Re: [PATCH] mmc: omap: synchronize clock timer before disabling fclk

[Ulf Hansson]

On Tue, Sep 29, 2026 at 2:45 PM Runyu Xiao <runyu.xiao@xxxxxxxxxx> wrote:
>
> mmc_omap_select_slot() removes clk_timer with timer_delete() before
> switching slots and changing the functional clock state.  timer_delete()
> only removes a pending timer and does not wait for a callback that is
> already running.
>
> If mmc_omap_clk_timer() is already running, it can therefore call
> mmc_omap_fclk_enable() while the request or slot-switch path changes the
> same clock state.  During host removal, the same window can overlap the
> final clock shutdown.
>
> Use timer_delete_sync() so the callback has completed before slot switching
> or changing the functional clock state.  Keep the timer restartable for
> normal request handling.
>
> Fixes: 0807a9b5739a ("MMC: OMAP: Lazy clock shutdown")
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
> ---
>  drivers/mmc/host/omap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
> index 527b89a5e..02d288e4e 100644
> --- a/drivers/mmc/host/omap.c
> +++ b/drivers/mmc/host/omap.c
> @@ -214,7 +214,7 @@ static void mmc_omap_select_slot(struct mmc_omap_slot *slot, int claimed)
>         host->mmc = slot->mmc;
>         spin_unlock_irqrestore(&host->slot_lock, flags);
>  no_claim:
> -       timer_delete(&host->clk_timer);
> +       timer_delete_sync(&host->clk_timer);

At a first glance this looks fine, but I am slightly worried that this
could deadlock. Have you verified that?

>         if (host->current_slot != slot || !claimed)
>                 mmc_omap_fclk_offdelay(host->current_slot);
>
> @@ -273,7 +273,7 @@ static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
>                 /* Keeps clock running for at least 8 cycles on valid freq */
>                 mod_timer(&host->clk_timer, jiffies  + HZ/10);
>         else {
> -               timer_delete(&host->clk_timer);
> +               timer_delete_sync(&host->clk_timer);

Ditto.

>                 mmc_omap_fclk_offdelay(slot);
>                 mmc_omap_fclk_enable(host, 0);
>         }
> --
> 2.34.1

Kind regards
Uffe