kernel: usb: dwc2 DMA alignment fixes
Add two patches submitted for upstream review that significantly improve the dwc2 driver on openwrt from kernel stability and performance perspectives. Fixes: FS#1367 Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
This commit is contained in:
Antti Seppälä
Hauke Mehrtens
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commit
9f451ec698
2 changed files with 176 additions and 0 deletions
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From 028c9191bdf88f120f65626920a6a679170fcc3e Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Antti=20Sepp=C3=A4l=C3=A4?= <a.seppala@gmail.com>
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Date: Thu, 5 Jul 2018 11:37:03 +0300
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Subject: [PATCH 1/2] usb: dwc2: Fix DMA alignment to start at allocated
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boundary
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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The commit 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more
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supported way") introduced a common way to align DMA allocations.
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The code in the commit aligns the struct dma_aligned_buffer but the
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actual DMA address pointed by data[0] gets aligned to an offset from
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the allocated boundary by the kmalloc_ptr and the old_xfer_buffer
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pointers.
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This is against the recommendation in Documentation/DMA-API.txt which
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states:
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Therefore, it is recommended that driver writers who don't take
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special care to determine the cache line size at run time only map
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virtual regions that begin and end on page boundaries (which are
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guaranteed also to be cache line boundaries).
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The effect of this is that architectures with non-coherent DMA caches
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may run into memory corruption or kernel crashes with Unhandled
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kernel unaligned accesses exceptions.
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Fix the alignment by positioning the DMA area in front of the allocation
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and use memory at the end of the area for storing the orginal
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transfer_buffer pointer. This may have the added benefit of increased
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performance as the DMA area is now fully aligned on all architectures.
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Tested with Lantiq xRX200 (MIPS) and RPi Model B Rev 2 (ARM).
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Fixes: 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in a more
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supported way")
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Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
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---
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drivers/usb/dwc2/hcd.c | 44 +++++++++++++++++++++++---------------------
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1 file changed, 23 insertions(+), 21 deletions(-)
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--- a/drivers/usb/dwc2/hcd.c
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+++ b/drivers/usb/dwc2/hcd.c
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@@ -2628,34 +2628,29 @@ static void dwc2_hc_init_xfer(struct dwc
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#define DWC2_USB_DMA_ALIGN 4
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-struct dma_aligned_buffer {
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- void *kmalloc_ptr;
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- void *old_xfer_buffer;
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- u8 data[0];
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-};
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-
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static void dwc2_free_dma_aligned_buffer(struct urb *urb)
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{
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- struct dma_aligned_buffer *temp;
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+ void *stored_xfer_buffer;
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if (!(urb->transfer_flags & URB_ALIGNED_TEMP_BUFFER))
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return;
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- temp = container_of(urb->transfer_buffer,
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- struct dma_aligned_buffer, data);
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+ /* Restore urb->transfer_buffer from the end of the allocated area */
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+ memcpy(&stored_xfer_buffer, urb->transfer_buffer +
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+ urb->transfer_buffer_length, sizeof(urb->transfer_buffer));
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if (usb_urb_dir_in(urb))
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- memcpy(temp->old_xfer_buffer, temp->data,
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+ memcpy(stored_xfer_buffer, urb->transfer_buffer,
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urb->transfer_buffer_length);
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- urb->transfer_buffer = temp->old_xfer_buffer;
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- kfree(temp->kmalloc_ptr);
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+ kfree(urb->transfer_buffer);
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+ urb->transfer_buffer = stored_xfer_buffer;
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urb->transfer_flags &= ~URB_ALIGNED_TEMP_BUFFER;
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}
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static int dwc2_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags)
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{
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- struct dma_aligned_buffer *temp, *kmalloc_ptr;
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+ void *kmalloc_ptr;
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size_t kmalloc_size;
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if (urb->num_sgs || urb->sg ||
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@@ -2663,22 +2658,29 @@ static int dwc2_alloc_dma_aligned_buffer
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!((uintptr_t)urb->transfer_buffer & (DWC2_USB_DMA_ALIGN - 1)))
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return 0;
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- /* Allocate a buffer with enough padding for alignment */
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+ /*
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+ * Allocate a buffer with enough padding for original transfer_buffer
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+ * pointer. This allocation is guaranteed to be aligned properly for
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+ * DMA
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+ */
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kmalloc_size = urb->transfer_buffer_length +
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- sizeof(struct dma_aligned_buffer) + DWC2_USB_DMA_ALIGN - 1;
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+ sizeof(urb->transfer_buffer);
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kmalloc_ptr = kmalloc(kmalloc_size, mem_flags);
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if (!kmalloc_ptr)
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return -ENOMEM;
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- /* Position our struct dma_aligned_buffer such that data is aligned */
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- temp = PTR_ALIGN(kmalloc_ptr + 1, DWC2_USB_DMA_ALIGN) - 1;
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- temp->kmalloc_ptr = kmalloc_ptr;
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- temp->old_xfer_buffer = urb->transfer_buffer;
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+ /*
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+ * Position value of original urb->transfer_buffer pointer to the end
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+ * of allocation for later referencing
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+ */
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+ memcpy(kmalloc_ptr + urb->transfer_buffer_length,
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+ &urb->transfer_buffer, sizeof(urb->transfer_buffer));
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+
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if (usb_urb_dir_out(urb))
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- memcpy(temp->data, urb->transfer_buffer,
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+ memcpy(kmalloc_ptr, urb->transfer_buffer,
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urb->transfer_buffer_length);
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- urb->transfer_buffer = temp->data;
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+ urb->transfer_buffer = kmalloc_ptr;
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urb->transfer_flags |= URB_ALIGNED_TEMP_BUFFER;
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@ -0,0 +1,50 @@
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From 81da1738eee68f1961e03bdeb2d60cf0eb4dd713 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Antti=20Sepp=C3=A4l=C3=A4?= <a.seppala@gmail.com>
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Date: Thu, 5 Jul 2018 12:06:18 +0300
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Subject: [PATCH 2/2] usb: dwc2: Fix inefficient copy of unaligned buffers
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Make sure only to copy any actual data rather than the whole buffer,
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when releasing the temporary buffer used for unaligned non-isochronous
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transfers.
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Taken directly from commit 0efd937e27d5e ("USB: ehci-tegra: fix inefficient
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copy of unaligned buffers")
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Tested with Lantiq xRX200 (MIPS) and RPi Model B Rev 2 (ARM)
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Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
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---
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drivers/usb/dwc2/hcd.c | 12 +++++++++---
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1 file changed, 9 insertions(+), 3 deletions(-)
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--- a/drivers/usb/dwc2/hcd.c
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+++ b/drivers/usb/dwc2/hcd.c
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@@ -2631,6 +2631,7 @@ static void dwc2_hc_init_xfer(struct dwc
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static void dwc2_free_dma_aligned_buffer(struct urb *urb)
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{
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void *stored_xfer_buffer;
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+ size_t length;
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if (!(urb->transfer_flags & URB_ALIGNED_TEMP_BUFFER))
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return;
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@@ -2639,9 +2640,14 @@ static void dwc2_free_dma_aligned_buffer
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memcpy(&stored_xfer_buffer, urb->transfer_buffer +
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urb->transfer_buffer_length, sizeof(urb->transfer_buffer));
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- if (usb_urb_dir_in(urb))
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- memcpy(stored_xfer_buffer, urb->transfer_buffer,
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- urb->transfer_buffer_length);
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+ if (usb_urb_dir_in(urb)) {
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+ if (usb_pipeisoc(urb->pipe))
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+ length = urb->transfer_buffer_length;
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+ else
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+ length = urb->actual_length;
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+
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+ memcpy(stored_xfer_buffer, urb->transfer_buffer, length);
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+ }
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kfree(urb->transfer_buffer);
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urb->transfer_buffer = stored_xfer_buffer;
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