Commit 6fdb4af1 authored by Russell Currey's avatar Russell Currey Committed by Sasha Levin

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

[ Upstream commit 298360af ]

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.

Cc: <stable@vger.kernel.org> # 3.10+
Signed-off-by: default avatarRussell Currey <ruscur@russell.cc>
Reviewed-by: default avatarJoel Stanley <joel@jms.id.au>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161215051241.20815-1-ruscur@russell.ccSigned-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
parent d1b9fb84
......@@ -223,7 +223,8 @@ static int ast_get_dram_info(struct drm_device *dev)
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 *dev, unsigned long flags)
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);
}
......
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