[PATCH 2/2] drivers/gpu/drm/ast: Fix infinite loop if read fails

From: Defang Bo
Date: Fri Dec 25 2020 - 06:38:04 EST


[Why] Similar to commit <298360af3> ast_init_dram_reg() configures a window in order to access BMC memory.
A BMC register can be configured to disallow this, and if so, causes
an infinite loop in the ast driver which renders the system unusable.
[How]
Fix this by erroring out if an error is detected.

Signed-off-by: Defang Bo <bodefang@xxxxxxx>
---
drivers/gpu/drm/ast/ast_post.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_post.c b/drivers/gpu/drm/ast/ast_post.c
index ef19c70..86e4d23 100644
--- a/drivers/gpu/drm/ast/ast_post.c
+++ b/drivers/gpu/drm/ast/ast_post.c
@@ -302,13 +302,13 @@ static void ast_init_dram_reg(struct drm_device *dev)
ast_write32(ast, 0x12000, 0x1688A8A8);
do {
if (pci_channel_offline(dev->pdev))
- return -EIO;
+ return -EIO;
} while (ast_read32(ast, 0x12000) != 0x01);

ast_write32(ast, 0x10000, 0xfc600309);
do {
if (pci_channel_offline(dev->pdev))
- return -EIO;
+ return -EIO;
} while (ast_read32(ast, 0x10000) != 0x01);
}

--
2.7.4