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drm/amd/display: Fix divide-by-zero in calculate_mcache_setting on zero viewport

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If a plane reaches calculate_mcache_setting with a zero-area viewport,
calculate_mcache_setting exits early with num_mcaches == 0 and
mvmpg_width/height == 0. This will cause a divide-by-zero panic and can
also cause an underflow on num_mcaches.

Fix this by changing calculate_mcache_setting to bool and adding guards
after each calculate_mcache_row_bytes call. If num_mcaches or
mvmpg_width/height is zero, return a false. Callers will propagate the
failure as a rejected mode, which prevents the panic.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/5302
Reviewed-by: Sun peng (Leo) Li <sunpeng.li@amd.com>
Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
George Zhang
2026-07-16 17:00:01 -04:00
committed by Alex Deucher
parent 040f7925de
commit 29c0f7c655
1 changed files with 25 additions and 6 deletions
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31
drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_core/dml2_core_dcn4_calcs.c
View File

@@ -2453,7 +2453,7 @@ static void calculate_mcache_row_bytes(
DML_ASSERT(*p->num_mcaches > 0);
}
static void calculate_mcache_setting(
static bool calculate_mcache_setting(
struct dml2_core_internal_scratch *scratch,
struct dml2_core_calcs_calculate_mcache_setting_params *p)
{
@@ -2479,7 +2479,7 @@ static void calculate_mcache_setting(
*p->lc_comb_mcache = 0;
if (!p->dcc_enable)
return;
return true;
l->is_dual_plane = dml_is_420(p->source_format) || p->source_format == dml2_rgbe_alpha;
@@ -2516,7 +2516,14 @@ static void calculate_mcache_setting(
l->l_p.mvmpg_per_mcache_lb = &l->mvmpg_per_mcache_lb_l;
calculate_mcache_row_bytes(scratch, &l->l_p);
DML_ASSERT(*p->num_mcaches_l > 0);
if (*p->num_mcaches_l == 0 ||
(p->surf_vert ? l->mvmpg_height_l : l->mvmpg_width_l) == 0) {
DML_LOG_VERBOSE("DML::%s: degenerate luma viewport (num_mcaches_l=%u mvmpg_%s_l=%u) — mode not supported\n",
__func__, *p->num_mcaches_l,
p->surf_vert ? "height" : "width",
p->surf_vert ? l->mvmpg_height_l : l->mvmpg_width_l);
return false;
}
if (l->is_dual_plane) {
l->c_p.num_chans = p->num_chans;
@@ -2552,7 +2559,14 @@ static void calculate_mcache_setting(
l->c_p.mvmpg_per_mcache_lb = &l->mvmpg_per_mcache_lb_c;
calculate_mcache_row_bytes(scratch, &l->c_p);
DML_ASSERT(*p->num_mcaches_c > 0);
if (*p->num_mcaches_c == 0 ||
(p->surf_vert ? l->mvmpg_height_c : l->mvmpg_width_c) == 0) {
DML_LOG_VERBOSE("DML::%s: degenerate chroma viewport (num_mcaches_c=%u mvmpg_%s_c=%u) — mode not supported\n",
__func__, *p->num_mcaches_c,
p->surf_vert ? "height" : "width",
p->surf_vert ? l->mvmpg_height_c : l->mvmpg_width_c);
return false;
}
}
// Sharing for iMALL access
@@ -2662,6 +2676,7 @@ static void calculate_mcache_setting(
*p->mcache_shift_granularity_l = l->mvmpg_access_width_l;
*p->mcache_shift_granularity_c = l->mvmpg_access_width_c;
return true;
}
static void calculate_mall_bw_overhead_factor(
@@ -9490,7 +9505,10 @@ static bool dml_core_mode_support(struct dml2_core_calcs_mode_support_ex *in_out
calculate_mcache_setting_params->mall_comb_mcache_c = &mode_lib->ms.mall_comb_mcache_c[k];
calculate_mcache_setting_params->lc_comb_mcache = &mode_lib->ms.lc_comb_mcache[k];
calculate_mcache_setting(&mode_lib->scratch, calculate_mcache_setting_params);
if (!calculate_mcache_setting(&mode_lib->scratch, calculate_mcache_setting_params)) {
mode_lib->ms.support.ModeSupport = false;
return false;
}
}
calculate_mall_bw_overhead_factor(
@@ -10969,7 +10987,8 @@ static bool dml_core_mode_programming(struct dml2_core_calcs_mode_programming_ex
calculate_mcache_setting_params->mall_comb_mcache_l = &mode_lib->mp.mall_comb_mcache_l[k];
calculate_mcache_setting_params->mall_comb_mcache_c = &mode_lib->mp.mall_comb_mcache_c[k];
calculate_mcache_setting_params->lc_comb_mcache = &mode_lib->mp.lc_comb_mcache[k];
calculate_mcache_setting(&mode_lib->scratch, calculate_mcache_setting_params);
if (!calculate_mcache_setting(&mode_lib->scratch, calculate_mcache_setting_params))
return false;
}
calculate_mall_bw_overhead_factor(