Re: [PATCH] drm/msm/mdp5: fix 64-bit division in bandwidth calculation

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 22/06/2021 11:03, Dmitry Baryshkov wrote:
> Fix undefined symbols errors arising from 64-bit division on 32-bit
> arm targets. Add 64-bit version of mult_frac and use it for calculating
> bandwidth.
> 
> ERROR: modpost: "__aeabi_ldivmod" [drivers/gpu/drm/msm/msm.ko] undefined!
> ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/msm/msm.ko] undefined!
> 
> Fixes: 7e0230fd096c ("drm/msm/mdp5: provide dynamic bandwidth management")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

We are reworking now bandwidth management for mdp5, so both the original 
patch and the fix can be ignored for now.

> ---
>   drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c  |  2 +-
>   drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c   |  5 ++++-
>   drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c |  2 +-
>   include/linux/math.h                       | 13 +++++++++++++
>   4 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> index a9332078aa13..52724d0a6fea 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> @@ -755,7 +755,7 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
>   	hw_cfg = mdp5_cfg_get_hw_config(mdp5_kms->cfg);
>   
>   	if (hw_cfg->perf.ab_inefficiency)
> -		crtc_bw = mult_frac(crtc_bw, hw_cfg->perf.ab_inefficiency, 100);
> +		crtc_bw = mult_frac_ull(crtc_bw, hw_cfg->perf.ab_inefficiency, 100);
>   	mdp5_cstate->new_crtc_bw = crtc_bw;
>   
>   	/*
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> index 3e1b28d3e41b..85b7093a1218 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> @@ -301,6 +301,7 @@ static const struct mdp_kms_funcs kms_funcs = {
>   void mdp5_kms_set_bandwidth(struct mdp5_kms *mdp5_kms)
>   {
>   	int i;
> +	u64 bw;
>   	u32 full_bw = 0;
>   	struct drm_crtc *tmp_crtc;
>   
> @@ -311,7 +312,9 @@ void mdp5_kms_set_bandwidth(struct mdp5_kms *mdp5_kms)
>   		if (!tmp_crtc->enabled)
>   			continue;
>   
> -		full_bw += Bps_to_icc(to_mdp5_crtc_state(tmp_crtc->state)->new_crtc_bw / mdp5_kms->num_paths);
> +		bw = to_mdp5_crtc_state(tmp_crtc->state)->new_crtc_bw;
> +		do_div(bw, mdp5_kms->num_paths * 1000); /* Bps_to_icc */
> +		full_bw += bw;
>   	}
>   
>   	DBG("SET BW to %d\n", full_bw);
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> index 85275665558b..2ede34177a90 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> @@ -191,7 +191,7 @@ static void mdp5_plane_calc_bw(struct drm_plane_state *state, struct drm_crtc_st
>   		prefill_div = vbp + vpw + vfp;
>   #endif
>   
> -	pstate->plane_bw = max(plane_bw, mult_frac(plane_bw, hw_latency_lines, prefill_div));
> +	pstate->plane_bw = max(plane_bw, mult_frac_ull(plane_bw, hw_latency_lines, prefill_div));
>   }
>   
>   static int mdp5_plane_atomic_check_with_state(struct drm_crtc_state *crtc_state,
> diff --git a/include/linux/math.h b/include/linux/math.h
> index 53674a327e39..1327385905df 100644
> --- a/include/linux/math.h
> +++ b/include/linux/math.h
> @@ -118,6 +118,19 @@
>   }							\
>   )
>   
> +#define mult_frac_ull(x, numer, denom)(			\
> +{							\
> +	typeof(x) quot = (x);				\
> +	typeof(x) rem;					\
> +	do_div(quot, (denom));				\
> +	rem = (x) - quot * (denom);			\
> +	rem = (rem * (numer));				\
> +	do_div(rem, (denom));				\
> +	(quot * (numer)) + rem;				\
> +}							\
> +)
> +
> +
>   #define sector_div(a, b) do_div(a, b)
>   
>   /**
> 


-- 
With best wishes
Dmitry