Re: [PATCH] drm/ast: Treat AST2600 like AST2500 in most places

[Jocelyn Falempe <jfalempe@redhat.com>]

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=bcc77411e8a65929655cef7b63a36000724cdc4b> (patch 
> <https://cgit.freedesktop.org/drm/drm/patch/?id=bcc77411e8a65929655cef7b63a36000724cdc4b>)
> 


So basically this commit should be enough to fix the white lines  and 
flickering with VGA output on AST2600 ?
I will try to have it tested, and if it's good, we may want to have it 
on stable kernel.

Best regards,

-- 

Jocelyn