Re: [PATCH 3/4] drm/msm/a6xx: Get HBB dynamically, if available

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 4/9/25 5:44 PM, Connor Abbott wrote:
> On Wed, Apr 9, 2025 at 11:40 AM Konrad Dybcio
> <konrad.dybcio@oss.qualcomm.com> wrote:
>>
>> On 4/9/25 5:30 PM, Connor Abbott wrote:
>>> On Wed, Apr 9, 2025 at 11:22 AM Konrad Dybcio
>>> <konrad.dybcio@oss.qualcomm.com> wrote:
>>>>
>>>> On 4/9/25 5:12 PM, Connor Abbott wrote:
>>>>> On Wed, Apr 9, 2025 at 10:48 AM Konrad Dybcio <konradybcio@kernel.org> wrote:
>>>>>>
>>>>>> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>>>>>>
>>>>>> The Highest Bank address Bit value can change based on memory type used.
>>>>>>
>>>>>> Attempt to retrieve it dynamically, and fall back to a reasonable
>>>>>> default (the one used prior to this change) on error.
>>>>>>
>>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>>>>>> ---
>>>>>>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 22 ++++++++++++++++------
>>>>>>  1 file changed, 16 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>>> index 06465bc2d0b4b128cddfcfcaf1fe4252632b6777..0cc397378c99db35315209d0265ad9223e8b55c7 100644
>>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>>>>> @@ -13,6 +13,7 @@
>>>>>>  #include <linux/firmware/qcom/qcom_scm.h>
>>>>>>  #include <linux/pm_domain.h>
>>>>>>  #include <linux/soc/qcom/llcc-qcom.h>
>>>>>> +#include <linux/soc/qcom/smem.h>
>>>>>>
>>>>>>  #define GPU_PAS_ID 13
>>>>>>
>>>>>> @@ -669,17 +670,22 @@ static void a6xx_calc_ubwc_config(struct adreno_gpu *gpu)
>>>>>>  static void a6xx_set_ubwc_config(struct msm_gpu *gpu)
>>>>>>  {
>>>>>>         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>>>>>> +       u32 hbb = qcom_smem_dram_get_hbb();
>>>>>> +       u32 ubwc_mode = adreno_gpu->ubwc_config.ubwc_swizzle & 1;
>>>>>> +       u32 level2_swizzling_dis = !(adreno_gpu->ubwc_config.ubwc_swizzle & 2);
>>>>>> +       u32 hbb_hi, hbb_lo;
>>>>>> +
>>>>>>         /*
>>>>>>          * We subtract 13 from the highest bank bit (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.
>>>>>>          */
>>>>>> -       BUG_ON(adreno_gpu->ubwc_config.highest_bank_bit < 13);
>>>>>> -       u32 hbb = adreno_gpu->ubwc_config.highest_bank_bit - 13;
>>>>>> -       u32 hbb_hi = hbb >> 2;
>>>>>> -       u32 hbb_lo = hbb & 3;
>>>>>> -       u32 ubwc_mode = adreno_gpu->ubwc_config.ubwc_swizzle & 1;
>>>>>> -       u32 level2_swizzling_dis = !(adreno_gpu->ubwc_config.ubwc_swizzle & 2);
>>>>>> +       if (hbb < 0)
>>>>>> +               hbb = adreno_gpu->ubwc_config.highest_bank_bit;
>>>>>
>>>>> No. The value we expose to userspace must match what we program.
>>>>> You'll break VK_EXT_host_image_copy otherwise.
>>>>
>>>> I didn't know that was exposed to userspace.
>>>>
>>>> The value must be altered either way - ultimately, the hardware must
>>>> receive the correct information. ubwc_config doesn't seem to be const,
>>>> so I can edit it there if you like it better.
>>>>
>>>> Konrad
>>>
>>> Yes, you should be calling qcom_smem_dram_get_hbb() in
>>> a6xx_calc_ubwc_config(). You can already see there's a TODO there to
>>> plug it in.
>>
>> Does this look good instead?
>>
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> index 0cc397378c99..ae8dbc250e6a 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> @@ -588,6 +588,8 @@ static void a6xx_set_cp_protect(struct msm_gpu *gpu)
>>
>>  static void a6xx_calc_ubwc_config(struct adreno_gpu *gpu)
>>  {
>> +       u8 hbb;
> 
> You can't make it u8 and then test for a negative value on error.

Fair. I think it was u8 in a pre-release version of the patchset and it
stuck in my mind.. though I'dve expected clang to warn me here..

> Other than that, looks good.

Thanks, I'll change it in v2.

Konrad