[PATCH v3] soc: qcom: ubwc: Fix link error when QCOM_SMEM=n

[PATCH v3] soc: qcom: ubwc: Fix link error when QCOM_SMEM=n

[Daniel Baluta]

DRM_MSM unconditionally selects QCOM_UBWC_CONFIG, which calls SMEM APIs,
causing a link error on non-Qcom platforms (e.g. SOC_IMX5):

  arm-linux-gnueabihf-ld: ubwc_config.c:(.text+0x2c): undefined
      reference to 'qcom_smem_is_available'
  arm-linux-gnueabihf-ld: ubwc_config.c:(.text+0x4c): undefined
      reference to 'qcom_smem_dram_get_hbb'

Make QCOM_UBWC_CONFIG depend on QCOM_SMEM to make the requirement
explicit, and guard the select in DRM_MSM with ARCH_QCOM && QCOM_SMEM so
it is only selected when its dependency is met.

Fixes: 1b445022d1d0 ("soc: qcom: ubwc: Get HBB from SMEM")
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
---
Changes since v2:
 - guard QCOM_UBWC_CONFIG both with ARCH_QCOM and QCOM_SMEM otherwise
we could force QCOM_SMEM=n and still have QCOM_UBWC_CONFIG=m as reported
by Nathan Chancellor
 - Link to v2: https://lore.kernel.org/imx/20260811223622.GA934543@ax162/T/#t

Changes since v1:
- (addressed feedback from Dmitry) replace adding static inline stubs with preparing a better config
  dependecies so that we use the qcom_smem symbols only on QCOM platforms.
- Link to v1: https://lore.kernel.org/imx/sy2ulk536ryakhy6fdnqr4asvzvufqk3dlo2awdrfomulyf4n4@qtp4qoazqmhj/T/#t

 drivers/gpu/drm/msm/Kconfig | 2 +-
 drivers/soc/qcom/Kconfig    | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/Kconfig b/drivers/gpu/drm/msm/Kconfig
index 09469d56513b0..1670dbc9464c6 100644
--- a/drivers/gpu/drm/msm/Kconfig
+++ b/drivers/gpu/drm/msm/Kconfig
@@ -22,7 +22,7 @@ config DRM_MSM
 	select TMPFS
 	select QCOM_SCM
 	select QCOM_PAS
-	select QCOM_UBWC_CONFIG
+	select QCOM_UBWC_CONFIG if ARCH_QCOM && QCOM_SMEM
 	select WANT_DEV_COREDUMP
 	select SND_SOC_HDMI_CODEC if SND_SOC
 	select SYNC_FILE
diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
index fd4d4ecd2df0f..e0629e9328c87 100644
--- a/drivers/soc/qcom/Kconfig
+++ b/drivers/soc/qcom/Kconfig
@@ -321,6 +321,7 @@ config QCOM_QMI_HELPERS
 
 config QCOM_UBWC_CONFIG
 	tristate
+	depends on QCOM_SMEM
 	help
 	  Most Qualcomm SoCs feature a number of Universal Bandwidth Compression
 	  (UBWC) engines across various IP blocks, which need to be initialized
-- 
2.45.2

Re: [PATCH v3] soc: qcom: ubwc: Fix link error when QCOM_SMEM=n

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] The patch adds `depends on QCOM_SMEM` to `QCOM_UBWC_CONFIG` but fails to update `VIDEO_QCOM_IRIS` which unconditionally selects it, leading to a Kconfig unmet dependency warning and a link error when `QCOM_SMEM=n`.
- [High] When `DRM_MSM` is built-in (`y`) and `QCOM_SMEM` is a module (`m`), the new conditional select forces `QCOM_UBWC_CONFIG` to `m`, resulting in undefined references to `qcom_ubwc_config_get_data` during vmlinux linkage.
--

--- Patch [1]: [PATCH v3] soc: qcom: ubwc: Fix link error when QCOM_SMEM=n ---
commit dd72552ce5111faee423365870490e3e7c98c8db
Author: Daniel Baluta <daniel.baluta@nxp.com>

soc: qcom: ubwc: Fix link error when QCOM_SMEM=n

DRM_MSM unconditionally selects QCOM_UBWC_CONFIG, which calls SMEM APIs,
causing a link error on non-Qcom platforms. Make QCOM_UBWC_CONFIG depend
on QCOM_SMEM to make the requirement explicit, and guard the select in
DRM_MSM with ARCH_QCOM && QCOM_SMEM.

Link: https://lore.kernel.org/imx/20260811223622.GA934543@ax162/T/#t
Link: https://lore.kernel.org/imx/sy2ulk536ryakhy6fdnqr4asvzvufqk3dlo2awdrfomulyf4n4@qtp4qoazqmhj/T/#t

> diff --git a/drivers/gpu/drm/msm/Kconfig b/drivers/gpu/drm/msm/Kconfig
> index 09469d56513b0..1670dbc9464c6 100644
> --- a/drivers/gpu/drm/msm/Kconfig
> +++ b/drivers/gpu/drm/msm/Kconfig
[ ... ]
> @@ -22,7 +22,7 @@ config DRM_MSM
>  	select TMPFS
>  	select QCOM_SCM
>  	select QCOM_PAS
> -	select QCOM_UBWC_CONFIG
> +	select QCOM_UBWC_CONFIG if ARCH_QCOM && QCOM_SMEM

[Severity: High]
If DRM_MSM is built-in (=y) and QCOM_SMEM is a module (=m), this conditional
select expression evaluates to 'm'. This leaves QCOM_UBWC_CONFIG configured as
a module (=m) while DRM_MSM is built-in.

Because include/linux/soc/qcom/ubwc.h uses IS_ENABLED(CONFIG_QCOM_UBWC_CONFIG),
which evaluates to true for both built-in and modules:

#if IS_ENABLED(CONFIG_QCOM_UBWC_CONFIG)
const struct qcom_ubwc_cfg_data *qcom_ubwc_config_get_data(void);
#else
static inline const struct qcom_ubwc_cfg_data *qcom_ubwc_config_get_data(void)
...

Doesn't this result in an undefined reference to qcom_ubwc_config_get_data
when linking vmlinux, since the static inline stub is not provided? Should
IS_REACHABLE() be used in the header instead, or should the dependency be
adjusted?

>  	select WANT_DEV_COREDUMP
>  	select SND_SOC_HDMI_CODEC if SND_SOC
>  	select SYNC_FILE
> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> index fd4d4ecd2df0f..e0629e9328c87 100644
> --- a/drivers/soc/qcom/Kconfig
> +++ b/drivers/soc/qcom/Kconfig
[ ... ]
> @@ -321,6 +321,7 @@ config QCOM_QMI_HELPERS
>  
>  config QCOM_UBWC_CONFIG
>  	tristate
> +	depends on QCOM_SMEM

[Severity: High]
By adding this dependency, doesn't this create an unmet dependency for
VIDEO_QCOM_IRIS which also selects QCOM_UBWC_CONFIG?

In drivers/media/platform/qcom/iris/Kconfig:

config VIDEO_QCOM_IRIS
    ...
    select QCOM_UBWC_CONFIG

When a config symbol uses select, it must have dependencies at least as
restrictive as the selected symbol. Since VIDEO_QCOM_IRIS unconditionally
selects QCOM_UBWC_CONFIG, if it is enabled while QCOM_SMEM=n, it bypasses
this new dependency.

Will this cause Kconfig to force QCOM_UBWC_CONFIG to be built, generating
an unmet dependency warning, and failing with the exact same undefined
reference to qcom_smem_is_available that this patch intends to fix?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260812130421.670527-1-daniel.baluta@nxp.com?part=1