Patch "drivers/gpu/drm/ast: Fix infinite loop if read fails" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

drivers/gpu/drm/ast: Fix infinite loop if read fails

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drivers-gpu-drm-ast-fix-infinite-loop-if-read-fails.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Russell Currey <[email protected]>
Date: Thu, 15 Dec 2016 16:12:41 +1100
Subject: drivers/gpu/drm/ast: Fix infinite loop if read fails

From: Russell Currey <[email protected]>

commit 298360af3dab45659810fdc51aba0c9f4097e4f6 upstream.

ast_get_dram_info() 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.

Fix this by erroring out if an error is detected. On powerpc systems with EEH, this leads to the device being fenced and the system continuing to operate.

---
 drivers/gpu/drm/ast/ast_main.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

@@ -223,7 +223,8 @@ static int ast_get_dram_info(struct drm_
 	ast_write32(ast, 0x10000, 0xfc600309);
 
 	do {
-		;
+		if (pci_channel_offline(dev->pdev))
+			return -EIO;
 	} while (ast_read32(ast, 0x10000) != 0x01);
 	data = ast_read32(ast, 0x10004);
 

@@ -429,7 +430,9 @@ int ast_driver_load(struct drm_device *d
 	ast_detect_chip(dev, &need_post);
 
 	if (ast->chip != AST1180) {
-		ast_get_dram_info(dev);
+		ret = ast_get_dram_info(dev);
+		if (ret)
+			goto out_free;
 		ast->vram_size = ast_get_vram_info(dev);
 		DRM_INFO("dram %d %d %d %08x\n", ast->mclk, ast->dram_type, ast->dram_bus_width, ast->vram_size);
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drivers-gpu-drm-ast-fix-infinite-loop-if-read-fails.patch