diff options
Diffstat (limited to 'target/linux/generic/pending-4.14/170-usb-dwc2-Fix-DMA-alignment-to-start-at-allocated-boun.patch')
| -rw-r--r-- | target/linux/generic/pending-4.14/170-usb-dwc2-Fix-DMA-alignment-to-start-at-allocated-boun.patch | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/target/linux/generic/pending-4.14/170-usb-dwc2-Fix-DMA-alignment-to-start-at-allocated-boun.patch b/target/linux/generic/pending-4.14/170-usb-dwc2-Fix-DMA-alignment-to-start-at-allocated-boun.patch new file mode 100644 index 0000000..49b33d5 --- /dev/null +++ b/target/linux/generic/pending-4.14/170-usb-dwc2-Fix-DMA-alignment-to-start-at-allocated-boun.patch @@ -0,0 +1,126 @@ +From 028c9191bdf88f120f65626920a6a679170fcc3e Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Antti=20Sepp=C3=A4l=C3=A4?= <a.seppala@gmail.com> +Date: Thu, 5 Jul 2018 11:37:03 +0300 +Subject: [PATCH 1/2] usb: dwc2: Fix DMA alignment to start at allocated + boundary +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +The commit 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more +supported way") introduced a common way to align DMA allocations. +The code in the commit aligns the struct dma_aligned_buffer but the +actual DMA address pointed by data[0] gets aligned to an offset from +the allocated boundary by the kmalloc_ptr and the old_xfer_buffer +pointers. + +This is against the recommendation in Documentation/DMA-API.txt which +states: + + Therefore, it is recommended that driver writers who don't take + special care to determine the cache line size at run time only map + virtual regions that begin and end on page boundaries (which are + guaranteed also to be cache line boundaries). + +The effect of this is that architectures with non-coherent DMA caches +may run into memory corruption or kernel crashes with Unhandled +kernel unaligned accesses exceptions. + +Fix the alignment by positioning the DMA area in front of the allocation +and use memory at the end of the area for storing the orginal +transfer_buffer pointer. This may have the added benefit of increased +performance as the DMA area is now fully aligned on all architectures. + +Tested with Lantiq xRX200 (MIPS) and RPi Model B Rev 2 (ARM). + +Fixes: 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more +supported way") + +Signed-off-by: Antti Seppälä <a.seppala@gmail.com> +--- + drivers/usb/dwc2/hcd.c | 44 +++++++++++++++++++++++--------------------- + 1 file changed, 23 insertions(+), 21 deletions(-) + +--- a/drivers/usb/dwc2/hcd.c ++++ b/drivers/usb/dwc2/hcd.c +@@ -2628,34 +2628,29 @@ static void dwc2_hc_init_xfer(struct dwc + + #define DWC2_USB_DMA_ALIGN 4 + +-struct dma_aligned_buffer { +- void *kmalloc_ptr; +- void *old_xfer_buffer; +- u8 data[0]; +-}; +- + static void dwc2_free_dma_aligned_buffer(struct urb *urb) + { +- struct dma_aligned_buffer *temp; ++ void *stored_xfer_buffer; + + if (!(urb->transfer_flags & URB_ALIGNED_TEMP_BUFFER)) + return; + +- temp = container_of(urb->transfer_buffer, +- struct dma_aligned_buffer, data); ++ /* Restore urb->transfer_buffer from the end of the allocated area */ ++ memcpy(&stored_xfer_buffer, urb->transfer_buffer + ++ urb->transfer_buffer_length, sizeof(urb->transfer_buffer)); + + if (usb_urb_dir_in(urb)) +- memcpy(temp->old_xfer_buffer, temp->data, ++ memcpy(stored_xfer_buffer, urb->transfer_buffer, + urb->transfer_buffer_length); +- urb->transfer_buffer = temp->old_xfer_buffer; +- kfree(temp->kmalloc_ptr); ++ kfree(urb->transfer_buffer); ++ urb->transfer_buffer = stored_xfer_buffer; + + urb->transfer_flags &= ~URB_ALIGNED_TEMP_BUFFER; + } + + static int dwc2_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags) + { +- struct dma_aligned_buffer *temp, *kmalloc_ptr; ++ void *kmalloc_ptr; + size_t kmalloc_size; + + if (urb->num_sgs || urb->sg || +@@ -2663,22 +2658,29 @@ static int dwc2_alloc_dma_aligned_buffer + !((uintptr_t)urb->transfer_buffer & (DWC2_USB_DMA_ALIGN - 1))) + return 0; + +- /* Allocate a buffer with enough padding for alignment */ ++ /* ++ * Allocate a buffer with enough padding for original transfer_buffer ++ * pointer. This allocation is guaranteed to be aligned properly for ++ * DMA ++ */ + kmalloc_size = urb->transfer_buffer_length + +- sizeof(struct dma_aligned_buffer) + DWC2_USB_DMA_ALIGN - 1; ++ sizeof(urb->transfer_buffer); + + kmalloc_ptr = kmalloc(kmalloc_size, mem_flags); + if (!kmalloc_ptr) + return -ENOMEM; + +- /* Position our struct dma_aligned_buffer such that data is aligned */ +- temp = PTR_ALIGN(kmalloc_ptr + 1, DWC2_USB_DMA_ALIGN) - 1; +- temp->kmalloc_ptr = kmalloc_ptr; +- temp->old_xfer_buffer = urb->transfer_buffer; ++ /* ++ * Position value of original urb->transfer_buffer pointer to the end ++ * of allocation for later referencing ++ */ ++ memcpy(kmalloc_ptr + urb->transfer_buffer_length, ++ &urb->transfer_buffer, sizeof(urb->transfer_buffer)); ++ + if (usb_urb_dir_out(urb)) +- memcpy(temp->data, urb->transfer_buffer, ++ memcpy(kmalloc_ptr, urb->transfer_buffer, + urb->transfer_buffer_length); +- urb->transfer_buffer = temp->data; ++ urb->transfer_buffer = kmalloc_ptr; + + urb->transfer_flags |= URB_ALIGNED_TEMP_BUFFER; + |