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@xxxxxxxxxxxxx>
Fixes: 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
Signed-off-by: Jyri Sarha <jsarha@xxxxxx>
---
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;
+
+ if (totalframes < U32_MAX / 1000u)
+ return (1000u * totalframes) / mode->clock;
+ else
+ return 10u * ((100u * totalframes) / mode->clock);
+}
+
static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
{
struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
@@ -459,6 +470,9 @@ static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
drm_framebuffer_get(fb);
crtc->hwmode = crtc->state->adjusted_mode;
+
+ tilcdc_crtc->frametime_us =
+ tilcdc_mode_frametime(&crtc->hwmode);
}
static void tilcdc_crtc_enable(struct drm_crtc *crtc)
@@ -642,7 +656,7 @@ 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->frametime_us);
tdiff = ktime_to_us(ktime_sub(next_vblank, ktime_get()));
if (tdiff < TILCDC_VBLANK_SAFETY_THRESHOLD_US)
--
1.9.1
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