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Date: Sun, 14 Mar 2021 13:10:48 +0800
From: Peter Chen <peter.chen@...nel.org>
To: Sanket Parmar <sparmar@...ence.com>
Cc: pawell@...ence.com, a-govindraju@...com, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org, kurahul@...ence.com,
gregkh@...uxfoundation.org, kishon@...com
Subject: Re: [PATCH 2/2] usb: cdns3: Optimize DMA request buffer allocation
On 21-03-09 06:19:40, Sanket Parmar wrote:
> dma_alloc_coherent() might fail on the platform with a small DMA region.
>
> To avoid such failure in cdns3_prepare_aligned_request_buf(),
> dma_alloc_coherent() is replaced with kmalloc and dma_map API to
> allocate aligned request buffer of dynamic length.
>
> Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
The comment with the 1st patch, it is not a bug-fix.
> Reported-by: Aswath Govindraju <a-govindraju@...com>
> Signed-off-by: Sanket Parmar <sparmar@...ence.com>
> ---
> drivers/usb/cdns3/cdns3-gadget.c | 73 +++++++++++++++++++++++++------------
> drivers/usb/cdns3/cdns3-gadget.h | 2 +
> 2 files changed, 51 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
> index 5f51215..b4955ce 100644
> --- a/drivers/usb/cdns3/cdns3-gadget.c
> +++ b/drivers/usb/cdns3/cdns3-gadget.c
> @@ -818,10 +818,26 @@ void cdns3_gadget_giveback(struct cdns3_endpoint *priv_ep,
> usb_gadget_unmap_request_by_dev(priv_dev->sysdev, request,
> priv_ep->dir);
>
> - if ((priv_req->flags & REQUEST_UNALIGNED) &&
> - priv_ep->dir == USB_DIR_OUT && !request->status)
> - memcpy(request->buf, priv_req->aligned_buf->buf,
> - request->length);
> + if ((priv_req->flags & REQUEST_UNALIGNED) && priv_req->aligned_buf) {
> + struct cdns3_aligned_buf *buf;
> +
> + buf = priv_req->aligned_buf;
> + dma_unmap_single(priv_dev->sysdev, buf->dma, buf->size,
> + buf->dir);
> + priv_req->flags &= ~REQUEST_UNALIGNED;
> +
> + if (priv_ep->dir == USB_DIR_OUT && !request->status) {
> + memcpy(request->buf, priv_req->aligned_buf->buf,
> + request->length);
> + }
> +
> + trace_cdns3_free_aligned_request(priv_req);
> + priv_req->aligned_buf->in_use = 0;
> + queue_work(system_freezable_wq,
> + &priv_dev->aligned_buf_wq);
> + priv_req->aligned_buf = NULL;
> +
> + }
>
> priv_req->flags &= ~(REQUEST_PENDING | REQUEST_UNALIGNED);
> /* All TRBs have finished, clear the counter */
> @@ -883,8 +899,7 @@ static void cdns3_free_aligned_request_buf(struct work_struct *work)
> * interrupts.
> */
> spin_unlock_irqrestore(&priv_dev->lock, flags);
> - dma_free_coherent(priv_dev->sysdev, buf->size,
> - buf->buf, buf->dma);
> + kfree(buf->buf);
> kfree(buf);
> spin_lock_irqsave(&priv_dev->lock, flags);
> }
> @@ -910,27 +925,16 @@ static int cdns3_prepare_aligned_request_buf(struct cdns3_request *priv_req)
> if (!buf)
> return -ENOMEM;
>
> - buf->size = priv_req->request.length;
> + buf->size = usb_endpoint_dir_out(priv_ep->endpoint.desc) ?
> + usb_ep_align(&(priv_ep->endpoint), priv_req->request.length)
> + : priv_req->request.length;
>
> - buf->buf = dma_alloc_coherent(priv_dev->sysdev,
> - buf->size,
> - &buf->dma,
> - GFP_ATOMIC);
> + buf->buf = kmalloc(buf->size, GFP_ATOMIC);
> if (!buf->buf) {
> kfree(buf);
> return -ENOMEM;
> }
>
> - if (priv_req->aligned_buf) {
> - trace_cdns3_free_aligned_request(priv_req);
> - priv_req->aligned_buf->in_use = 0;
> - queue_work(system_freezable_wq,
> - &priv_dev->aligned_buf_wq);
> - }
> -
> - buf->in_use = 1;
> - priv_req->aligned_buf = buf;
> -
> list_add_tail(&buf->list,
> &priv_dev->aligned_buf_list);
> }
> @@ -940,6 +944,27 @@ static int cdns3_prepare_aligned_request_buf(struct cdns3_request *priv_req)
> priv_req->request.length);
> }
>
> + if (priv_req->aligned_buf) {
> + trace_cdns3_free_aligned_request(priv_req);
> + priv_req->aligned_buf->in_use = 0;
> + queue_work(system_freezable_wq,
> + &priv_dev->aligned_buf_wq);
@Pawel, do you remember when this condition is met?
> + }
> +
> + buf->dir = priv_ep->dir ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
> + buf->in_use = 1;
> + priv_req->aligned_buf = buf;
> +
> + buf->dma = dma_map_single(priv_dev->sysdev, buf->buf, buf->size,
> + buf->dir);
> +
> + if (dma_mapping_error(priv_dev->sysdev, buf->dma)) {
> + dev_err(priv_dev->dev, "Failed to map buffer\n");
> + kfree(buf->buf);
> + kfree(buf);
> + return -EFAULT;
> + }
> +
> priv_req->flags |= REQUEST_UNALIGNED;
> trace_cdns3_prepare_aligned_request(priv_req);
>
> @@ -3088,11 +3113,11 @@ static void cdns3_gadget_exit(struct cdns *cdns)
> struct cdns3_aligned_buf *buf;
>
> buf = cdns3_next_align_buf(&priv_dev->aligned_buf_list);
> - dma_free_coherent(priv_dev->sysdev, buf->size,
> - buf->buf,
> - buf->dma);
> + dma_unmap_single(priv_dev->sysdev, buf->dma, buf->size,
> + buf->dir);
It only needs to DMA unmap after DMA has completed, this buf will not be
used, otherwise, the kfree below will cause issue.
>
> list_del(&buf->list);
> + kfree(buf->buf);
> kfree(buf);
> }
>
> diff --git a/drivers/usb/cdns3/cdns3-gadget.h b/drivers/usb/cdns3/cdns3-gadget.h
> index ecf9b91..c5660f2 100644
> --- a/drivers/usb/cdns3/cdns3-gadget.h
> +++ b/drivers/usb/cdns3/cdns3-gadget.h
> @@ -12,6 +12,7 @@
> #ifndef __LINUX_CDNS3_GADGET
> #define __LINUX_CDNS3_GADGET
> #include <linux/usb/gadget.h>
> +#include <linux/dma-direction.h>
>
> /*
> * USBSS-DEV register interface.
> @@ -1205,6 +1206,7 @@ struct cdns3_aligned_buf {
> void *buf;
> dma_addr_t dma;
> u32 size;
> + enum dma_data_direction dir;
> unsigned in_use:1;
> struct list_head list;
> };
> --
> 1.7.1
>
--
Thanks,
Peter Chen
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