On 12/04/2018 17:24, Mauro Carvalho Chehab wrote:

> As warned by smatch:
>       drivers/media/rc/st_rc.c:110 st_rc_rx_interrupt() warn: this loop 
> depends on readl() succeeding
> 
> If something goes wrong at readl(), the logic will stay there
> inside an IRQ code forever. This is not the nicest thing to
> do :-)
> 
> So, add a timeout there, preventing staying inside the IRQ
> for more than 10ms.
> 
> Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
> ---
>  drivers/media/rc/st_rc.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/rc/st_rc.c b/drivers/media/rc/st_rc.c
> index d2efd7b2c3bc..c855b177103c 100644
> --- a/drivers/media/rc/st_rc.c
> +++ b/drivers/media/rc/st_rc.c
> @@ -96,19 +96,24 @@ static void st_rc_send_lirc_timeout(struct rc_dev *rdev)
>  
>  static irqreturn_t st_rc_rx_interrupt(int irq, void *data)
>  {
> +     unsigned long timeout;
>       unsigned int symbol, mark = 0;
>       struct st_rc_device *dev = data;
>       int last_symbol = 0;
> -     u32 status;
> +     u32 status, int_status;
>       DEFINE_IR_RAW_EVENT(ev);
>  
>       if (dev->irq_wake)
>               pm_wakeup_event(dev->dev, 0);
>  
> -     status  = readl(dev->rx_base + IRB_RX_STATUS);
> +     /* FIXME: is 10ms good enough ? */
> +     timeout = jiffies +  msecs_to_jiffies(10);
> +     do {
> +             status  = readl(dev->rx_base + IRB_RX_STATUS);
> +             if (!(status & (IRB_FIFO_NOT_EMPTY | IRB_OVERFLOW)))
> +                     break;
>  
> -     while (status & (IRB_FIFO_NOT_EMPTY | IRB_OVERFLOW)) {
> -             u32 int_status = readl(dev->rx_base + IRB_RX_INT_STATUS);
> +             int_status = readl(dev->rx_base + IRB_RX_INT_STATUS);
>               if (unlikely(int_status & IRB_RX_OVERRUN_INT)) {
>                       /* discard the entire collection in case of errors!  */
>                       ir_raw_event_reset(dev->rdev);
> @@ -148,8 +153,7 @@ static irqreturn_t st_rc_rx_interrupt(int irq, void *data)
>  
>               }
>               last_symbol = 0;
> -             status  = readl(dev->rx_base + IRB_RX_STATUS);
> -     }
> +     } while (time_is_after_jiffies(timeout));
>  
>       writel(IRB_RX_INTS, dev->rx_base + IRB_RX_INT_CLEAR);
>  

Isn't this a place where the iopoll.h helpers might be useful?

e.g. readl_poll_timeout()

https://elixir.bootlin.com/linux/latest/source/include/linux/iopoll.h#L114

Regards.

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