[PATCH] DRM: armada: fix corruption while loading cursors

[Russell King]

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.

Cc: <stable at vger.kernel.org> # 3.13
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
David,

Could you take this patch - it's also a good idea that it's back ported
to stable kernels as it affects all releases which this driver has been
in.  I don't see the need for a pull request as this is just a single
patch.

Thanks.

 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 19ffd5c22944..357e5eb59e89 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;
-- 
1.8.3.1