* Re: drm/exynos: scaler: Reset hardware before starting the operation (bug report)
@ 2019-07-05 16:09 ` Colin Ian King
2019-07-22 17:05 ` Marek Szyprowski
0 siblings, 1 reply; 2+ messages in thread
From: Colin Ian King @ 2019-07-05 16:09 UTC (permalink / raw)
To: Andrzej Pietrasiewicz, Marek Szyprowski, Inki Dae, linux-samsung-soc
Cc: linux-kernel
Hi,
Static analysis on today's linux-next has found a potential error in the
following commit:
commit 280e54c9f614c88292685383cf2d65057586e9fb
Author: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Date: Thu Jun 7 13:06:08 2018 +0200
drm/exynos: scaler: Reset hardware before starting the operation
In the following code the retry counter does not appear to be
decremented, so potentially the loop could get stuck forever if the H/W
does not change state:
static inline int scaler_reset(struct scaler_context *scaler)
{
int retry = SCALER_RESET_WAIT_RETRIES;
scaler_write(SCALER_CFG_SOFT_RESET, SCALER_CFG);
do {
cpu_relax();
} 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);
return retry ? 0 : -EIO;
}
Maybe I'm missing something here subtle.
Colin
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: drm/exynos: scaler: Reset hardware before starting the operation (bug report)
2019-07-05 16:09 ` drm/exynos: scaler: Reset hardware before starting the operation (bug report) Colin Ian King
@ 2019-07-22 17:05 ` Marek Szyprowski
0 siblings, 0 replies; 2+ messages in thread
From: Marek Szyprowski @ 2019-07-22 17:05 UTC (permalink / raw)
To: Colin Ian King, Andrzej Pietrasiewicz, Inki Dae, linux-samsung-soc
Cc: linux-kernel
Hi,
On 2019-07-05 18:09, Colin Ian King wrote:
> Static analysis on today's linux-next has found a potential error in the
> following commit:
>
> commit 280e54c9f614c88292685383cf2d65057586e9fb
> Author: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> Date: Thu Jun 7 13:06:08 2018 +0200
>
> drm/exynos: scaler: Reset hardware before starting the operation
>
> In the following code the retry counter does not appear to be
> decremented, so potentially the loop could get stuck forever if the H/W
> does not change state:
>
> static inline int scaler_reset(struct scaler_context *scaler)
> {
> int retry = SCALER_RESET_WAIT_RETRIES;
>
> scaler_write(SCALER_CFG_SOFT_RESET, SCALER_CFG);
> do {
> cpu_relax();
> } 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);
>
> return retry ? 0 : -EIO;
> }
>
> Maybe I'm missing something here subtle.
Right. Indeed there is missing decrementation of the 'retry' variable. I
suggest to add it to both loops and reset retry value to
SCALER_RESET_WAIT_RETRIES between them.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-07-05 16:09 ` drm/exynos: scaler: Reset hardware before starting the operation (bug report) Colin Ian King
2019-07-22 17:05 ` Marek Szyprowski
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