linux-kernel - [PATCH 3.14 101/158] DRM: armada: fix corruption while loading cursors

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Message-Id: <20140504154043.675989489@linuxfoundation.org>
Date:	Sun,  4 May 2014 11:40:10 -0400
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Russell King <rmk+kernel@....linux.org.uk>,
	Dave Airlie <airlied@...hat.com>
Subject: [PATCH 3.14 101/158] DRM: armada: fix corruption while loading cursors

3.14-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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/armada/armada_crtc.c |    1 +
 1 file changed, 1 insertion(+)

--- 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
 				       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;


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