On 01/06/2022 12:33, Thomas Zimmermann wrote:
Hi Jocelyn,
thanks for reporting this bug.
Am 01.06.22 um 11:33 schrieb Jocelyn Falempe:
Hi,
I've found a regression in the ast driver, for AST2600 hardware.
before the upstream commit f9bd00e0ea9d
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f9bd00e0ea9d9b04140aa969a9a13ad3597a1e4e
The ast driver handled AST 2600 chip like an AST 2500.
After this commit, it uses some default values, more like the older
AST chip.
There are a lot of places in the driver like this:
https://elixir.bootlin.com/linux/v5.18.1/source/drivers/gpu/drm/ast/ast_post.c#L82
where it checks for (AST2300 || AST2400 || AST2500) but not for AST2600.
This makes the VGA output, to be blurred and flickered with whites
lines on AST2600.
The issue is present since v5.11
For v5.11~v5.17 I propose a simple workaround (as there are no other
reference to AST2600 in the driver):
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -146,7 +146,8 @@ static int ast_detect_chip(struct drm_device *dev,
bool *need_post)
/* Identify chipset */
if (pdev->revision >= 0x50) {
- ast->chip = AST2600;
+ /* Workaround to use the same codepath for AST2600 */
+ ast->chip = AST2500;
The whole handling of different models in this driver is broken by
design and needs to be replaced. I don't have much of the affected
hardware, so such things are going slowly. :(
For an intermediate fix, it would be better to change all tests for
AST2500 to include AST2600 as well. There aren't too many IIRC.
I feel a bit uncomfortable doing this, because I don't know if this
settings are good for AST2600 or not. I just know that AST2500 settings
are better than the "default".
Also it may not apply cleanly up to v5.11
I will do a test patch and see what it gives.
Another solution would be to just revert f9bd00e0ea9d for v5.11 to v5.17 ?
Best regards,
--
Jocelyn
Best regards
Thomas
drm_info(dev, "AST 2600 detected\n");
} else if (pdev->revision >= 0x40) {
ast->chip = AST2500;
starting from v5.18, there is another reference to AST2600 in the code
https://elixir.bootlin.com/linux/v5.18/source/drivers/gpu/drm/ast/ast_main.c#L212
So I think someone with good aspeed knowledge should review all
locations where there is a test for AST2500, and figure out what
should be done for AST2600
Thanks,
