drm/tegra: bad irqsave/restore in tegra_dc_finish_page_flip()

PATCH In review Dan Carpenter 2 participants 2 messages Jan 7, 2015

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DRM drivers Kernel janitors Tegra architecture support DRM drivers for NVIDIA Tegra

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Dan Carpenter

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2015-01-07 11:01 UTC #0 lore raw

PATCH 1/1 drm/tegra: bad irqsave/restore in tegra_dc_finish_page_flip()

We can't save two values to the IRQ flags at the same time so the IRQs are not enabled at the end. This kind of bug is easy to miss in testing if the function is normally called with IRQs disabled so we wouldn't enable IRQs anyway.

Signed-off-by Dan Carpenter <[email protected]>

drivers/gpu/drm/tegra/dc.c +2 -2

index ae26cc0..c746161 100644
@@ -838,7 +838,7 @@ static void tegra_dc_finish_page_flip(struct tegra_dc *dc)
 
 	bo = tegra_fb_get_plane(crtc->primary->fb, 0);
 
-	spin_lock_irqsave(&dc->lock, flags);
+	spin_lock(&dc->lock);
 
 	/* check if new start address has been latched */
 	tegra_dc_writel(dc, WINDOW_A_SELECT, DC_CMD_DISPLAY_WINDOW_HEADER);

@@ -846,7 +846,7 @@ static void tegra_dc_finish_page_flip(struct tegra_dc *dc)
 	base = tegra_dc_readl(dc, DC_WINBUF_START_ADDR);
 	tegra_dc_writel(dc, 0, DC_CMD_STATE_ACCESS);
 
-	spin_unlock_irqrestore(&dc->lock, flags);
+	spin_unlock(&dc->lock);
 
 	if (base = bo->paddr + crtc->primary->fb->offsets[0]) {
 		drm_crtc_send_vblank_event(crtc, dc->event);

Thierry Reding

2015-01-07 13:46 UTC #1 lore raw

Quoted 6 lines · Dan Carpenter

We can't save two values to the IRQ flags at the same time so the IRQs are not enabled at the end. This kind of bug is easy to miss in testing if the function is normally called with IRQs disabled so we wouldn't enable IRQs anyway.
Signed-off-by Dan Carpenter <[email protected]>

Good catch, applied.

Thanks,
Thierry