[PATCH 6.18 238/333] drm/amd/display: Fallback to boot snapshot for dispclk

Greg Kroah-Hartman
2026-03-17T17:22:20Z

From: Dillon Varone <Dillon.Varone@amd.com>

commit 30d937f63bd19bbcaafa4b892eb251f8bbbf04ef upstream.

[WHY & HOW]
If the dentist is unavailable, fallback to reading CLKIP via the boot
snapshot to get the current dispclk.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 2ab77600d1e55a042c02437326d3c7563e853c6c)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c
@@ -68,7 +68,11 @@ void dcn401_initialize_min_clocks(struct
* audio corruption. Read current DISPCLK from DENTIST and request the same
* freq to ensure that the timing is valid and unchanged.
*/
- clocks->dispclk_khz = dc->clk_mgr->funcs->get_dispclk_from_dentist(dc->clk_mgr);
+ if (dc->clk_mgr->funcs->get_dispclk_from_dentist) {
+ clocks->dispclk_khz = dc->clk_mgr->funcs->get_dispclk_from_dentist(dc->clk_mgr);
+ } else {
+ clocks->dispclk_khz = dc->clk_mgr->boot_snapshot.dispclk * 1000;
+ }
}
clocks->ref_dtbclk_khz = dc->clk_mgr->bw_params->clk_table.entries[0].dtbclk_mhz * 1000;
clocks->fclk_p_state_change_support = true;