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Message-ID: <20101217223502.GB19418@suse.de>
Date: Fri, 17 Dec 2010 14:35:02 -0800
From: Greg KH <gregkh@...e.de>
To: Robert Morell <rmorell@...dia.com>
Cc: David Brownell <dbrownell@...rs.sourceforge.net>,
Benoit Goby <benoit@...roid.com>,
Alan Stern <stern@...land.harvard.edu>,
Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
Matthew Wilcox <willy@...ux.intel.com>,
Ming Lei <tom.leiming@...il.com>,
Jacob Pan <jacob.jun.pan@...el.com>,
Olof Johansson <olof@...om.net>,
Erik Gilling <konkers@...roid.com>,
Colin Cross <ccross@...roid.com>, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] USB: ehci: tegra: Align DMA transfers to 32 bytes
On Fri, Dec 17, 2010 at 01:58:49PM -0800, Robert Morell wrote:
> The Tegra2 USB controller doesn't properly deal with misaligned DMA
> buffers, causing corruption. This is especially prevalent with USB
> network adapters, where skbuff alignment is often in the middle of a
> 4-byte dword.
>
> To avoid this, allocate a temporary buffer for the DMA if the provided
> buffer isn't sufficiently aligned.
>
> Signed-off-by: Robert Morell <rmorell@...dia.com>
> Reviewed-by: Scott Williams <scwilliams@...dia.com>
> Reviewed-by: Janne Hellsten <jhellsten@...dia.com>
> ---
> drivers/usb/host/ehci-tegra.c | 94 +++++++++++++++++++++++++++++++++++++++++
> include/linux/usb.h | 1 +
> 2 files changed, 95 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c
> index d990c1c..a75e4db 100644
> --- a/drivers/usb/host/ehci-tegra.c
> +++ b/drivers/usb/host/ehci-tegra.c
> @@ -32,6 +32,10 @@
> #define TEGRA_USB_USBMODE_HOST (3 << 0)
> #define TEGRA_USB_PORTSC1_PTC(x) (((x) & 0xf) << 16)
>
> +#define TEGRA_USB_DMA_ALIGN 32
> +
> +#define URB_ALIGNED_TEMP_BUFFER 0x80000000
> +
> struct tegra_ehci_context {
> bool valid;
> u32 command;
> @@ -457,6 +461,94 @@ static int tegra_ehci_bus_resume(struct usb_hcd *hcd)
> }
> #endif
>
> +struct temp_buffer {
> + void *kmalloc_ptr;
> + void *old_xfer_buffer;
> + u8 data[0];
> +};
> +
> +static void free_temp_buffer(struct urb *urb)
> +{
> + enum dma_data_direction dir;
> + struct temp_buffer *temp;
> +
> + if (!(urb->transfer_flags & URB_ALIGNED_TEMP_BUFFER))
> + return;
> +
> + dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
> +
> + temp = container_of(urb->transfer_buffer, struct temp_buffer,
> + data);
> +
> + if (dir == DMA_FROM_DEVICE)
> + memcpy(temp->old_xfer_buffer, temp->data,
> + urb->transfer_buffer_length);
> + urb->transfer_buffer = temp->old_xfer_buffer;
> + kfree(temp->kmalloc_ptr);
> +
> + urb->transfer_flags &= ~URB_ALIGNED_TEMP_BUFFER;
> +}
> +
> +static int alloc_temp_buffer(struct urb *urb, gfp_t mem_flags)
> +{
> + enum dma_data_direction dir;
> + struct temp_buffer *temp, *kmalloc_ptr;
> + size_t kmalloc_size;
> + void *data;
> +
> + if (urb->num_sgs || urb->sg ||
> + urb->transfer_buffer_length == 0 ||
> + !((uintptr_t)urb->transfer_buffer & (TEGRA_USB_DMA_ALIGN - 1)))
> + return 0;
> +
> + dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
> +
> + /* Allocate a buffer with enough padding for alignment */
> + kmalloc_size = urb->transfer_buffer_length +
> + sizeof(struct temp_buffer) + TEGRA_USB_DMA_ALIGN - 1;
> +
> + kmalloc_ptr = kmalloc(kmalloc_size, mem_flags);
> + if (!kmalloc_ptr)
> + return -ENOMEM;
> +
> + /* Position our struct temp_buffer such that data is aligned */
> + temp = PTR_ALIGN(kmalloc_ptr + 1, TEGRA_USB_DMA_ALIGN) - 1;
> +
> + temp->kmalloc_ptr = kmalloc_ptr;
> + temp->old_xfer_buffer = urb->transfer_buffer;
> + if (dir == DMA_TO_DEVICE)
> + memcpy(temp->data, urb->transfer_buffer,
> + urb->transfer_buffer_length);
> + urb->transfer_buffer = temp->data;
> +
> + BUILD_BUG_ON(!(URB_ALIGNED_TEMP_BUFFER & URB_DRIVER_PRIVATE));
See below why this should be removed
> + urb->transfer_flags |= URB_ALIGNED_TEMP_BUFFER;
> +
> + return 0;
> +}
> +
> +static int tegra_ehci_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
> + gfp_t mem_flags)
> +{
> + int ret;
> +
> + ret = alloc_temp_buffer(urb, mem_flags);
> + if (ret)
> + return ret;
> +
> + ret = usb_hcd_map_urb_for_dma(hcd, urb, mem_flags);
> + if (ret)
> + free_temp_buffer(urb);
> +
> + return ret;
> +}
> +
> +static void tegra_ehci_unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
> +{
> + usb_hcd_unmap_urb_for_dma(hcd, urb);
> + free_temp_buffer(urb);
> +}
> +
> static const struct hc_driver tegra_ehci_hc_driver = {
> .description = hcd_name,
> .product_desc = "Tegra EHCI Host Controller",
> @@ -472,6 +564,8 @@ static const struct hc_driver tegra_ehci_hc_driver = {
> .shutdown = tegra_ehci_shutdown,
> .urb_enqueue = ehci_urb_enqueue,
> .urb_dequeue = ehci_urb_dequeue,
> + .map_urb_for_dma = tegra_ehci_map_urb_for_dma,
> + .unmap_urb_for_dma = tegra_ehci_unmap_urb_for_dma,
> .endpoint_disable = ehci_endpoint_disable,
> .endpoint_reset = ehci_endpoint_reset,
> .get_frame_number = ehci_get_frame,
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index 35fe6ab..cd07173 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -975,6 +975,7 @@ extern int usb_disabled(void);
> #define URB_SETUP_MAP_SINGLE 0x00100000 /* Setup packet DMA mapped */
> #define URB_SETUP_MAP_LOCAL 0x00200000 /* HCD-local setup packet */
> #define URB_DMA_SG_COMBINED 0x00400000 /* S-G entries were combined */
> +#define URB_DRIVER_PRIVATE 0x80000000 /* For driver-private use */
Um, what? You are using this for a build check, which seems pointless
as you already modified the code to not need this.
So it doesn't look like this is needed, right?
thanks,
greg k-h
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