linux-kernel - Re: [PATCH] misc: rtsx: usb: Ensure mmc child device is active when card is present

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Message-ID: <CAPDyKFpmt4eTfBOWphH3LtoW9jAujBs7oAFqqnxkJvP+r83tkw@mail.gmail.com>
Date: Wed, 16 Jul 2025 12:39:15 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Ricky Wu <ricky_wu@...ltek.com>
Cc: linux-kernel@...r.kernel.org, arnd@...db.de, gregkh@...uxfoundation.org, 
	mingo@...nel.org, kai.heng.feng@...onical.com, stable@...r.kernel.org, 
	Gavin Li <gfl3162@...il.com>
Subject: Re: [PATCH] misc: rtsx: usb: Ensure mmc child device is active when
 card is present

+ Gavin

On Fri, 11 Jul 2025 at 16:02, Ricky Wu <ricky_wu@...ltek.com> wrote:
>
> When a card is present in the reader, the driver currently defers
> autosuspend by returning -EAGAIN during the suspend callback to
> trigger USB remote wakeup signaling. However, this does not guarantee
> that the mmc child device has been resumed, which may cause issues if
> it remains suspended while the card is accessible.
> This patch ensures that all child devices, including the mmc host
> controller, are explicitly resumed before returning -EAGAIN. This
> fixes a corner case introduced by earlier remote wakeup handling,
> improving reliability of runtime PM when a card is inserted.
>
> Fixes: 883a87ddf2f1 ("misc: rtsx_usb: Use USB remote wakeup signaling for card insertion detection")
> Cc: stable@...r.kernel.org
> Signed-off-by: Ricky Wu <ricky_wu@...ltek.com>

This seems reasonable to me, but perhaps some of the USB maintainers
should have a closer look to see if this makes sense. Nevertheless,
feel free to add:

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Moreover, we had a related bug-report/fix posted for the
rtsx_usb_sdmmc driver [1] not that long ago. Do you know if $subject
patch solves this problem too? I have looped in Gavin, if he has some
additional comments around this.

Kind regards
Uffe

[1]
https://lore.kernel.org/all/20250510031945.1004129-1-git@thegavinli.com/

> ---
>  drivers/misc/cardreader/rtsx_usb.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/misc/cardreader/rtsx_usb.c b/drivers/misc/cardreader/rtsx_usb.c
> index 148107a4547c..d007a4455ce5 100644
> --- a/drivers/misc/cardreader/rtsx_usb.c
> +++ b/drivers/misc/cardreader/rtsx_usb.c
> @@ -698,6 +698,12 @@ static void rtsx_usb_disconnect(struct usb_interface *intf)
>  }
>
>  #ifdef CONFIG_PM
> +static int rtsx_usb_resume_child(struct device *dev, void *data)
> +{
> +       pm_request_resume(dev);
> +       return 0;
> +}
> +
>  static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
>  {
>         struct rtsx_ucr *ucr =
> @@ -713,8 +719,10 @@ static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
>                         mutex_unlock(&ucr->dev_mutex);
>
>                         /* Defer the autosuspend if card exists */
> -                       if (val & (SD_CD | MS_CD))
> +                       if (val & (SD_CD | MS_CD)) {
> +                               device_for_each_child(&intf->dev, NULL, rtsx_usb_resume_child);
>                                 return -EAGAIN;
> +                       }
>                 } else {
>                         /* There is an ongoing operation*/
>                         return -EAGAIN;
> @@ -724,12 +732,6 @@ static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
>         return 0;
>  }
>
> -static int rtsx_usb_resume_child(struct device *dev, void *data)
> -{
> -       pm_request_resume(dev);
> -       return 0;
> -}
> -
>  static int rtsx_usb_resume(struct usb_interface *intf)
>  {
>         device_for_each_child(&intf->dev, NULL, rtsx_usb_resume_child);
> --
> 2.25.1
>