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

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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: Russell Currey <ruscur@russell.cc>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161215051241.20815-1-ruscur@russell.cc
This commit is contained in:
Russell Currey 2016-12-15 16:12:41 +11:00 committed by Daniel Vetter
parent 2cf026ae85
commit 298360af3d
1 changed files with 5 additions and 2 deletions
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7
drivers/gpu/drm/ast/ast_main.c
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@ -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);
@ -428,7 +429,9 @@ 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);
}