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

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Message-ID: <9a12e042-487b-4937-a583-709f0c37ab12@oss.qualcomm.com>
Date: Wed, 9 Apr 2025 17:40:18 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Connor Abbott <cwabbott0@...il.com>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Konrad Dybcio <konradybcio@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>, Kees Cook <kees@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-hardening@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 3/4] drm/msm/a6xx: Get HBB dynamically, if available

On 4/9/25 5:30 PM, Connor Abbott wrote:
> On Wed, Apr 9, 2025 at 11:22 AM Konrad Dybcio
> <konrad.dybcio@....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@...nel.org> wrote:
>>>>
>>>> From: Konrad Dybcio <konrad.dybcio@....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@....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;
+
        gpu->ubwc_config.rgb565_predicator = 0;
        gpu->ubwc_config.uavflagprd_inv = 0;
        gpu->ubwc_config.min_acc_len = 0;
@@ -636,7 +638,6 @@ static void a6xx_calc_ubwc_config(struct adreno_gpu *gpu)
            adreno_is_a690(gpu) ||
            adreno_is_a730(gpu) ||
            adreno_is_a740_family(gpu)) {
-               /* TODO: get ddr type from bootloader and use 2 for LPDDR4 */
                gpu->ubwc_config.highest_bank_bit = 16;
                gpu->ubwc_config.amsbc = 1;
                gpu->ubwc_config.rgb565_predicator = 1;
@@ -665,6 +666,13 @@ static void a6xx_calc_ubwc_config(struct adreno_gpu *gpu)
                gpu->ubwc_config.highest_bank_bit = 14;
                gpu->ubwc_config.min_acc_len = 1;
        }
+
+       /* Attempt to retrieve HBB data from SMEM, keep the above defaults in case of error */
+       hbb = qcom_smem_dram_get_hbb();
+       if (hbb < 0)
+               return;
+
+       gpu->ubwc_config.highest_bank_bit = hbb;
 }
 
 static void a6xx_set_ubwc_config(struct msm_gpu *gpu)


Konrad