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

[Ulf Hansson]

On Sun, 17 Oct 2021 at 10:38, Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
>
> 01.10.2021 18:01, Ulf Hansson пишет:
> > 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?
>
> This driver doesn't support active power management. I don't have Tegra
> hardware that uses NAND storage for testing, so it's up to somebody else
> to implement dynamic power management. NAND doesn't require high
> voltages, so it's fine to keep the old driver behaviour by keeping
> hardware resumed since the probe time.

Alright, fair enough and thanks for clarifying!

Kind regards
Uffe