From dcf5bd889a7ce3d9e53bd8075fbade59ebae9104 Mon Sep 17 00:00:00 2001 From: Bartosz Golaszewski Date: Mon, 27 May 2024 14:55:03 +0200 Subject: [PATCH] firmware: qcom: scm: clarify the comment in qcom_scm_pas_init_image() The "memory protection" mechanism mentioned in the comment is the SHM Bridge. This is also the reason why we do not convert this call to using the TZ memory allocator. Signed-off-by: Bartosz Golaszewski Tested-by: Andrew Halaney # sc8280xp-lenovo-thinkpad-x13s Tested-by: Deepti Jaggi #sa8775p-ride Reviewed-by: Elliot Berman Link: https://lore.kernel.org/r/20240527-shm-bridge-v10-13-ce7afaa58d3a@linaro.org Signed-off-by: Bjorn Andersson --- drivers/firmware/qcom/qcom_scm.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c index df748fa8af4d..00c379a3cceb 100644 --- a/drivers/firmware/qcom/qcom_scm.c +++ b/drivers/firmware/qcom/qcom_scm.c @@ -582,6 +582,13 @@ int qcom_scm_pas_init_image(u32 peripheral, const void *metadata, size_t size, * During the scm call memory protection will be enabled for the meta * data blob, so make sure it's physically contiguous, 4K aligned and * non-cachable to avoid XPU violations. + * + * For PIL calls the hypervisor creates SHM Bridges for the blob + * buffers on behalf of Linux so we must not do it ourselves hence + * not using the TZMem allocator here. + * + * If we pass a buffer that is already part of an SHM Bridge to this + * call, it will fail. */ mdata_buf = dma_alloc_coherent(__scm->dev, size, &mdata_phys, GFP_KERNEL); -- 2.50.1