Re: [PATCH AUTOSEL 5.2 51/59] drm/exynos: fix missing decrement of retry counter

[Sasha Levin]

On Wed, Aug 07, 2019 at 08:49:52AM +0000, David Laight wrote:
> From: Sasha Levin
> > Sent: 06 August 2019 22:33
> >
> > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >
> > [ Upstream commit 1bbbab097a05276e312dd2462791d32b21ceb1ee ]
> >
> > Currently the retry counter is not being decremented, leading to a
> > potential infinite spin if the scalar_reads don't change state.
> >
> > Addresses-Coverity: ("Infinite loop")
> > Fixes: 280e54c9f614 ("drm/exynos: scaler: Reset hardware before starting the operation")
> > Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/exynos/exynos_drm_scaler.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/exynos/exynos_drm_scaler.c b/drivers/gpu/drm/exynos/exynos_drm_scaler.c
> > index ec9c1b7d31033..8989f8af716b7 100644
> > --- a/drivers/gpu/drm/exynos/exynos_drm_scaler.c
> > +++ b/drivers/gpu/drm/exynos/exynos_drm_scaler.c
> > @@ -94,12 +94,12 @@ static inline int scaler_reset(struct scaler_context *scaler)
> >  	scaler_write(SCALER_CFG_SOFT_RESET, SCALER_CFG);
> >  	do {
> >  		cpu_relax();
> > -	} while (retry > 1 &&
> > +	} while (--retry > 1 &&
> >  		 scaler_read(SCALER_CFG) & SCALER_CFG_SOFT_RESET);
> >  	do {
> >  		cpu_relax();
> >  		scaler_write(1, SCALER_INT_EN);
> > -	} while (retry > 0 && scaler_read(SCALER_INT_EN) != 1);
> > +	} while (--retry > 0 && scaler_read(SCALER_INT_EN) != 1);
> >
> >  	return retry ? 0 : -EIO;
>
> If the first loop hits the retry limit the second loop won't be right
> and the final return value will be 0.

This looks like an upstream problem as well, no?

--
Thanks,
Sasha