[linux-yocto] [PATCH 4.12] drm/tilcdc: Precalculate total frametime in tilcdc_crtc_set_mode()

[Bruce Ashfield]

On 01/18/2018 02:30 PM, Kevin Hao wrote:
> From: Jyri Sarha <jsarha at ti.com>
> 
> commit ce99f7206c9105851d97202ed08c058af6f11ac4 upstream
> 
> We need the total 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 is inaccurate or may not
> even be 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>
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
> ---
> This fixes the Bug 12131 - Kernel traceback when reboot beaglebone black.
>    https://bugzilla.yoctoproject.org/show_bug.cgi?id=12131

Thanks for adding this, it helps when considering the "why" for
a patch.

this is now merged, I'll do SRCREV updates in a bit, once some of
the recent CVE changes have been completed.

Bruce

> 
>   drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index d524ed0d5146..9e607b914c2b 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -24,6 +24,7 @@
>   #include <linux/completion.h>
>   #include <linux/dma-mapping.h>
>   #include <linux/of_graph.h>
> +#include <linux/math64.h>
>   
>   #include "tilcdc_drv.h"
>   #include "tilcdc_regs.h"
> @@ -48,6 +49,7 @@ struct tilcdc_crtc {
>   	unsigned int lcd_fck_rate;
>   
>   	ktime_t last_vblank;
> +	unsigned int hvtotal_us;
>   
>   	struct drm_framebuffer *curr_fb;
>   	struct drm_framebuffer *next_fb;
> @@ -292,6 +294,12 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
>   				LCDC_V2_CORE_CLK_EN);
>   }
>   
> +uint tilcdc_mode_hvtotal(const struct drm_display_mode *mode)
> +{
> +	return (uint) div_u64(1000llu * mode->htotal * mode->vtotal,
> +			      mode->clock);
> +}
> +
>   static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
>   {
>   	struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
> @@ -459,6 +467,9 @@ static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
>   	drm_framebuffer_reference(fb);
>   
>   	crtc->hwmode = crtc->state->adjusted_mode;
> +
> +	tilcdc_crtc->hvtotal_us =
> +		tilcdc_mode_hvtotal(&crtc->hwmode);
>   }
>   
>   static void tilcdc_crtc_enable(struct drm_crtc *crtc)
> @@ -636,7 +647,7 @@ int tilcdc_crtc_update_fb(struct drm_crtc *crtc,
>   		spin_lock_irqsave(&tilcdc_crtc->irq_lock, flags);
>   
>   		next_vblank = ktime_add_us(tilcdc_crtc->last_vblank,
> -					   1000000 / crtc->hwmode.vrefresh);
> +					   tilcdc_crtc->hvtotal_us);
>   		tdiff = ktime_to_us(ktime_sub(next_vblank, ktime_get()));
>   
>   		if (tdiff < TILCDC_VBLANK_SAFETY_THRESHOLD_US)
>