linux-kernel - [PATCH 3.13 143/151] DRM: armada: fix corruption while loading cursors

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Message-Id: <1399045139-4531-144-git-send-email-kamal@canonical.com>
Date:	Fri,  2 May 2014 08:38:51 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Russell King <rmk+kernel@....linux.org.uk>,
	Dave Airlie <airlied@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 143/151] DRM: armada: fix corruption while loading cursors

3.13.11.1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Russell King <rmk+kernel@....linux.org.uk>

commit c39b06951f1dc2e384650288676c5b7dcc0ec92c upstream.

Loading cursors to the LCD controller's SRAM can be corrupted when the
configured pixel clock is relatively slow.  This seems to be caused
when we write back-to-back to the SRAM registers.

There doesn't appear to be any status register we can read to check
when an access has completed.

Inserting a dummy read between the writes appears to fix the problem.

Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/gpu/drm/armada/armada_crtc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/armada/armada_crtc.c b/drivers/gpu/drm/armada/armada_crtc.c
index d8e3982..66a492a 100644
--- a/drivers/gpu/drm/armada/armada_crtc.c
+++ b/drivers/gpu/drm/armada/armada_crtc.c
@@ -678,6 +678,7 @@ static void armada_load_cursor_argb(void __iomem *base, uint32_t *pix,
 				       base + LCD_SPU_SRAM_WRDAT);
 			writel_relaxed(addr | SRAM_WRITE,
 				       base + LCD_SPU_SRAM_CTRL);
+			readl_relaxed(base + LCD_SPU_HWC_OVSA_HPXL_VLN);
 			addr += 1;
 			if ((addr & 0x00ff) == 0)
 				addr += 0xf00;
-- 
1.9.1

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