From: Fangzhi Zuo Date: Tue, 25 Nov 2025 14:51:31 +0000 (-0500) Subject: drm/amd/display: Prevent Gating DTBCLK before It Is Properly Latched X-Git-Tag: v6.12.60~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=53ca559992e6837643ca12ff33c2eea9af225ad9;p=thirdparty%2Fkernel%2Fstable.git drm/amd/display: Prevent Gating DTBCLK before It Is Properly Latched [ Upstream commit cfa0904a35fd0231f4d05da0190f0a22ed881cce ] [why] 1. With allow_0_dtb_clk enabled, the time required to latch DTBCLK to 600 MHz depends on the SMU. If DTBCLK is not latched to 600 MHz before set_mode completes, gating DTBCLK causes the DP2 sink to lose its clock source. 2. The existing DTBCLK gating sequence ungates DTBCLK based on both pix_clk and ref_dtbclk, but gates DTBCLK when either pix_clk or ref_dtbclk is zero. pix_clk can be zero outside the set_mode sequence before DTBCLK is properly latched, which can lead to DTBCLK being gated by mistake. [how] Consider both pixel_clk and ref_dtbclk when determining when it is safe to gate DTBCLK; this is more accurate. Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4701 Fixes: 5949e7c4890c ("drm/amd/display: Enable Dynamic DTBCLK Switch") Reviewed-by: Charlene Liu Reviewed-by: Aurabindo Pillai Signed-off-by: Fangzhi Zuo Signed-off-by: Roman Li Tested-by: Dan Wheeler Signed-off-by: Alex Deucher (cherry picked from commit d04eb0c402780ca037b62a6aecf23b863545ebca) Cc: stable@vger.kernel.org Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn35/dcn35_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn35/dcn35_clk_mgr.c index 3114b3fae9ef..6e9d6090b10f 100644 --- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn35/dcn35_clk_mgr.c +++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn35/dcn35_clk_mgr.c @@ -377,6 +377,8 @@ void dcn35_update_clocks(struct clk_mgr *clk_mgr_base, display_count = dcn35_get_active_display_cnt_wa(dc, context, &all_active_disps); if (new_clocks->dtbclk_en && !new_clocks->ref_dtbclk_khz) new_clocks->ref_dtbclk_khz = 600000; + else if (!new_clocks->dtbclk_en && new_clocks->ref_dtbclk_khz > 590000) + new_clocks->ref_dtbclk_khz = 0; /* * if it is safe to lower, but we are already in the lower state, we don't have to do anything @@ -418,7 +420,7 @@ void dcn35_update_clocks(struct clk_mgr *clk_mgr_base, actual_dtbclk = REG_READ(CLK1_CLK4_CURRENT_CNT); - if (actual_dtbclk) { + if (actual_dtbclk > 590000) { clk_mgr_base->clks.ref_dtbclk_khz = new_clocks->ref_dtbclk_khz; clk_mgr_base->clks.dtbclk_en = new_clocks->dtbclk_en; } diff --git a/drivers/gpu/drm/amd/display/dc/dccg/dcn35/dcn35_dccg.c b/drivers/gpu/drm/amd/display/dc/dccg/dcn35/dcn35_dccg.c index a841eaafbaaa..57202ef3fd98 100644 --- a/drivers/gpu/drm/amd/display/dc/dccg/dcn35/dcn35_dccg.c +++ b/drivers/gpu/drm/amd/display/dc/dccg/dcn35/dcn35_dccg.c @@ -1405,7 +1405,7 @@ static void dccg35_set_dtbclk_dto( __func__, params->otg_inst, params->pixclk_khz, params->ref_dtbclk_khz, req_dtbclk_khz, phase, modulo); - } else { + } else if (!params->ref_dtbclk_khz && !req_dtbclk_khz) { switch (params->otg_inst) { case 0: REG_UPDATE(DCCG_GATE_DISABLE_CNTL5, DTBCLK_P0_GATE_DISABLE, 0);