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.
Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
---
Changes in v4:
- Rebase on top of Dmitry's cleanups to ubwc_config
- Mark and consume the shared data as little-endian
- Fix compiler optimizing out what it thinks is impossible (odd
v3_14freq case)
- Rework qcom_ubwc_config_get_data() per discussion to not alter
hardcoded data
- Remove some unnecessary comments and assignments
- Return -ENODATA instead of -EINVAL for out-of-sensible-range HBB
- Cosmetic/line wrapping fixups
- Drop applied drm/msm patch
- Link to v3: https://lore.kernel.org/r/20260108-topic-smem_dramc-v3-0-6b64df58a017@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
To: Bjorn Andersson <andersson@kernel.org>
To: Konrad Dybcio <konradybcio@kernel.org>
To: Kees Cook <kees@kernel.org>
To: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-hardening@vger.kernel.org
---
Konrad Dybcio (2):
soc: qcom: smem: Expose DDR data from SMEM
soc: qcom: ubwc: Get HBB from SMEM
drivers/soc/qcom/Makefile | 3 +-
drivers/soc/qcom/smem.c | 14 +-
drivers/soc/qcom/smem.h | 9 +
drivers/soc/qcom/smem_dramc.c | 430 +++++++++++++++++++++++++++++++++++++++++
drivers/soc/qcom/ubwc_config.c | 40 +++-
include/linux/soc/qcom/smem.h | 2 +
6 files changed, 495 insertions(+), 3 deletions(-)
---
base-commit: 3fe08b9796f36ef437ab9328e7dd1e5ff2d66603
change-id: 20250409-topic-smem_dramc-6467187ac865
Best regards,
--
Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>