linux-kernel - RE: [PATCH v2] usb: cdns3: Optimize DMA request buffer allocation

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Date:   Mon, 22 Mar 2021 10:30:53 +0000
From:   Sanket Parmar <sparmar@...ence.com>
To:     Peter Chen <peter.chen@...nel.org>
CC:     Pawel Laszczak <pawell@...ence.com>,
        "a-govindraju@...com" <a-govindraju@...com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rahul Kumar <kurahul@...ence.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "kishon@...com" <kishon@...com>,
        "hch@...radead.org" <hch@...radead.org>
Subject: RE: [PATCH v2] usb: cdns3: Optimize DMA request buffer allocation

Hi Peter,

> On 21-03-17 20:13:59, 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 dma_alloc_noncoherent()
> > to allocate aligned request buffer of dynamic length.
> >
> > Reported-by: Aswath Govindraju <a-govindraju@...com>
> > Signed-off-by: Sanket Parmar <sparmar@...ence.com>
> > ---
> >
> > Changelog:
> > v2:
> > - used dma_*_noncoherent() APIs
> > - changed the commit log
> >
> >  drivers/usb/cdns3/cdns3-gadget.c | 30 ++++++++++++++++++++++++-----
> -
> >  drivers/usb/cdns3/cdns3-gadget.h |  2 ++
> >  2 files changed, 26 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-
> gadget.c
> > index 0b892a2..126087b 100644
> > --- a/drivers/usb/cdns3/cdns3-gadget.c
> > +++ b/drivers/usb/cdns3/cdns3-gadget.c
> > @@ -819,9 +819,15 @@ void cdns3_gadget_giveback(struct
> cdns3_endpoint *priv_ep,
> >  					priv_ep->dir);
> >
> >  	if ((priv_req->flags & REQUEST_UNALIGNED) &&
> > -	    priv_ep->dir == USB_DIR_OUT && !request->status)
> > +	    priv_ep->dir == USB_DIR_OUT && !request->status) {
> > +		/* Make DMA buffer CPU accessible */
> > +		dma_sync_single_for_cpu(priv_dev->sysdev,
> > +			priv_req->aligned_buf->dma,
> > +			priv_req->aligned_buf->size,
> > +			priv_req->aligned_buf->dir);
> >  		memcpy(request->buf, priv_req->aligned_buf->buf,
> >  		       request->length);
> > +	}
> >
> >  	priv_req->flags &= ~(REQUEST_PENDING | REQUEST_UNALIGNED);
> >  	/* All TRBs have finished, clear the counter */
> > @@ -883,8 +889,8 @@ 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);
> > +			dma_free_noncoherent(priv_dev->sysdev, buf-
> >size,
> > +					  buf->buf, buf->dma, buf->dir);
> >  			kfree(buf);
> >  			spin_lock_irqsave(&priv_dev->lock, flags);
> >  		}
> > @@ -911,10 +917,13 @@ static int
> cdns3_prepare_aligned_request_buf(struct cdns3_request *priv_req)
> >  			return -ENOMEM;
> >
> >  		buf->size = priv_req->request.length;
> > +		buf->dir = usb_endpoint_dir_in(priv_ep->endpoint.desc) ?
> > +			DMA_TO_DEVICE : DMA_FROM_DEVICE;
> >
> > -		buf->buf = dma_alloc_coherent(priv_dev->sysdev,
> > +		buf->buf = dma_alloc_noncoherent(priv_dev->sysdev,
> >  					      buf->size,
> >  					      &buf->dma,
> > +					      buf->dir,
> >  					      GFP_ATOMIC);
> >  		if (!buf->buf) {
> >  			kfree(buf);
> > @@ -936,10 +945,18 @@ static int
> cdns3_prepare_aligned_request_buf(struct cdns3_request *priv_req)
> >  	}
> >
> >  	if (priv_ep->dir == USB_DIR_IN) {
> > +		/* Make DMA buffer CPU accessible */
> > +		dma_sync_single_for_cpu(priv_dev->sysdev,
> > +			buf->dma, buf->size, buf->dir);
> >  		memcpy(buf->buf, priv_req->request.buf,
> >  		       priv_req->request.length);
> >  	}
> >
> > +	/* Transfer DMA buffer ownership back to device */
> > +	dma_sync_single_for_device(priv_dev->sysdev,
> > +			buf->dma, buf->size, buf->dir);
> > +
> > +
> 
> One more blank line.
> 
> Otherwise, it seems OK for me.

I have remove this blank line. New patch has been posted already.

> 
> >  	priv_req->flags |= REQUEST_UNALIGNED;
> >  	trace_cdns3_prepare_aligned_request(priv_req);
> >
> > @@ -3088,9 +3105,10 @@ 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,
> > +		dma_free_noncoherent(priv_dev->sysdev, buf->size,
> >  				  buf->buf,
> > -				  buf->dma);
> > +				  buf->dma,
> > +				  buf->dir);
> >
> >  		list_del(&buf->list);
> >  		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;
> >  };
> > --
> > 2.4.5
> >
> 
> --
> 
> Thanks,
> Peter Chen

Thanks,
Sanket