| Message ID | 20170627150310.719212-2-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Arnd, On 27.06.2017 18:02, Arnd Bergmann wrote: > In venus_boot(), we pass a pointer to a phys_addr_t > into dmam_alloc_coherent, which the compiler warns about: > > platform/qcom/venus/firmware.c: In function 'venus_boot': > platform/qcom/venus/firmware.c:63:49: error: passing argument 3 of 'dmam_alloc_coherent' from incompatible pointer type [-Werror=incompatible-pointer-types] > > The returned DMA address is later passed on to a function that > takes a phys_addr_t, so it's clearly wrong to use the DMA > mapping interface here: the memory may be uncached, or the > address may be completely wrong if there is an IOMMU connected > to the device. > > My interpretation is that using dmam_alloc_coherent() had two > purposes: > > a) get a chunk of consecutive memory that may be larger than > the limit for kmalloc() > > b) use the devres infrastructure to simplify the unwinding > in the error case. The intension here is to use per-device memory which is removed from kernel allocator, that memory is used by remote processor (Venus) for its code section and system memory, the memory must not be mapped to kernel to avoid any cache issues. As the memory in subject is reserved per-device memory the only legal way to allocate it is by dmam_alloc_coherent() -> dma_alloc_from_coherent(). For me the confusion comes from phys_addr_t which is passed to qcom_mdt_load() and then the address passed to qcom_scm_pas_mem_setup() which probably protects that physical memory. And the tz really expects physical address. The only solution I see is by casting dma_addr_t to phys_addr_t. Yes it is ugly but what is proper solution then? > > I think ideally we'd use a devres-based version of > alloc_pages_exact() here, but since that doesn't exist, > let's use devm_get_free_pages() instead. This wastes a little > memory as the size gets rounded up to a power of two, but > is otherwise harmless. If we want to save memory here, calling > devm_free_pages() to release the memory once it is no longer > needed is probably better anyway. > > Fixes: af2c3834c8ca ("[media] media: venus: adding core part and helper functions") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > The same problem exists in the drm driver, as of commit 7c65817e6d38 > ("drm/msm: gpu: Enable zap shader for A5XX"), and I submitted the > same patch for that already. > --- > drivers/media/platform/qcom/venus/firmware.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/media/platform/qcom/venus/firmware.c b/drivers/media/platform/qcom/venus/firmware.c > index 1b1a4f355918..76edb9f60311 100644 > --- a/drivers/media/platform/qcom/venus/firmware.c > +++ b/drivers/media/platform/qcom/venus/firmware.c > @@ -60,11 +60,13 @@ int venus_boot(struct device *parent, struct device *fw_dev, const char *fwname) > > mem_size = VENUS_FW_MEM_SIZE; > > - mem_va = dmam_alloc_coherent(fw_dev, mem_size, &mem_phys, GFP_KERNEL); > + mem_va = (void *)devm_get_free_pages(parent, GFP_KERNEL, > + get_order(mem_size)); > if (!mem_va) { > ret = -ENOMEM; > goto err_unreg_device; > } > + mem_phys = virt_to_phys(mem_va); > > ret = request_firmware(&mdt, fwname, fw_dev); > if (ret < 0) > regards, Stan
On Tue, Jun 27, 2017 at 9:39 PM, Stanimir Varbanov <stanimir.varbanov@linaro.org> wrote: > Hi Arnd, > > On 27.06.2017 18:02, Arnd Bergmann wrote: >> >> In venus_boot(), we pass a pointer to a phys_addr_t >> into dmam_alloc_coherent, which the compiler warns about: >> >> platform/qcom/venus/firmware.c: In function 'venus_boot': >> platform/qcom/venus/firmware.c:63:49: error: passing argument 3 of >> 'dmam_alloc_coherent' from incompatible pointer type >> [-Werror=incompatible-pointer-types] >> >> The returned DMA address is later passed on to a function that >> takes a phys_addr_t, so it's clearly wrong to use the DMA >> mapping interface here: the memory may be uncached, or the >> address may be completely wrong if there is an IOMMU connected >> to the device. >> >> My interpretation is that using dmam_alloc_coherent() had two >> purposes: >> >> a) get a chunk of consecutive memory that may be larger than >> the limit for kmalloc() >> >> b) use the devres infrastructure to simplify the unwinding >> in the error case. > > > The intension here is to use per-device memory which is removed from kernel > allocator, that memory is used by remote processor (Venus) for its code > section and system memory, the memory must not be mapped to kernel to avoid > any cache issues. > > As the memory in subject is reserved per-device memory the only legal way to > allocate it is by dmam_alloc_coherent() -> dma_alloc_from_coherent(). > > For me the confusion comes from phys_addr_t which is passed to > qcom_mdt_load() and then the address passed to qcom_scm_pas_mem_setup() > which probably protects that physical memory. And the tz really expects > physical address. > > The only solution I see is by casting dma_addr_t to phys_addr_t. Yes it is > ugly but what is proper solution then? If you actually have a separate remote processor that accesses this memory, then qcom_mdt_load() is the wrong interface, as it takes a physical address, and we need to introduce another interface that can take a DMA address relative to a particular device. You cannot cast between the two types because phys_addr_t is an address as seen from the CPU, and dma_addr_t is seen by a particular device, and can only be used together with that device pointer. It looks like the pointer gets passed down to qcom_scm_call(dev, QCOM_SCM_SVC_PIL, QCOM_SCM_PAS_MEM_SETUP_CMD, ...), which in turn takes a 32-bit address, suggesting that this is indeed a dma address for that device (possibly going through an IOMMU), so maybe it just needs to all be changed to dma_addr_t. Is there any official documentation for qcom_scm_call() that clarifies what address space the arguments are in? Arnd
diff --git a/drivers/media/platform/qcom/venus/firmware.c b/drivers/media/platform/qcom/venus/firmware.c index 1b1a4f355918..76edb9f60311 100644 --- a/drivers/media/platform/qcom/venus/firmware.c +++ b/drivers/media/platform/qcom/venus/firmware.c @@ -60,11 +60,13 @@ int venus_boot(struct device *parent, struct device *fw_dev, const char *fwname) mem_size = VENUS_FW_MEM_SIZE; - mem_va = dmam_alloc_coherent(fw_dev, mem_size, &mem_phys, GFP_KERNEL); + mem_va = (void *)devm_get_free_pages(parent, GFP_KERNEL, + get_order(mem_size)); if (!mem_va) { ret = -ENOMEM; goto err_unreg_device; } + mem_phys = virt_to_phys(mem_va); ret = request_firmware(&mdt, fwname, fw_dev); if (ret < 0)
In venus_boot(), we pass a pointer to a phys_addr_t into dmam_alloc_coherent, which the compiler warns about: platform/qcom/venus/firmware.c: In function 'venus_boot': platform/qcom/venus/firmware.c:63:49: error: passing argument 3 of 'dmam_alloc_coherent' from incompatible pointer type [-Werror=incompatible-pointer-types] The returned DMA address is later passed on to a function that takes a phys_addr_t, so it's clearly wrong to use the DMA mapping interface here: the memory may be uncached, or the address may be completely wrong if there is an IOMMU connected to the device. My interpretation is that using dmam_alloc_coherent() had two purposes: a) get a chunk of consecutive memory that may be larger than the limit for kmalloc() b) use the devres infrastructure to simplify the unwinding in the error case. I think ideally we'd use a devres-based version of alloc_pages_exact() here, but since that doesn't exist, let's use devm_get_free_pages() instead. This wastes a little memory as the size gets rounded up to a power of two, but is otherwise harmless. If we want to save memory here, calling devm_free_pages() to release the memory once it is no longer needed is probably better anyway. Fixes: af2c3834c8ca ("[media] media: venus: adding core part and helper functions") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- The same problem exists in the drm driver, as of commit 7c65817e6d38 ("drm/msm: gpu: Enable zap shader for A5XX"), and I submitted the same patch for that already. --- drivers/media/platform/qcom/venus/firmware.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)