linux-kernel - [PATCH] amdgpu: Avoid sleeping during FPU critical sections

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Date:   Fri,  8 Jan 2021 16:58:38 -0500
From:   Jeremy Cline <jcline@...hat.com>
To:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jeremy Cline <jcline@...hat.com>,
        Timothy Pearson <tpearson@...torengineering.com>
Subject: [PATCH] amdgpu: Avoid sleeping during FPU critical sections

dcn20_resource_construct() includes a number of kzalloc(GFP_KERNEL)
calls which can sleep, but kernel_fpu_begin() disables preemption and
sleeping in this context is invalid.

The only places the FPU appears to be required is in the
init_soc_bounding_box() function and when calculating the
{min,max}_fill_clk_mhz. Narrow the scope to just these two parts to
avoid sleeping while using the FPU.

Fixes: 7a8a3430be15 ("amdgpu: Wrap FPU dependent functions in dc20")
Cc: Timothy Pearson <tpearson@...torengineering.com>
Signed-off-by: Jeremy Cline <jcline@...hat.com>
---
 drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
index e04ecf0fc0db..a4fa5bf016c1 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
@@ -3622,6 +3622,7 @@ static bool init_soc_bounding_box(struct dc *dc,
 	if (bb && ASICREV_IS_NAVI12_P(dc->ctx->asic_id.hw_internal_rev)) {
 		int i;
 
+		DC_FP_START();
 		dcn2_0_nv12_soc.sr_exit_time_us =
 				fixed16_to_double_to_cpu(bb->sr_exit_time_us);
 		dcn2_0_nv12_soc.sr_enter_plus_exit_time_us =
@@ -3721,6 +3722,7 @@ static bool init_soc_bounding_box(struct dc *dc,
 			dcn2_0_nv12_soc.clock_limits[i].dram_speed_mts =
 					fixed16_to_double_to_cpu(bb->clock_limits[i].dram_speed_mts);
 		}
+		DC_FP_END();
 	}
 
 	if (pool->base.pp_smu) {
@@ -3777,8 +3779,6 @@ static bool dcn20_resource_construct(
 	enum dml_project dml_project_version =
 			get_dml_project_version(ctx->asic_id.hw_internal_rev);
 
-	DC_FP_START();
-
 	ctx->dc_bios->regs = &bios_regs;
 	pool->base.funcs = &dcn20_res_pool_funcs;
 
@@ -3959,8 +3959,10 @@ static bool dcn20_resource_construct(
 				ranges.reader_wm_sets[i].wm_inst = i;
 				ranges.reader_wm_sets[i].min_drain_clk_mhz = PP_SMU_WM_SET_RANGE_CLK_UNCONSTRAINED_MIN;
 				ranges.reader_wm_sets[i].max_drain_clk_mhz = PP_SMU_WM_SET_RANGE_CLK_UNCONSTRAINED_MAX;
+				DC_FP_START();
 				ranges.reader_wm_sets[i].min_fill_clk_mhz = (i > 0) ? (loaded_bb->clock_limits[i - 1].dram_speed_mts / 16) + 1 : 0;
 				ranges.reader_wm_sets[i].max_fill_clk_mhz = loaded_bb->clock_limits[i].dram_speed_mts / 16;
+				DC_FP_END();
 
 				ranges.num_reader_wm_sets = i + 1;
 			}
@@ -4125,12 +4127,10 @@ static bool dcn20_resource_construct(
 		pool->base.oem_device = NULL;
 	}
 
-	DC_FP_END();
 	return true;
 
 create_fail:
 
-	DC_FP_END();
 	dcn20_resource_destruct(pool);
 
 	return false;
-- 
2.28.0