers/mtd/nand/raw/tegra_nand.c
> >> +++ b/drivers/mtd/nand/raw/tegra_nand.c
> >> @@ -17,8 +17,11 @@
> >>  #include <linux/mtd/rawnand.h>
> >>  #include <linux/of.h>
> >>  #include <linux/platform_device.h>
> >> +#include <linux/pm_runtime.h>
> >>  #include <linux/reset.h>
> >>
> >> +#include <soc/tegra/common.h>
> >> +
> >>  #define COMMAND                                        0x00
> >>  #define   COMMAND_GO                           BIT(31)
> >>  #define   COMMAND_CLE                          BIT(30)
> >> @@ -1151,6 +1154,7 @@ static int tegra_nand_probe(struct platform_device *pdev)
> >>                 return -ENOMEM;
> >>
> >>         ctrl->dev = &pdev->dev;
> >> +       platform_set_drvdata(pdev, ctrl);
> >>         nand_controller_init(&ctrl->controller);
> >>         ctrl->controller.ops = &tegra_nand_controller_ops;
> >>
> >> @@ -1166,14 +1170,22 @@ static int tegra_nand_probe(struct platform_device *pdev)
> >>         if (IS_ERR(ctrl->clk))
> >>                 return PTR_ERR(ctrl->clk);
> >>
> >> -       err = clk_prepare_enable(ctrl->clk);
> >> +       err = devm_pm_runtime_enable(&pdev->dev);
> >> +       if (err)
> >> +               return err;
> >> +
> >> +       err = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
> >> +       if (err)
> >> +               return err;
> >> +
> >> +       err = pm_runtime_resume_and_get(&pdev->dev);
> >>         if (err)
> >>                 return err;
> >>
> >>         err = reset_control_reset(rst);
> >>         if (err) {
> >>                 dev_err(ctrl->dev, "Failed to reset HW: %d\n", err);
> >> -               goto err_disable_clk;
> >> +               goto err_put_pm;
> >>         }
> >>
> >>         writel_relaxed(HWSTATUS_CMD_DEFAULT, ctrl->regs + HWSTATUS_CMD);
> >> @@ -1188,21 +1200,19 @@ static int tegra_nand_probe(struct platform_device *pdev)
> >>                                dev_name(&pdev->dev), ctrl);
> >>         if (err) {
> >>                 dev_err(ctrl->dev, "Failed to get IRQ: %d\n", err);
> >> -               goto err_disable_clk;
> >> +               goto err_put_pm;
> >>         }
> >>
> >>         writel_relaxed(DMA_MST_CTRL_IS_DONE, ctrl->regs + DMA_MST_CTRL);
> >>
> >>         err = tegra_nand_chips_init(ctrl->dev, ctrl);
> >>         if (err)
> >> -               goto err_disable_clk;
> >> -
> >> -       platform_set_drvdata(pdev, ctrl);
> >> +               goto err_put_pm;
> >>
> >
> > There is no corresponding call pm_runtime_put() here. Is it
> > intentional to always leave the device runtime resumed after ->probe()
> > has succeeded?
> >
> > I noticed you included some comments about this for some other
> > drivers, as those needed more tweaks. Is that also the case for this
> > driver?
>
> Could you please clarify? There is pm_runtime_put() in both probe-error
> and remove() code paths here.

I was not considering the error path of ->probe() (or ->remove()), but
was rather thinking about when ->probe() completes successfully. Then
you keep the device runtime resumed, because you have called
pm_runtime_resume_and_get() for it.

Shouldn't you have a corresponding pm_runtime_put() in ->probe(),
allowing it to be runtime suspended, until the device is really needed
later on. No?

>
> I assume you're meaning pm_runtime_disable(), but this patch uses
> resource-managed devm_pm_runtime_enable(), and thus, explicit disable
> isn't needed.
>
> >>         return 0;
> >>
> >> -err_disable_clk:
> >> -       clk_disable_unprepare(ctrl->clk);
> >> +err_put_pm:
> >> +       pm_runtime_put(ctrl->dev);
> >>         return err;
> >>  }
> >>

[...]

Kind regards
Uffe