On 11/11/2024 17:33, Murad Masimov wrote:
If the value of the clock variable is higher than 800000, the value of the
variable m, which is used as a divisor, will remain zero, because
(clock * testp) will be higher than vcomax in every loop iteration, which
leads to skipping every iteration and leaving variable m unmodified.
Clamp value of the clock variable between the lower and the upper limits.
It should be correct, since there is already a similar lower limit check.
I don't think it is correct.
If the clock asked is > 800000, then delta > premitteddelta, and it will
return -EINVAL.
With your patch it will instead configure the clock to 800000 which is
too low for the mode asked and will result in corrupted output.
Best regards,
--
Jocelyn
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: e829d7ef9f17 ("drm/mgag200: Add support for a new rev of G200e")
Signed-off-by: Murad Masimov <m.masimov@xxxxxxxxx>
---
drivers/gpu/drm/mgag200/mgag200_g200se.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/mgag200/mgag200_g200se.c b/drivers/gpu/drm/mgag200/mgag200_g200se.c
index 7a32d3b1d226..4934c27b084e 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200se.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200se.c
@@ -216,8 +216,7 @@ static int mgag200_g200se_04_pixpllc_atomic_check(struct drm_crtc *crtc,
m = n = p = s = 0;
delta = 0xffffffff;
- if (clock < 25000)
- clock = 25000;
+ clock = clamp(clock, 25000L, 800000L);
clock = clock * 2;
/* Permited delta is 0.5% as VESA Specification */
--
2.39.2
