Re: [PATCH v2] drm/loongson: stop to set get_vblank_timestamp for LS7A1000 CRTC

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 21.03.26 um 10:29 schrieb Icenowy Zheng:
> 在 2026-03-21六的 17:28 +0800，Icenowy Zheng写道：
>> As there's no known hardware capability about querying vblank on the
>> LS7A1000 display controller, setting get_vblank_timestamp will
>> mislead the
>> kernel about the support of DC-backed high precision vblank query.
>>
>> Drop this function pointer in the CRTC function table for LS7A1000.
>>
>> This solves a kernel warning when booting Linux 7.0-rc3 on a
>> Loongson-3A4000+LS7A1000 Haier Boyue G51 laptop (with injected EDID
>> for
>> replicating the display timing set by the firmware).
>>
>> Signed-off-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>
> Oh forgot to attach when crafting v2:
>
> ```
> Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
> ```

I just want to add that the a-b was given wrt. the correctness of the 
source-code changes.  But now it seems that the hardware does support 
the vblank timestamp, (?) so removing the callback might not be the best 
thing.

Best regards
Thomas

>
>> ---
>> Changes in v2:
>> - Re-formatted Loongson product model numbers per request from
>> Huacai.
>>
>>   drivers/gpu/drm/loongson/lsdc_crtc.c | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/loongson/lsdc_crtc.c
>> b/drivers/gpu/drm/loongson/lsdc_crtc.c
>> index 587fbe285e9ef..b3af8e0cdb15f 100644
>> --- a/drivers/gpu/drm/loongson/lsdc_crtc.c
>> +++ b/drivers/gpu/drm/loongson/lsdc_crtc.c
>> @@ -721,7 +721,6 @@ static const struct drm_crtc_funcs
>> ls7a1000_crtc_funcs = {
>>   	.late_register = lsdc_crtc_late_register,
>>   	.enable_vblank = lsdc_crtc_enable_vblank,
>>   	.disable_vblank = lsdc_crtc_disable_vblank,
>> -	.get_vblank_timestamp =
>> drm_crtc_vblank_helper_get_vblank_timestamp,
>>   	.atomic_print_state = lsdc_crtc_atomic_print_state,
>>   };
>>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)