Re: [PATCH v4 1/6] remoteproc: qcom: fix sparse warnings for __iomem annotated mem_region

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

On 4/30/26 9:12 PM, Mukesh Ojha wrote:
> The firmware memory regions in qcom_adsp, qcom_pas and qcom_wcnss are
> mapped using devm_ioremap_wc() / devm_ioremap_resource_wc(), which
> return void __iomem *. However, the mem_region (and dtb_mem_region)
> fields in the respective driver structs were declared as plain void *,
> causing sparse to flag address space mismatches:
> 
> qcom_q6v5_adsp.c:639:26: warning: incorrect type in assignment (different address spaces)
> qcom_q6v5_adsp.c:639:26:    expected void *mem_region
> qcom_q6v5_adsp.c:639:26:    got void [noderef] __iomem *
> qcom_q6v5_pas.c:141:45: warning: incorrect type in argument 2 (different address spaces)
> qcom_q6v5_pas.c:141:45:    expected void const volatile [noderef] __iomem *src
> qcom_q6v5_pas.c:141:45:    got void *
> qcom_q6v5_pas.c:637:25: warning: incorrect type in assignment (different address spaces)
> qcom_q6v5_pas.c:637:25:    expected void *mem_region
> qcom_q6v5_pas.c:637:25:    got void [noderef] __iomem *
> qcom_q6v5_pas.c:654:29: warning: incorrect type in assignment (different address spaces)
> qcom_q6v5_pas.c:654:29:    expected void *dtb_mem_region
> qcom_q6v5_pas.c:654:29:    got void [noderef] __iomem *
> qcom_wcnss.c:540:27: warning: incorrect type in assignment (different address spaces)
> qcom_wcnss.c:540:27:    expected void *mem_region
> qcom_wcnss.c:540:27:    got void [noderef] __iomem *
> 
> Fix this by annotating the struct fields with __iomem to correctly
> reflect the address space of the underlying mapping.
> 
> These regions are subsequently passed to qcom_mdt_load(),
> qcom_mdt_load_no_init() and qcom_mdt_pas_load(), all of which take
> void * and use plain memcpy()/memset() internally to write firmware
> segments into the region. This is intentional and safe: the mappings
> are write-combining (WC), which on arm64 permits bulk CPU stores
> without requiring the memcpy_toio()/memset_io() accessors. Changing
> the MDT loader API to accept void __iomem * would be a more invasive
> change and would affect callers.

Zooming out a bit more, should we even be ioremapping these regions
in the first place? Are they not just RAM/Normal Memory in arm parlance?

Would switching to devm_memremap(, MEMREMAP_WC) (like we do in RMTFS
today) be an even better solution here?

Konrad