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

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commit 298360af3d 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.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Russell Currey
2016-12-15 16:12:41 +11:00
committed by Greg Kroah-Hartman
parent 8dbd6f709e
commit 66469319c0
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);
}