The patch below does not apply to the 5.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 5ab7943187f22b572fd12d517bd699771b88ce91 Mon Sep 17 00:00:00 2001
From: Krunoslav Kovac Krunoslav.Kovac@amd.com Date: Thu, 6 Aug 2020 17:54:47 -0400 Subject: [PATCH] drm/amd/display: fix pow() crashing when given base 0
[Why&How] pow(a,x) is implemented as exp(x*log(a)). log(0) will crash. So return 0^x = 0, unless x=0, convention seems to be 0^0 = 1.
Cc: stable@vger.kernel.org Signed-off-by: Krunoslav Kovac Krunoslav.Kovac@amd.com Reviewed-by: Anthony Koo Anthony.Koo@amd.com Acked-by: Rodrigo Siqueira Rodrigo.Siqueira@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com
diff --git a/drivers/gpu/drm/amd/display/include/fixed31_32.h b/drivers/gpu/drm/amd/display/include/fixed31_32.h index 89ef9f6860e5..16df2a485dd0 100644 --- a/drivers/gpu/drm/amd/display/include/fixed31_32.h +++ b/drivers/gpu/drm/amd/display/include/fixed31_32.h @@ -431,6 +431,9 @@ struct fixed31_32 dc_fixpt_log(struct fixed31_32 arg); */ static inline struct fixed31_32 dc_fixpt_pow(struct fixed31_32 arg1, struct fixed31_32 arg2) { + if (arg1.value == 0) + return arg2.value == 0 ? dc_fixpt_one : dc_fixpt_zero; + return dc_fixpt_exp( dc_fixpt_mul( dc_fixpt_log(arg1),