Re: [Linux-ATM-General] [PATCH] atm: idt77252: Replace mdelay with usleep_range in idt77252_preset

[Chas W. <3c...@gm...>]

On Thu, Jan 25, 2018 at 10:42 PM, Jia-Ju Bai <bai...@gm...> wrote:

> After checking all possible call chains to idt77252_preset() here,
> my tool finds that idt77252_preset() is never called in atomic context,
> namely never in an interrupt handler or holding a spinlock.
> And idt77252_preset() calls deinit_card, which calls free_irq (can sleep),
> so it indicates that idt77252_preset() can call functions which can sleep.
> Thus mdelay can be replaced with usleep_range to avoid busy wait.
>
> This is found by a static analysis tool named DCNS written by myself.
>
> Signed-off-by: Jia-Ju Bai <bai...@gm...>
> ---
>  drivers/atm/idt77252.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/atm/idt77252.c b/drivers/atm/idt77252.c
> index 0277f36..cea4bf2 100644
> --- a/drivers/atm/idt77252.c
> +++ b/drivers/atm/idt77252.c
> @@ -3563,7 +3563,7 @@ static int idt77252_preset(struct idt77252_dev *card)
>
>         /* Software reset */
>         writel(SAR_CFG_SWRST, SAR_REG_CFG);
> -       mdelay(1);
> +       usleep_range(500, 1000);
>

Yes, this is a sleepable context.  I would err on the side of caution here
and choose a range
that is a minimum of 1ms instead of 0.5ms.


>         writel(0, SAR_REG_CFG);
>
>         IPRINTK("%s: Software resetted.\n", card->name);
> --
> 1.7.9.5
>
>