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

[Ulf Hansson]

On 20 December 2017 at 11:50, Maxime Ripard
<maxime.ripard at free-electrons.com> 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 at free-electrons.com>
> ---
>  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().

>         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().

>         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.

Kind regards
Uffe