[PATCH 6.6.y] drm/amd/display: Drop clock requirements on DCN32 when no displays are active

[Sasha Levin <sashal@kernel.org>]

From: Misha Nasledov <misha@nasledov.com>

[ Upstream commit bba4dc3306483335ddbe065c05b2d8359ec387a4 ]

amdgpu_dm builds the new dc_state as a copy of the old one. When the last
stream is removed, dml1_validate() returns early on pipe_cnt == 0 and
never reaches dcn32_calculate_dlg_params(), so bw.dcn.clk keeps the
dramclk/dcfclk/fclk requirements of the display that was just turned off.
dcn32_update_clocks() then keeps those hard minimums applied.

On an RX 7900 XTX this leaves UCLK at 456 MHz and DCFCLK at 637 MHz with
the monitor off, and the board idles at 28.4 W. With this change they
drop to 96 MHz and 145 MHz and board power falls to 15.3 W.

Reset the clock requirements in that case, as calculate_dlg_params()
already does when no HUBP is active and as the DML2 path does for
stream_count == 0.

Signed-off-by: Misha Nasledov <misha@nasledov.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 0261a0ef89f37ef962fbc9dbc724ebf65fe681cf)
Cc: stable@vger.kernel.org
[ sashal: Adapted the dml1_validate() change to dcn32_validate_bandwidth() after its existing MALL state restore. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .../gpu/drm/amd/display/dc/dcn32/dcn32_resource.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
index ab6b4f44f537c..f85672062af30 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
@@ -1860,8 +1860,21 @@ bool dcn32_validate_bandwidth(struct dc *dc,
 	if (fast_validate)
 		dcn32_restore_mall_state(dc, context, &mall_temp_config);
 
-	if (pipe_cnt == 0)
+	if (pipe_cnt == 0) {
+		/* The context is a copy of the previous state, so without this the
+		 * clocks the last display needed stay applied with all displays off.
+		 */
+		context->bw_ctx.bw.dcn.clk.socclk_khz = 0;
+		context->bw_ctx.bw.dcn.clk.dppclk_khz = 0;
+		context->bw_ctx.bw.dcn.clk.dcfclk_khz = 0;
+		context->bw_ctx.bw.dcn.clk.dcfclk_deep_sleep_khz = 0;
+		context->bw_ctx.bw.dcn.clk.dramclk_khz = 0;
+		context->bw_ctx.bw.dcn.clk.fclk_khz = 0;
+		context->bw_ctx.bw.dcn.clk.p_state_change_support = true;
+		context->bw_ctx.bw.dcn.clk.fclk_p_state_change_support = true;
+		context->bw_ctx.bw.dcn.clk.num_ways = 0;
 		goto validate_out;
+	}
 
 	if (!out)
 		goto validate_fail;
-- 
2.53.0