Message-ID: <26953463-dae1-0f07-9e4e-0314ee8ea81a@quicinc.com>
Date:   Wed, 1 Mar 2023 02:14:59 +0530
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Subject: Re: [PATCH v3 04/15] drm/msm/a6xx: Extend and explain UBWC config
Content-Language: en-US
To:     Konrad Dybcio <konrad.dybcio@linaro.org>,
        Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>
CC:     <linux-arm-msm@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
        <freedreno@lists.freedesktop.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Rob Clark <robdclark@chromium.org>
References: <20230223-topic-gmuwrapper-v3-0-5be55a336819@linaro.org>
 <20230223-topic-gmuwrapper-v3-4-5be55a336819@linaro.org>
 <e19b5cd7-9125-a285-accc-ecf530804cfc@quicinc.com>
 <487a6890-4b8f-d541-e074-5d3ab7424678@linaro.org>
From:   Akhil P Oommen <quic_akhilpo@quicinc.com>
In-Reply-To: <487a6890-4b8f-d541-e074-5d3ab7424678@linaro.org>
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Precedence: bulk

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.
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.

-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)
>>>