linux-kernel - Re: [PATCH] Fix Oops with Atmel SPI

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Message-Id: <201005241109.20290.ian@brightstareng.com>
Date:	Mon, 24 May 2010 11:09:20 -0400
From:	Ian McDonnell <ian@...ghtstareng.com>
To:	Anders Larsen <al@...rsen.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Iwo Mergler <iwo@...l-direct.com.au>,
	linux-mtd@...ts.infradead.org,
	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>,
	Nicolas Pitre <nico@...xnic.net>, linux-kernel@...r.kernel.org,
	Matthias Kaehlcke <matthias@...hlcke.net>,
	David Woodhouse <dwmw2@...radead.org>,
	Haavard Skinnemoen <hskinnemoen@...el.com>
Subject: Re: [PATCH] Fix Oops with Atmel SPI

Anders,

I just tested one path, the "if (xfer->rx_buf)...", on
2.6.33 plus the at91 patch
http://maxim.org.za/AT91RM9200/2.6/2.6.33-at91.patch.gz
running on AT91SAM9260.

The test case involved doing i/o via the /dev/mtdblock
interface -- but this only exercises the rx_buf/vmalloc path --
MTD reads a block into the cache-buf to merge the write data. Not 
sure that we have any use cases for the tx_buf path using MTD.

-Ian

On Friday 21 May 2010, Andrew Morton wrote:
> On Wed, 19 May 2010 13:05:00 +0200
>
> Anders Larsen <al@...rsen.net> wrote:
> > On 2010-04-22 00:24:10, Andrew Morton wrote:
> > > Finally..  Wouldn't it be better to just fix the atmel SPI
> > > driver so that it doesn't barf when handed vmalloc'ed
> > > memory?  Who do we ridicule about that?  <checks, adds cc>
> >
> > You mean something like this instead?
>
> That looks simple enough.  How do we get it tested,
> changelogged and merged up?  Haavard, can you please take a
> look?
>
> > diff --git a/drivers/spi/atmel_spi.c
> > b/drivers/spi/atmel_spi.c index c4e0442..a9ad5e8 100644
> > --- a/drivers/spi/atmel_spi.c
> > +++ b/drivers/spi/atmel_spi.c
> > @@ -352,16 +352,30 @@ atmel_spi_dma_map_xfer(struct
> > atmel_spi *as, struct spi_transfer *xfer)
> >
> >  	xfer->tx_dma = xfer->rx_dma = INVALID_DMA_ADDRESS;
> >  	if (xfer->tx_buf) {
> > -		xfer->tx_dma = dma_map_single(dev,
> > -				(void *) xfer->tx_buf, xfer->len,
> > -				DMA_TO_DEVICE);
> > +		if (is_vmalloc_addr(xfer->tx_buf))
> > +			xfer->tx_dma = dma_map_page(dev,
> > +					vmalloc_to_page(xfer->tx_buf),
> > +					(unsigned long)xfer->tx_buf & (PAGE_SIZE-1),
> > +					xfer->len,
> > +					DMA_TO_DEVICE);
> > +		else
> > +			xfer->tx_dma = dma_map_single(dev,
> > +					(void *) xfer->tx_buf, xfer->len,
> > +					DMA_TO_DEVICE);
> >  		if (dma_mapping_error(dev, xfer->tx_dma))
> >  			return -ENOMEM;
> >  	}
> >  	if (xfer->rx_buf) {
> > -		xfer->rx_dma = dma_map_single(dev,
> > -				xfer->rx_buf, xfer->len,
> > -				DMA_FROM_DEVICE);
> > +		if (is_vmalloc_addr(xfer->rx_buf))
> > +			xfer->rx_dma = dma_map_page(dev,
> > +					vmalloc_to_page(xfer->rx_buf),
> > +					(unsigned long)xfer->rx_buf & (PAGE_SIZE-1),
> > +					xfer->len,
> > +					DMA_FROM_DEVICE);
> > +		else
> > +			xfer->rx_dma = dma_map_single(dev,
> > +					xfer->rx_buf, xfer->len,
> > +					DMA_FROM_DEVICE);
> >  		if (dma_mapping_error(dev, xfer->rx_dma)) {
> >  			if (xfer->tx_buf)
> >  				dma_unmap_single(dev,


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