linux-kernel - [PATCH AUTOSEL 5.4 119/330] drm/amd/display: fix workaround for incorrect double buffer register for DLG ADL and TTU

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Message-Id: <20200918020110.2063155-119-sashal@kernel.org>
Date:   Thu, 17 Sep 2020 21:57:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Tony Cheng <tony.cheng@....com>,
        Yongqiang Sun <yongqiang.sun@....com>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.4 119/330] drm/amd/display: fix workaround for incorrect double buffer register for DLG ADL and TTU

From: Tony Cheng <tony.cheng@....com>

[ Upstream commit 85e148fb963d27152a14e6d399a47aed9bc99c15 ]

[Why]
these registers should have been double buffered. SW workaround we will have SW program the more aggressive (lower) values
whenever we are upating this register, so we will not have underflow at expense of less optimzal request pattern.

[How]
there is a driver bug where we don't check for 0, which is uninitialzed HW default.  since 0 is smaller than any value we need to program,
driver end up with not programming these registers

Signed-off-by: Tony Cheng <tony.cheng@....com>
Reviewed-by: Yongqiang Sun <yongqiang.sun@....com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../gpu/drm/amd/display/dc/dcn21/dcn21_hubp.c | 35 +++++++++++++------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hubp.c b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hubp.c
index a00af513aa2b0..c8f77bd0ce8a6 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hubp.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hubp.c
@@ -73,32 +73,47 @@ void apply_DEDCN21_142_wa_for_hostvm_deadline(
 		struct _vcs_dpi_display_dlg_regs_st *dlg_attr)
 {
 	struct dcn21_hubp *hubp21 = TO_DCN21_HUBP(hubp);
-	uint32_t cur_value;
+	uint32_t refcyc_per_vm_group_vblank;
+	uint32_t refcyc_per_vm_req_vblank;
+	uint32_t refcyc_per_vm_group_flip;
+	uint32_t refcyc_per_vm_req_flip;
+	const uint32_t uninitialized_hw_default = 0;
 
-	REG_GET(VBLANK_PARAMETERS_5, REFCYC_PER_VM_GROUP_VBLANK, &cur_value);
-	if (cur_value > dlg_attr->refcyc_per_vm_group_vblank)
+	REG_GET(VBLANK_PARAMETERS_5,
+			REFCYC_PER_VM_GROUP_VBLANK, &refcyc_per_vm_group_vblank);
+
+	if (refcyc_per_vm_group_vblank == uninitialized_hw_default ||
+			refcyc_per_vm_group_vblank > dlg_attr->refcyc_per_vm_group_vblank)
 		REG_SET(VBLANK_PARAMETERS_5, 0,
 				REFCYC_PER_VM_GROUP_VBLANK, dlg_attr->refcyc_per_vm_group_vblank);
 
 	REG_GET(VBLANK_PARAMETERS_6,
-			REFCYC_PER_VM_REQ_VBLANK,
-			&cur_value);
-	if (cur_value > dlg_attr->refcyc_per_vm_req_vblank)
+			REFCYC_PER_VM_REQ_VBLANK, &refcyc_per_vm_req_vblank);
+
+	if (refcyc_per_vm_req_vblank == uninitialized_hw_default ||
+			refcyc_per_vm_req_vblank > dlg_attr->refcyc_per_vm_req_vblank)
 		REG_SET(VBLANK_PARAMETERS_6, 0,
 				REFCYC_PER_VM_REQ_VBLANK, dlg_attr->refcyc_per_vm_req_vblank);
 
-	REG_GET(FLIP_PARAMETERS_3, REFCYC_PER_VM_GROUP_FLIP, &cur_value);
-	if (cur_value > dlg_attr->refcyc_per_vm_group_flip)
+	REG_GET(FLIP_PARAMETERS_3,
+			REFCYC_PER_VM_GROUP_FLIP, &refcyc_per_vm_group_flip);
+
+	if (refcyc_per_vm_group_flip == uninitialized_hw_default ||
+			refcyc_per_vm_group_flip > dlg_attr->refcyc_per_vm_group_flip)
 		REG_SET(FLIP_PARAMETERS_3, 0,
 				REFCYC_PER_VM_GROUP_FLIP, dlg_attr->refcyc_per_vm_group_flip);
 
-	REG_GET(FLIP_PARAMETERS_4, REFCYC_PER_VM_REQ_FLIP, &cur_value);
-	if (cur_value > dlg_attr->refcyc_per_vm_req_flip)
+	REG_GET(FLIP_PARAMETERS_4,
+			REFCYC_PER_VM_REQ_FLIP, &refcyc_per_vm_req_flip);
+
+	if (refcyc_per_vm_req_flip == uninitialized_hw_default ||
+			refcyc_per_vm_req_flip > dlg_attr->refcyc_per_vm_req_flip)
 		REG_SET(FLIP_PARAMETERS_4, 0,
 					REFCYC_PER_VM_REQ_FLIP, dlg_attr->refcyc_per_vm_req_flip);
 
 	REG_SET(FLIP_PARAMETERS_5, 0,
 			REFCYC_PER_PTE_GROUP_FLIP_C, dlg_attr->refcyc_per_pte_group_flip_c);
+
 	REG_SET(FLIP_PARAMETERS_6, 0,
 			REFCYC_PER_META_CHUNK_FLIP_C, dlg_attr->refcyc_per_meta_chunk_flip_c);
 }
-- 
2.25.1