linux-kernel - [PATCH] video: fbdev: fix use of 'dma_map

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Message-ID: <1614571509-40078-1-git-send-email-tanghui20@huawei.com>
Date:   Mon, 1 Mar 2021 12:05:09 +0800
From:   Hui Tang <tanghui20@...wei.com>
To:     <daniel.vetter@...ll.ch>, <grandmaster@...klimov.de>,
        <dri-devel@...ts.freedesktop.org>
CC:     <linux-fbdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] video: fbdev: fix use of 'dma_map_single'

DMA_TO_DEVICE synchronisation must be done after the last modification
of the memory region by the software and before it is handed off to
the device.

Signed-off-by: Hui Tang <tanghui20@...wei.com>
---
 drivers/video/fbdev/grvga.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/grvga.c b/drivers/video/fbdev/grvga.c
index 24818b2..25ae9ef 100644
--- a/drivers/video/fbdev/grvga.c
+++ b/drivers/video/fbdev/grvga.c
@@ -435,6 +435,8 @@ static int grvga_probe(struct platform_device *dev)
 			retval = -ENOMEM;
 			goto dealloc_cmap;
 		}
+
+		memset((unsigned long *) virtual_start, 0, grvga_mem_size);
 	} else {	/* Allocate frambuffer memory */
 
 		unsigned long page;
@@ -449,6 +451,7 @@ static int grvga_probe(struct platform_device *dev)
 			goto dealloc_cmap;
 		}
 
+		memset((unsigned long *) virtual_start, 0, grvga_mem_size);
 		physical_start = dma_map_single(&dev->dev, (void *)virtual_start, grvga_mem_size, DMA_TO_DEVICE);
 
 		/* Set page reserved so that mmap will work. This is necessary
@@ -463,8 +466,6 @@ static int grvga_probe(struct platform_device *dev)
 		par->fb_alloced = 1;
 	}
 
-	memset((unsigned long *) virtual_start, 0, grvga_mem_size);
-
 	info->screen_base = (char __iomem *) virtual_start;
 	info->fix.smem_start = physical_start;
 	info->fix.smem_len   = grvga_mem_size;
-- 
2.8.1