Hi Jocelyn Falempe,
-----Original Message----- From: Jocelyn Falempe [mailto:jfalempe@redhat.com] Sent: Wednesday, June 08, 2022 9:17 PM To: Kuo-Hsiang Chou kuohsiang_chou@aspeedtech.com; Thomas Zimmermann tzimmermann@suse.de; airlied@redhat.com; airlied@linux.ie; daniel@ffwll.ch; regressions@leemhuis.info Cc: dri-devel@lists.freedesktop.org; stable@vger.kernel.org; Luke Chen luke_chen@aspeedtech.com; Hungju Huang hungju_huang@aspeedtech.com; Charles Kuan charles_kuan@aspeedtech.com Subject: Re: [PATCH] drm/ast: Treat AST2600 like AST2500 in most places
On 08/06/2022 10:09, Kuo-Hsiang Chou wrote:
Hi Thomas
Thanks for your suggestions!
I answer each revision inline that followed by [KH]:.
Thanks for reviewing this.
Regards,
Kuo-Hsiang Chou
-----Original Message-----
From: Thomas Zimmermann [mailto:tzimmermann@suse.de]
Sent: Tuesday, June 07, 2022 8:03 PM
To: airlied@redhat.com; airlied@linux.ie; daniel@ffwll.ch; jfalempe@redhat.com; regressions@leemhuis.info; Kuo-Hsiang Chou kuohsiang_chou@aspeedtech.com
Subject: [PATCH] drm/ast: Treat AST2600 like AST2500 in most places
Include AST2600 in most of the branches for AST2500. Thereby revert most effects of commit f9bd00e0ea9d ("drm/ast: Create chip AST2600").
The AST2600 used to be treated like an AST2500, which at least gave usable display output. After introducing AST2600 in the driver without further updates, lots of functions take the wrong branches.
Handling AST2600 in the AST2500 branches reverts back to the original settings. The exception are cases where AST2600 meanwhile got its own branch.
[KH]: Based on CVE_2019_6260 item3, P2A is disallowed anymore.
P2A (PCIe to AMBA) is a bridge that is able to revise any BMC registers.
Yes, P2A is dangerous on security issue, because Host open a backdoor and someone malicious SW/APP will be easy to take control of BMC.
Therefore, P2A is disabled forever.
Now, return to this patch, there is no need to add AST2600 condition on the P2A flow.
[snip]
[KH]: Yes, the patch is "drm/ast: Create threshold values for AST2600" that is the root cause of whites lines on AST2600
commit
bcc77411e8a65929655cef7b63a36000724cdc4b https://cgit.freedesktop.org/drm/drm/commit/?id=bcc77411e8a65929655ce f7b63a36000724cdc4b (patch https://cgit.freedesktop.org/drm/drm/patch/?id=bcc77411e8a65929655cef 7b63a36000724cdc4b)
So basically this commit should be enough to fix the white lines and flickering with VGA output on AST2600 ? [KH]: Yes. You are welcome to tell me something if you consider there is other strange issue. Thanks for your efforts on drm/ast project! Regards, Kuo-Hsiang Chou
I will try to have it tested, and if it's good, we may want to have it on stable kernel.
Best regards,