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Patch "drm/tilcdc: Precalculate total frametime in tilcdc_crtc_set_mode()" has been added to the 4.14-stable tree

PATCH [email protected] 1 participant 1 message Dec 4, 2017

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This is a note to let you know that I've just added the patch titled

drm/tilcdc: Precalculate total frametime in tilcdc_crtc_set_mode()

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-tilcdc-precalculate-total-frametime-in-tilcdc_crtc_set_mode.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From ce99f7206c9105851d97202ed08c058af6f11ac4 Mon Sep 17 00:00:00 2001

From: Jyri Sarha <[email protected]>
Date: Thu, 12 Oct 2017 12:19:46 +0300
Subject: drm/tilcdc: Precalculate total frametime in tilcdc_crtc_set_mode()

From: Jyri Sarha <[email protected]>

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 <[email protected]>
Fixes 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
Signed-off-by Jyri Sarha <[email protected]>
Reviewed-by Tomi Valkeinen <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)
drivers/gpu/drm/tilcdc/tilcdc_crtc.c +12 -1
@@ -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 d
 				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_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)

@@ -648,7 +659,7 @@ int tilcdc_crtc_update_fb(struct drm_crt
 		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)

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/drm-tilcdc-precalculate-total-frametime-in-tilcdc_crtc_set_mode.patch