Re: [PATCH v3 0/3] Retrieve information about DDR from SMEM

[Neil Armstrong <neil.armstrong@linaro.org>]

On 1/8/26 15:21, Konrad Dybcio wrote:
> SMEM allows the OS to retrieve information about the DDR memory.
> Among that information, is a semi-magic value called 'HBB', or Highest
> Bank address Bit, which multimedia drivers (for hardware like Adreno
> and MDSS) must retrieve in order to program the IP blocks correctly.
> 
> This series introduces an API to retrieve that value, uses it in the
> aforementioned programming sequences and exposes available DDR
> frequencies in debugfs (to e.g. pass to aoss_qmp debugfs). More
> information can be exposed in the future, as needed.
> 
> Patch 3 should really be merged after 1&2
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> ---
> Changes in v3:
> - Support v6 and v7 DDRInfo (v7 is used on e.g. Hamoa)
> - Handle rare cases of DDRInfo v5 with additional trailing data
> - Rebase/adjust to SSoT UBWC
> - Expose hbb value in debugfs
> - cosmetic changes
> - Link to v2: https://lore.kernel.org/r/20250410-topic-smem_dramc-v2-0-dead15264714@oss.qualcomm.com
> 
> Changes in v2:
> - Avoid checking for < 0 on unsigned types
> - Overwrite Adreno UBWC data to keep the data shared with userspace
>    coherent with what's programmed into the hardware
> - Call get_hbb() in msm_mdss_enable() instead of all UBWC setup
>    branches separately
> - Pick up Bjorn's rb on patch 1
> - Link to v1: https://lore.kernel.org/r/20250409-topic-smem_dramc-v1-0-94d505cd5593@oss.qualcomm.com
> 
> ---
> Konrad Dybcio (3):
>        soc: qcom: smem: Expose DDR data from SMEM
>        soc: qcom: ubwc: Get HBB from SMEM
>        drm/msm/adreno: Trust the SSoT UBWC config
> 
>   drivers/gpu/drm/msm/adreno/a5xx_gpu.c   |  11 +-
>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c   |  82 +------
>   drivers/gpu/drm/msm/adreno/adreno_gpu.h |   5 -
>   drivers/soc/qcom/Makefile               |   3 +-
>   drivers/soc/qcom/smem.c                 |  14 +-
>   drivers/soc/qcom/smem.h                 |   9 +
>   drivers/soc/qcom/smem_dramc.c           | 408 ++++++++++++++++++++++++++++++++
>   drivers/soc/qcom/ubwc_config.c          |  69 ++++--
>   include/linux/soc/qcom/smem.h           |   4 +
>   9 files changed, 485 insertions(+), 120 deletions(-)
> ---
> base-commit: fc4e91c639c0af93d63c3d5bc0ee45515dd7504a
> change-id: 20250409-topic-smem_dramc-6467187ac865
> 
> Best regards,

Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8650-HDK

root@qemuarm64:~# cat /sys/kernel/debug/qcom_smem/
dram_frequencies  hbb
root@qemuarm64:~# cat /sys/kernel/debug/qcom_smem/dram_frequencies
200000000
547200000
768000000
1555200000
1708800000
2092800000
2736000000
3187200000
3686400000
4224000000
root@qemuarm64:~# cat /sys/kernel/debug/qcom_smem/hbb
16

Thanks,
Neil