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

[Mikita Lipski]

On 20/11/2019 05:17, Ville Syrjälä wrote:
> On Tue, Nov 19, 2019 at 04:11:43PM -0500, Mikita Lipski wrote:
>>
>>
>> On 19/11/2019 16:09, Mikita Lipski wrote:
>>>
>>>
>>> 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.
>>>>
>>
>>
>> Sorry made a type below. Supposed to be "I don't think it is broken"
> 
> I mean that it's broken if it actually needs u64 when it's
> currently using unsigned long. So u64 is either overkill or the
> code is currently broken.
> 

None of the calculations exceed u32, so u64 would be an overkill, since 
none of the variables in the structure exceed 16 bits. Therefore u32 is 
enough.

>>
>>> 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 at amd.com>
>>>>> Sent: November 19, 2019 10:08 AM
>>>>> To: Ville Syrjälä <ville.syrjala at linux.intel.com>; Lipski, Mikita
>>>>> <Mikita.Lipski at amd.com>
>>>>> Cc: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org;
>>>>> Cornij, Nikola <Nikola.Cornij at 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 at amd.com wrote:
>>>>>>> From: Mikita Lipski <mikita.lipski at 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 at amd.com>
>>>>>>> Cc: Harry Wentland <harry.wentland at amd.com>
>>>>>>> Signed-off-by: Mikita Lipski <mikita.lipski at 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 at lists.freedesktop.org
>>>>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>>>>
>>>>>
>>>>> -- 
>>>>> Thanks,
>>>>> Mikita Lipski
>>>>> Software Engineer 2, AMD
>>>>> mikita.lipski at amd.com
>>>>
>>>
>>
>> -- 
>> Thanks,
>> Mikita Lipski
>> Software Engineer 2, AMD
>> mikita.lipski at amd.com
> 

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