Re: [PATCH] mmc: meson-gx: Convert host->lock to raw spinlock

[Ulf Hansson]

On Mon, Sep 28, 2026 at 6:22 PM Sean Anderson <sanderson@xxxxxxxxx> wrote:
>
>
>
> On 9/28/26 12:17 PM, Ulf Hansson wrote:
> > On Mon, Sep 21, 2026 at 9:14 PM Sean Anderson <sanderson@xxxxxxxxx> wrote:
> >>
> >> The primary handler for IRQF_ONESHOT interrupts is always run without
> >> threading, even on PREEMPT_RT. Therefore, we must use a raw spinlock,
> >> which will never sleep (even on PREEMPT_RT).
> >
> > Sorry, but I don't quite understand the above. Are you saying that
> > IRQF_ONESHOT only works with raw spinlocks?
>
> The primary handler of an IRQF_ONESHOT handler must use raw spinlocks.
>
> https://www.kernel.org/doc/html/latest/core-api/real-time/differences.html#interrupt-handling

Right, thanks for sharing!

Rather than moving to use a raw spinlock, I think a better option
would be to convert the driver into using only a threaded irq handler,
unless there are specific reasons why this can't work.

>
> >
> >>
> >> Fixes: 066ecde6d826 ("mmc: meson-gx: add SDIO interrupt support")
> >> Signed-off-by: Sean Anderson <sanderson@xxxxxxxxx>

Kind regards
Uffe


> >> ---
> >>
> >>   drivers/mmc/host/meson-gx-mmc.c | 12 ++++++------
> >>   1 file changed, 6 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> >> index 694bb443d5f3f..d5365c0404cb9 100644
> >> --- a/drivers/mmc/host/meson-gx-mmc.c
> >> +++ b/drivers/mmc/host/meson-gx-mmc.c
> >> @@ -176,7 +176,7 @@ struct meson_host {
> >>
> >>          bool needs_pre_post_req;
> >>
> >> -       spinlock_t lock;
> >> +       raw_spinlock_t lock;
> >>   };
> >>
> >>   #define CMD_CFG_LENGTH_MASK GENMASK(8, 0)
> >> @@ -953,10 +953,10 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
> >>          cmd = host->cmd;
> >>
> >>          if (status & IRQ_SDIO) {
> >> -               spin_lock(&host->lock);
> >> +               raw_spin_lock(&host->lock);
> >>                  __meson_mmc_enable_sdio_irq(host->mmc, 0);
> >>                  sdio_signal_irq(host->mmc);
> >> -               spin_unlock(&host->lock);
> >> +               raw_spin_unlock(&host->lock);
> >>                  status &= ~IRQ_SDIO;
> >>                  if (!status)
> >>                          return IRQ_HANDLED;
> >> @@ -1112,9 +1112,9 @@ static void meson_mmc_enable_sdio_irq(struct mmc_host *mmc, int enable)
> >>          struct meson_host *host = mmc_priv(mmc);
> >>          unsigned long flags;
> >>
> >> -       spin_lock_irqsave(&host->lock, flags);
> >> +       raw_spin_lock_irqsave(&host->lock, flags);
> >>          __meson_mmc_enable_sdio_irq(mmc, enable);
> >> -       spin_unlock_irqrestore(&host->lock, flags);
> >> +       raw_spin_unlock_irqrestore(&host->lock, flags);
> >>   }
> >>
> >>   static void meson_mmc_ack_sdio_irq(struct mmc_host *mmc)
> >> @@ -1225,7 +1225,7 @@ static int meson_mmc_probe(struct platform_device *pdev)
> >>          if (ret)
> >>                  goto err_init_clk;
> >>
> >> -       spin_lock_init(&host->lock);
> >> +       raw_spin_lock_init(&host->lock);
> >>
> >>          if (host->dram_access_quirk) {
> >>                  /* Limit segments to 1 due to low available sram memory */
> >> ---
> >> base-commit: 587858367581b9c55c3690f4e63382ad622719d4
> >> branch: meson_mmc_raw
> >>
> >> --
> >> 2.53.0
> >>
>