Re: [Freedreno] [PATCH v3 04/15] drm/msm/a6xx: Extend and explain UBWC config

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 28.02.2023 21:48, Akhil P Oommen wrote:
> On 3/1/2023 2:14 AM, Akhil P Oommen wrote:
>> On 3/1/2023 2:10 AM, Konrad Dybcio wrote:
>>> On 28.02.2023 21:23, Akhil P Oommen wrote:
>>>> On 2/23/2023 5:36 PM, Konrad Dybcio wrote:
>>>>> Rename lower_bit to hbb_lo and explain what it signifies.
>>>>> Add explanations (wherever possible to other tunables).
>>>>>
>>>>> Sort the variable definition and assignment alphabetically.
>>>> Sorting based on decreasing order of line length is more readable, isn't it?
>>> I can do that.
>>>
>>>>> Port setting min_access_length, ubwc_mode and hbb_hi from downstream.
>>>>> Set default values for all of the tunables to zero, as they should be.
>>>>>
>>>>> Values were validated against downstream and will be fixed up in
>>>>> separate commits so as not to make this one even more messy.
>>>>>
>>>>> A618 remains untouched (left at hw defaults) in this patch.
>>>>>
>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>>>> ---
>>>>>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 55 ++++++++++++++++++++++++++++-------
>>>>>  1 file changed, 45 insertions(+), 10 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>> index c5f5d0bb3fdc..bdae341e0a7c 100644
>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>> @@ -786,39 +786,74 @@ static void a6xx_set_cp_protect(struct msm_gpu *gpu)
>>>>>  static void a6xx_set_ubwc_config(struct msm_gpu *gpu)
>>>>>  {
>>>>>  	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>>>>> -	u32 lower_bit = 2;
>>>>> +	/* Unknown, introduced with A640/680 */
>>>>>  	u32 amsbc = 0;
>>>>> +	/*
>>>>> +	 * The Highest Bank Bit value represents the bit of the highest DDR bank.
>>>>> +	 * We then subtract 13 from it (13 is the minimum value allowed by hw) and
>>>>> +	 * write the lowest two bits of the remaining value as hbb_lo and the
>>>>> +	 * one above it as hbb_hi to the hardware. The default values (when HBB is
>>>>> +	 * not specified) are 0, 0.
>>>>> +	 */
>>>>> +	u32 hbb_hi = 0;
>>>>> +	u32 hbb_lo = 0;
>>>>> +	/* Whether the minimum access length is 64 bits */
>>>>> +	u32 min_acc_len = 0;
>>>>> +	/* Unknown, introduced with A650 family, related to UBWC mode/ver 4 */
>>>>>  	u32 rgb565_predicator = 0;
>>>>> +	/* Unknown, introduced with A650 family */
>>>>>  	u32 uavflagprd_inv = 0;
>>>>> +	/* Entirely magic, per-GPU-gen value */
>>>>> +	u32 ubwc_mode = 0;
>>>>>  
>>>>>  	/* a618 is using the hw default values */
>>>>>  	if (adreno_is_a618(adreno_gpu))
>>>>>  		return;
>>>>>  
>>>>> -	if (adreno_is_a640_family(adreno_gpu))
>>>>> +	if (adreno_is_a619(adreno_gpu)) {
>>>>> +		/* HBB = 14 */
>>>>> +		hbb_lo = 1;
>>>>> +	}
>>>>> +
>>>>> +	if (adreno_is_a630(adreno_gpu)) {
>>>>> +		/* HBB = 15 */
>>>>> +		hbb_lo = 2;
>>>>> +	}
>>>>> +
>>>>> +	if (adreno_is_a640_family(adreno_gpu)) {
>>>>>  		amsbc = 1;
>>>>> +		/* HBB = 15 */
>>>>> +		hbb_lo = 2;
>>>>> +	}
>>>>>  
>>>>>  	if (adreno_is_a650(adreno_gpu) || adreno_is_a660(adreno_gpu)) {
>>>>> -		/* TODO: get ddr type from bootloader and use 2 for LPDDR4 */
>>>>> -		lower_bit = 3;
>>>>>  		amsbc = 1;
>>>>> +		/* TODO: get ddr type from bootloader and use 2 for LPDDR4 */
>>>>> +		/* HBB = 16 */
>>>>> +		hbb_lo = 3;
>>>>>  		rgb565_predicator = 1;
>>>>>  		uavflagprd_inv = 2;
>>>>>  	}
>>>>>  
>>>>>  	if (adreno_is_7c3(adreno_gpu)) {
>>>>> -		lower_bit = 1;
>>>>>  		amsbc = 1;
>>>>> +		/* HBB is unset in downstream DTS, defaulting to 0 */
>>>> This is incorrect. For 7c3 hbb value is 14. So hbb_lo should be 1. FYI, hbb configurations were moved to the driver from DT in recent downstream kernels.
>>> Right, seems to have happened with msm-5.10. Though a random kernel I
>>> grabbed seems to suggest it's 15 and not 14?
>>>
>>> https://github.com/sonyxperiadev/kernel/blob/aosp/K.P.1.0.r1/drivers/gpu/msm/adreno-gpulist.h#L1710
>> We override that with 14 in a6xx_init() for LP4 platforms dynamically. Since 7c3 is only supported on LP4, we can hardcode 14 here.
Okay, I see.

>> In the downstream kernel, there is an api (of_fdt_get_ddrtype()) to detect ddrtype. If we can get something like that in upstream, we should implement a similar logic here.
Yeah, I mentioned it here [1], but I doubt it'd be implemented,
given what Krzysztof pointed out.

>>
>> -Akhil.
> Also, I haven't closely reviewed other targets configuration you updated, but it is a good idea to leave the existing configurations here as it in this refactor patch. Any update should be a separate patch.
Sure, will do.

Konrad

[1] https://github.com/devicetree-org/devicetree-specification/issues/62
> 
> -Akhil.
>>> Konrad
>>>> -Akhil.
>>>>>  		rgb565_predicator = 1;
>>>>>  		uavflagprd_inv = 2;
>>>>>  	}
>>>>>  
>>>>>  	gpu_write(gpu, REG_A6XX_RB_NC_MODE_CNTL,
>>>>> -		rgb565_predicator << 11 | amsbc << 4 | lower_bit << 1);
>>>>> -	gpu_write(gpu, REG_A6XX_TPL1_NC_MODE_CNTL, lower_bit << 1);
>>>>> -	gpu_write(gpu, REG_A6XX_SP_NC_MODE_CNTL,
>>>>> -		uavflagprd_inv << 4 | lower_bit << 1);
>>>>> -	gpu_write(gpu, REG_A6XX_UCHE_MODE_CNTL, lower_bit << 21);
>>>>> +		  rgb565_predicator << 11 | hbb_hi << 10 | amsbc << 4 |
>>>>> +		  min_acc_len << 3 | hbb_lo << 1 | ubwc_mode);
>>>>> +
>>>>> +	gpu_write(gpu, REG_A6XX_TPL1_NC_MODE_CNTL, hbb_hi << 4 |
>>>>> +		  min_acc_len << 3 | hbb_lo << 1 | ubwc_mode);
>>>>> +
>>>>> +	gpu_write(gpu, REG_A6XX_SP_NC_MODE_CNTL, hbb_hi << 10 |
>>>>> +		  uavflagprd_inv << 4 | min_acc_len << 3 |
>>>>> +		  hbb_lo << 1 | ubwc_mode);
>>>>> +
>>>>> +	gpu_write(gpu, REG_A6XX_UCHE_MODE_CNTL, min_acc_len << 23 | hbb_lo << 21);
>>>>>  }
>>>>>  
>>>>>  static int a6xx_cp_init(struct msm_gpu *gpu)
>>>>>
>