Re: [PATCH] drm/amdgpu/display: fix FP handling in DCN30

["Kazlauskas, Nicholas" <nicholas.kazlauskas@amd.com>]

On 2020-11-12 5:06 p.m., Bhawanpreet Lakha wrote:
> From: Alex Deucher <alexander.deucher@amd.com>
> 
> Adjust the FP handling to avoid nested calls.
> 
> The nested calls cause the warning below
> WARNING: CPU: 3 PID: 384 at arch/x86/kernel/fpu/core.c:129 kernel_fpu_begin
> 
> Fixes: 26803606c5d6 ("drm/amdgpu/display: FP fixes for DCN3.x (v4)")
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>

I guess dropping the noinline is fine if we're just calling it via the 
function pointer.

Regards,
Nicholas Kazlauskas

> ---
>   .../drm/amd/display/dc/dcn30/dcn30_resource.c | 43 +++----------------
>   1 file changed, 6 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_resource.c b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_resource.c
> index b379057e669c..d5c81ad55045 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_resource.c
> @@ -1470,20 +1470,8 @@ int dcn30_populate_dml_pipes_from_context(
>   	return pipe_cnt;
>   }
>   
> -/*
> - * This must be noinline to ensure anything that deals with FP registers
> - * is contained within this call; previously our compiling with hard-float
> - * would result in fp instructions being emitted outside of the boundaries
> - * of the DC_FP_START/END macros, which makes sense as the compiler has no
> - * idea about what is wrapped and what is not
> - *
> - * This is largely just a workaround to avoid breakage introduced with 5.6,
> - * ideally all fp-using code should be moved into its own file, only that
> - * should be compiled with hard-float, and all code exported from there
> - * should be strictly wrapped with DC_FP_START/END
> - */
> -static noinline void dcn30_populate_dml_writeback_from_context_fp(
> -		struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
> +void dcn30_populate_dml_writeback_from_context(
> +	struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
>   {
>   	int pipe_cnt, i, j;
>   	double max_calc_writeback_dispclk;
> @@ -1571,14 +1559,6 @@ static noinline void dcn30_populate_dml_writeback_from_context_fp(
>   
>   }
>   
> -void dcn30_populate_dml_writeback_from_context(
> -		struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes)
> -{
> -	DC_FP_START();
> -	dcn30_populate_dml_writeback_from_context_fp(dc, res_ctx, pipes);
> -	DC_FP_END();
> -}
> -
>   unsigned int dcn30_calc_max_scaled_time(
>   		unsigned int time_per_pixel,
>   		enum mmhubbub_wbif_mode mode,
> @@ -1977,7 +1957,7 @@ static struct pipe_ctx *dcn30_find_split_pipe(
>   	return pipe;
>   }
>   
> -static bool dcn30_internal_validate_bw(
> +static noinline bool dcn30_internal_validate_bw(
>   		struct dc *dc,
>   		struct dc_state *context,
>   		display_e2e_pipe_params_st *pipes,
> @@ -1999,6 +1979,7 @@ static bool dcn30_internal_validate_bw(
>   
>   	pipe_cnt = dc->res_pool->funcs->populate_dml_pipes(dc, context, pipes, fast_validate);
>   
> +	DC_FP_START();
>   	if (!pipe_cnt) {
>   		out = true;
>   		goto validate_out;
> @@ -2222,6 +2203,7 @@ static bool dcn30_internal_validate_bw(
>   	out = false;
>   
>   validate_out:
> +	DC_FP_END();
>   	return out;
>   }
>   
> @@ -2404,7 +2386,7 @@ void dcn30_calculate_wm_and_dlg(
>   	DC_FP_END();
>   }
>   
> -static noinline bool dcn30_validate_bandwidth_fp(struct dc *dc,
> +bool dcn30_validate_bandwidth(struct dc *dc,
>   		struct dc_state *context,
>   		bool fast_validate)
>   {
> @@ -2455,19 +2437,6 @@ static noinline bool dcn30_validate_bandwidth_fp(struct dc *dc,
>   	return out;
>   }
>   
> -bool dcn30_validate_bandwidth(struct dc *dc,
> -		struct dc_state *context,
> -		bool fast_validate)
> -{
> -	bool out;
> -
> -	DC_FP_START();
> -	out = dcn30_validate_bandwidth_fp(dc, context, fast_validate);
> -	DC_FP_END();
> -
> -	return out;
> -}
> -
>   static noinline void get_optimal_dcfclk_fclk_for_uclk(unsigned int uclk_mts,
>                                                          unsigned int *optimal_dcfclk,
>                                                          unsigned int *optimal_fclk)
> 

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