linux-kernel - Re: [PATCH] mmc: core: Mark mmc_host device with pm_runtime_no

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Date:   Mon, 22 Mar 2021 11:25:23 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     kehuanlin <chgokhl@...il.com>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kehuanlin@...hsemi.com
Subject: Re: [PATCH] mmc: core: Mark mmc_host device with pm_runtime_no_callbacks

On Sat, 20 Mar 2021 at 05:57, kehuanlin <chgokhl@...il.com> wrote:
>
> The rpm_resume() will call parent's resume callback recursively.
> Since mmc_host has no its own pm_runtime callbacks, the mmc devices
> may fail to resume (-ENOSYS in rpm_callback) sometimes. Mark mmc_host
> device with pm_runtime_no_callbacks can fix the issue.

Can you please elaborate more on this? What do you mean by "sometimes"?

More precisely, how do you trigger the rpm_callback() for mmc class
device to return -ENOSYS?

Don't get me wrong, the patch is fine, but I want to understand if it
actually solves a problem for you - or that it's better considered as
an optimization?

Kind regards
Uffe

>
> Signed-off-by: kehuanlin <chgokhl@...il.com>
> ---
>  drivers/mmc/core/host.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 9b89a91b6b47..177bebd9a6c4 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -15,6 +15,7 @@
>  #include <linux/of.h>
>  #include <linux/of_gpio.h>
>  #include <linux/pagemap.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/pm_wakeup.h>
>  #include <linux/export.h>
>  #include <linux/leds.h>
> @@ -480,6 +481,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
>         host->class_dev.class = &mmc_host_class;
>         device_initialize(&host->class_dev);
>         device_enable_async_suspend(&host->class_dev);
> +       pm_runtime_no_callbacks(&host->class_dev);
>
>         if (mmc_gpio_alloc(host)) {
>                 put_device(&host->class_dev);
> --
> 2.30.0
>