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    Subject[PATCH 5.10 087/290] drm/amd/display: Fix nested FPU context in dcn21_validate_bandwidth()
    Date
    From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    From: Holger Hoffstätte <holger@applied-asynchrony.com>

    commit 15e8b95d5f7509e0b09289be8c422c459c9f0412 upstream.

    Commit 41401ac67791 added FPU wrappers to dcn21_validate_bandwidth(),
    which was correct. Unfortunately a nested function alredy contained
    DC_FP_START()/DC_FP_END() calls, which results in nested FPU context
    enter/exit and complaints by kernel_fpu_begin_mask().
    This can be observed e.g. with 5.10.20, which backported 41401ac67791
    and now emits the following warning on boot:

    WARNING: CPU: 6 PID: 858 at arch/x86/kernel/fpu/core.c:129 kernel_fpu_begin_mask+0xa5/0xc0
    Call Trace:
    dcn21_calculate_wm+0x47/0xa90 [amdgpu]
    dcn21_validate_bandwidth_fp+0x15d/0x2b0 [amdgpu]
    dcn21_validate_bandwidth+0x29/0x40 [amdgpu]
    dc_validate_global_state+0x3c7/0x4c0 [amdgpu]

    The warning is emitted due to the additional DC_FP_START/END calls in
    patch_bounding_box(), which is inlined into dcn21_calculate_wm(),
    its only caller. Removing the calls brings the code in line with
    dcn20 and makes the warning disappear.

    Fixes: 41401ac67791 ("drm/amd/display: Add FPU wrappers to dcn21_validate_bandwidth()")
    Signed-off-by: Holger Hoffstätte <holger@applied-asynchrony.com>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c | 4 ----
    1 file changed, 4 deletions(-)

    --- a/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
    +++ b/drivers/gpu/drm/amd/display/dc/dcn21/dcn21_resource.c
    @@ -1058,8 +1058,6 @@ static void patch_bounding_box(struct dc
    {
    int i;

    - DC_FP_START();
    -
    if (dc->bb_overrides.sr_exit_time_ns) {
    for (i = 0; i < WM_SET_COUNT; i++) {
    dc->clk_mgr->bw_params->wm_table.entries[i].sr_exit_time_us =
    @@ -1084,8 +1082,6 @@ static void patch_bounding_box(struct dc
    dc->bb_overrides.dram_clock_change_latency_ns / 1000.0;
    }
    }
    -
    - DC_FP_END();
    }

    void dcn21_calculate_wm(

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