Re: [PATCH 2/2] mmc: sunxi: Add runtime_pm support

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Hi Ulf,

On Thu, Dec 21, 2017 at 01:21:51PM +0100, Ulf Hansson wrote:
> On 20 December 2017 at 11:50, Maxime Ripard
> <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
> > So far, even if our card was not in use, we didn't shut down our main
> > clock, which meant that it was still output on the MMC bus.
> >
> > While this obviously means that we could save some power there, it also
> > created issues when it comes with EMC control since we'll have a perfect
> > peak at the card clock rate.
> >
> > Let's implement runtime_pm with autosuspend so that we will shut down the
> > clock when it's not been in use for quite some time.
> >
> > Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/mmc/host/sunxi-mmc.c | 90 ++++++++++++++++++++++++-------------
> >  1 file changed, 60 insertions(+), 30 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> > index 3ce46ebd3488..c6a0bd0e0476 100644
> > --- a/drivers/mmc/host/sunxi-mmc.c
> > +++ b/drivers/mmc/host/sunxi-mmc.c
> > @@ -35,6 +35,7 @@
> >  #include <linux/of_gpio.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/pm_runtime.h>
> >  #include <linux/regulator/consumer.h>
> >  #include <linux/reset.h>
> >  #include <linux/scatterlist.h>
> > @@ -1217,29 +1218,11 @@ static int sunxi_mmc_resource_request(struct sunxi_mmc_host *host,
> >                 return ret;
> >         }
> >
> > -       ret = clk_prepare_enable(host->clk_mmc);
> > -       if (ret) {
> > -               dev_err(&pdev->dev, "Enable mmc clk err %d\n", ret);
> > -               goto error_disable_clk_ahb;
> > -       }
> > -
> > -       ret = clk_prepare_enable(host->clk_output);
> > -       if (ret) {
> > -               dev_err(&pdev->dev, "Enable output clk err %d\n", ret);
> > -               goto error_disable_clk_mmc;
> > -       }
> > -
> > -       ret = clk_prepare_enable(host->clk_sample);
> > -       if (ret) {
> > -               dev_err(&pdev->dev, "Enable sample clk err %d\n", ret);
> > -               goto error_disable_clk_output;
> > -       }
> > -
> 
> Actually, I think you should keep all the above. Perhaps you may want
> to move it to a separate helper function though, which the
> ->runtime_resume() callbacks can invoke as well.
> 
> More reasons to why, see the comment in the ->probe() function.
> 
> >         if (!IS_ERR(host->reset)) {
> >                 ret = reset_control_reset(host->reset);
> >                 if (ret) {
> >                         dev_err(&pdev->dev, "reset err %d\n", ret);
> > -                       goto error_disable_clk_sample;
> > +                       goto error_disable_clk_ahb;
> >                 }
> >         }
> >
> > @@ -1258,12 +1241,6 @@ static int sunxi_mmc_resource_request(struct sunxi_mmc_host *host,
> >  error_assert_reset:
> >         if (!IS_ERR(host->reset))
> >                 reset_control_assert(host->reset);
> > -error_disable_clk_sample:
> > -       clk_disable_unprepare(host->clk_sample);
> > -error_disable_clk_output:
> > -       clk_disable_unprepare(host->clk_output);
> > -error_disable_clk_mmc:
> > -       clk_disable_unprepare(host->clk_mmc);
> >  error_disable_clk_ahb:
> >         clk_disable_unprepare(host->clk_ahb);
> >         return ret;
> > @@ -1280,6 +1257,7 @@ static int sunxi_mmc_probe(struct platform_device *pdev)
> >                 dev_err(&pdev->dev, "mmc alloc host failed\n");
> >                 return -ENOMEM;
> >         }
> > +       platform_set_drvdata(pdev, mmc);
> >
> >         host = mmc_priv(mmc);
> >         host->mmc = mmc;
> > @@ -1340,12 +1318,16 @@ static int sunxi_mmc_probe(struct platform_device *pdev)
> >         if (ret)
> >                 goto error_free_dma;
> >
> > +       pm_runtime_set_autosuspend_delay(&pdev->dev, 50);
> > +       pm_runtime_use_autosuspend(&pdev->dev);
> > +       pm_runtime_enable(&pdev->dev);
> > +
> 
> This means in case you don't have CONFIG_PM set when compiling this
> driver, the clocks will never be enabled using runtime PM.
> 
> I think it's good practice to deal with this, therefore I think you
> should enable the clocks as before, and instead indicate that the
> device is already runtime resumed.
> 
> In other words, before you call pm_runtime_enable(), invoke
> pm_runtime_set_active().

That's a very good point, I'll do that in the next iteration.

> >         ret = mmc_add_host(mmc);
> >         if (ret)
> >                 goto error_free_dma;
> >
> >         dev_info(&pdev->dev, "base:0x%p irq:%u\n", host->reg_base, host->irq);
> > -       platform_set_drvdata(pdev, mmc);
> > +
> >         return 0;
> >
> >  error_free_dma:
> > @@ -1361,27 +1343,75 @@ static int sunxi_mmc_remove(struct platform_device *pdev)
> >         struct sunxi_mmc_host *host = mmc_priv(mmc);
> >
> >         mmc_remove_host(mmc);
> > +       pm_runtime_force_suspend(&pdev->dev);
> 
> Do you need the clocks to be enabled, while calling disable_irq() and
> sunxi_mmc_reset_host()?
>
> In such case you need to call pm_runtime_get_sync() here. Then move
> pm_runtime_force_suspend() a few lines below, and later call
> pm_runtime_put_noidle().

We don't for disable_irq, but we need it for
sunxi_mmc_reset_host. I'll do what you suggest.

> >         disable_irq(host->irq);
> >         sunxi_mmc_reset_host(host);
> >
> >         if (!IS_ERR(host->reset))
> >                 reset_control_assert(host->reset);
> >
> > -       clk_disable_unprepare(host->clk_sample);
> > +       dma_free_coherent(&pdev->dev, PAGE_SIZE, host->sg_cpu, host->sg_dma);
> > +       mmc_free_host(mmc);
> > +
> > +       return 0;
> > +}
> > +
> > +static int sunxi_mmc_runtime_resume(struct device *dev)
> > +{
> > +       struct mmc_host *mmc = dev_get_drvdata(dev);
> > +       struct sunxi_mmc_host *host = mmc_priv(mmc);
> > +       int ret;
> > +
> > +       ret = clk_prepare_enable(host->clk_mmc);
> > +       if (ret) {
> > +               dev_err(dev, "Enable mmc clk err %d\n", ret);
> > +               return ret;
> > +       }
> > +
> > +       ret = clk_prepare_enable(host->clk_output);
> > +       if (ret) {
> > +               dev_err(dev, "Enable output clk err %d\n", ret);
> > +               goto error_disable_clk_mmc;
> > +       }
> > +
> > +       ret = clk_prepare_enable(host->clk_sample);
> > +       if (ret) {
> > +               dev_err(dev, "Enable sample clk err %d\n", ret);
> > +               goto error_disable_clk_output;
> > +       }
> > +
> > +       return 0;
> > +
> > +error_disable_clk_output:
> >         clk_disable_unprepare(host->clk_output);
> > +error_disable_clk_mmc:
> >         clk_disable_unprepare(host->clk_mmc);
> > -       clk_disable_unprepare(host->clk_ahb);
> > +       return ret;
> > +}
> >
> > -       dma_free_coherent(&pdev->dev, PAGE_SIZE, host->sg_cpu, host->sg_dma);
> > -       mmc_free_host(mmc);
> > +static int sunxi_mmc_runtime_suspend(struct device *dev)
> > +{
> > +       struct mmc_host *mmc = dev_get_drvdata(dev);
> > +       struct sunxi_mmc_host *host = mmc_priv(mmc);
> > +
> > +       clk_disable_unprepare(host->clk_sample);
> > +       clk_disable_unprepare(host->clk_output);
> > +       clk_disable_unprepare(host->clk_mmc);
> >
> >         return 0;
> >  }
> >
> > +static const struct dev_pm_ops sunxi_mmc_pm_ops = {
> > +       SET_RUNTIME_PM_OPS(sunxi_mmc_runtime_suspend,
> > +                          sunxi_mmc_runtime_resume,
> > +                          NULL)
> > +};
> > +
> >  static struct platform_driver sunxi_mmc_driver = {
> >         .driver = {
> >                 .name   = "sunxi-mmc",
> >                 .of_match_table = of_match_ptr(sunxi_mmc_of_match),
> > +               .pm = &sunxi_mmc_pm_ops,
> >         },
> >         .probe          = sunxi_mmc_probe,
> >         .remove         = sunxi_mmc_remove,
> > --
> > git-series 0.9.1
> 
> Otherwise this looks good to me!
> 
> BTW, isn't system wide suspend/resume() also important to save power
> for? That's rather simple to implement, after you have enabled runtime
> PM support.

We don't have (unfortunately) any kind of suspend support at the
moment, so I guess that'll come as a single step when we'll have it :)

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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