[PATCH] drm/tilcdc: Precalculate total frametime in tilcdc_crtc_set_mode()

[Tomi Valkeinen]


Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

On 12/10/17 17:16, Jyri Sarha wrote:
> We need the frame refresh time to check if we are too close to
> vertical sync when updating the two framebuffer DMA registers and risk
> a collision. This new method is more accurate that the previous that
> based on mode's vrefresh value, which itself may also be inaccurate
> or not even initialized.
> 
> Reported-by: Kevin Hao <kexin.hao at windriver.com>
> Fixes: 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
> Cc: <stable at vger.kernel.org> # v4.11+
> Signed-off-by: Jyri Sarha <jsarha at ti.com>
> ---
> This patch is inteded to replace this:
> https://lists.freedesktop.org/archives/dri-devel/2017-October/154556.html
> 
>  drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index 704db24..b2f2170 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -48,6 +48,7 @@ struct tilcdc_crtc {
>  	unsigned int lcd_fck_rate;
>  
>  	ktime_t last_vblank;
> +	unsigned int frametime_us;
>  
>  	struct drm_framebuffer *curr_fb;
>  	struct drm_framebuffer *next_fb;
> @@ -292,6 +293,16 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
>  				LCDC_V2_CORE_CLK_EN);
>  }
>  
> +u32 tilcdc_mode_frametime(const struct drm_display_mode *mode)
> +{
> +	u32 totalframes = mode->htotal * mode->vtotal;

"totalframes"? Shouldn't it be total pixels (including blanking pixels)?
Or maybe "hvtotal", mimicking the htotal and vtotal.

> +
> +	if (totalframes < U32_MAX / 1000u)
> +		return (1000u * totalframes) / mode->clock;
> +	else
> +		return 10u * ((100u * totalframes) / mode->clock);

Just pick one, I don't think there's benefit in the above if. Perhaps go
via u64 div.

 Tomi