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@windriver.com Fixes: 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled") Cc: stable@vger.kernel.org # v4.11+ Signed-off-by: Jyri Sarha jsarha@ti.com Reviewed-by: Tomi Valkeinen tomi.valkeinen@ti.com --- This is the final version that is going to be in my tilcdc v4.15 pull request.

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 704db24..6ef4d1a 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_get(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) @@ -642,7 +653,7 @@ 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)