Re: [PATCH] drm/dsc: Return unsigned long on compute offset

[Mikita Lipski <mlipski-5C7GfCeVMHo@public.gmane.org>]

On 19/11/2019 12:11, Ville Syrjälä wrote:
> On Tue, Nov 19, 2019 at 04:59:40PM +0000, Cornij, Nikola wrote:
>> If you're going to make all of them the same, then u64, please.
>>
>> This is because I'm not sure if calculations require 64-bit at some stage.
> 
> If it does then it's already broken. Someone should probably figure out
> what's actally needed instead of shooting ducks with an icbm.
> 
I don't think it is not broken, cause I'm currently testing DSC.
The patch I sent early simply fixes the error of comparing  signed and 
unsigned variables.

We can then submit a second patch addressing the issue of using unsigned 
long int instead of u32. Also, since the variables in drm_dsc_config 
structure are all of type u8 and u16, the calculation values shouldn't 
exceed the size of u32.

Thanks

>>
>> -----Original Message-----
>> From: Lipski, Mikita <Mikita.Lipski@amd.com>
>> Sent: November 19, 2019 10:08 AM
>> To: Ville Syrjälä <ville.syrjala@linux.intel.com>; Lipski, Mikita <Mikita.Lipski@amd.com>
>> Cc: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; Cornij, Nikola <Nikola.Cornij@amd.com>
>> Subject: Re: [PATCH] drm/dsc: Return unsigned long on compute offset
>>
>>
>>
>> On 19/11/2019 09:56, Ville Syrjälä wrote:
>>> On Tue, Nov 19, 2019 at 09:45:26AM -0500, mikita.lipski@amd.com wrote:
>>>> From: Mikita Lipski <mikita.lipski@amd.com>
>>>>
>>>> We shouldn't compare int with unsigned long to find the max value and
>>>> since we are not expecting negative value returned from
>>>> compute_offset we should make this function return unsigned long so
>>>> we can compare the values when computing rc parameters.
>>>
>>> Why are there other unsigned longs in dsc parameter computation in the
>>> first place?
>>
>> I believe it was initially set to be unsigned long for variable consistency, when we ported intel_compute_rc_parameters into drm_dsc_compute_rc_parameters. But now that I look at it, we can actually just set them to u32 or u64, as nothing should exceed that.
>>>
>>>>
>>>> Cc: Nikola Cornij <nikola.cornij@amd.com>
>>>> Cc: Harry Wentland <harry.wentland@amd.com>
>>>> Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
>>>> ---
>>>>    drivers/gpu/drm/drm_dsc.c | 6 +++---
>>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_dsc.c b/drivers/gpu/drm/drm_dsc.c
>>>> index 74f3527f567d..ec40604ab6a2 100644
>>>> --- a/drivers/gpu/drm/drm_dsc.c
>>>> +++ b/drivers/gpu/drm/drm_dsc.c
>>>> @@ -245,11 +245,11 @@ void drm_dsc_pps_payload_pack(struct drm_dsc_picture_parameter_set *pps_payload,
>>>>    }
>>>>    EXPORT_SYMBOL(drm_dsc_pps_payload_pack);
>>>>    
>>>> -static int compute_offset(struct drm_dsc_config *vdsc_cfg, int pixels_per_group,
>>>> +static unsigned long compute_offset(struct drm_dsc_config *vdsc_cfg, int pixels_per_group,
>>>>    				int groups_per_line, int grpcnt)
>>>>    {
>>>> -	int offset = 0;
>>>> -	int grpcnt_id = DIV_ROUND_UP(vdsc_cfg->initial_xmit_delay, pixels_per_group);
>>>> +	unsigned long offset = 0;
>>>> +	unsigned long grpcnt_id = DIV_ROUND_UP(vdsc_cfg->initial_xmit_delay, pixels_per_group);
>>>>    
>>>>    	if (grpcnt <= grpcnt_id)
>>>>    		offset = DIV_ROUND_UP(grpcnt * pixels_per_group * vdsc_cfg->bits_per_pixel, 16);
>>>> -- 
>>>> 2.17.1
>>>>
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel@lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>
>> -- 
>> Thanks,
>> Mikita Lipski
>> Software Engineer 2, AMD
>> mikita.lipski@amd.com
> 

-- 
Thanks,
Mikita Lipski
Software Engineer 2, AMD
mikita.lipski@amd.com
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