Re: [PATCH] drm/stm: ltdc: use crtc_mode_fixup to update adjusted_mode clock

[Yannick FERTRE <yannick.fertre@st.com>]

On 01/25/2018 05:01 PM, Philippe Cornu wrote:
> There is a difference between the panel/bridge requested pixel clock
> value and the real one due to the hw platform clock preciseness (pll,
> dividers...). This patch updates the adjusted_mode clock value with
> the real hw clock value so then attached encoder & connector can use
> it for precise timing computations.
Reviewed-by: Yannick Fertré <yannick.fertre@st.com>
> Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 35 +++++++++++++++++++++++++----------
>   1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index b48589343ae1..90b3de516c91 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -428,12 +428,35 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
>   	reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR);
>   }
>   
> +static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc,
> +				 const struct drm_display_mode *mode,
> +				 struct drm_display_mode *adjusted_mode)
> +{
> +	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
> +	int rate = mode->clock * 1000;
> +
> +	/*
> +	 * TODO clk_round_rate() does not work yet. When ready, it can
> +	 * be used instead of clk_set_rate() then clk_get_rate().
> +	 */
> +
> +	clk_disable(ldev->pixel_clk);
> +	if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
> +		DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
> +		return false;
> +	}
> +	clk_enable(ldev->pixel_clk);
> +
> +	adjusted_mode->clock = clk_get_rate(ldev->pixel_clk) / 1000;
> +
> +	return true;
> +}
> +
>   static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
>   {
>   	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
>   	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
>   	struct videomode vm;
> -	int rate = mode->clock * 1000;
>   	u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
>   	u32 total_width, total_height;
>   	u32 val;
> @@ -456,15 +479,6 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
>   	total_width = accum_act_w + vm.hfront_porch;
>   	total_height = accum_act_h + vm.vfront_porch;
>   
> -	clk_disable(ldev->pixel_clk);
> -
> -	if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
> -		DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
> -		return;
> -	}
> -
> -	clk_enable(ldev->pixel_clk);
> -
>   	/* Configures the HS, VS, DE and PC polarities. Default Active Low */
>   	val = 0;
>   
> @@ -528,6 +542,7 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc,
>   }
>   
>   static const struct drm_crtc_helper_funcs ltdc_crtc_helper_funcs = {
> +	.mode_fixup = ltdc_crtc_mode_fixup,
>   	.mode_set_nofb = ltdc_crtc_mode_set_nofb,
>   	.atomic_flush = ltdc_crtc_atomic_flush,
>   	.atomic_enable = ltdc_crtc_atomic_enable,