Commit e3c58708 authored by Jyri Sarha's avatar Jyri Sarha Committed by Greg Kroah-Hartman

drm/tilcdc: Precalculate total frametime in tilcdc_crtc_set_mode()

commit ce99f720 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: default avatarKevin Hao <>
Fixes: 11abbc9f ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
Signed-off-by: default avatarJyri Sarha <>
Reviewed-by: default avatarTomi Valkeinen <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent a5851fdb
......@@ -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)
uint tilcdc_mode_hvtotal(const struct drm_display_mode *mode)
return (uint) div_u64(1000llu * mode->htotal * mode->vtotal,
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)
crtc->hwmode = crtc->state->adjusted_mode;
tilcdc_crtc->hvtotal_us =
static void tilcdc_crtc_enable(struct drm_crtc *crtc)
......@@ -648,7 +659,7 @@ 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);
tdiff = ktime_to_us(ktime_sub(next_vblank, ktime_get()));
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