Re: [PATCH v2] mtd: onenand: omap2: Disable DMA for HIGHMEM buffers

[Ladislav Michl <ladis@linux-mips.org>]

Hi Péter,

On Mon, Apr 16, 2018 at 02:34:54PM +0300, Peter Ujfalusi wrote:
> On 2018-04-16 09:52, Ladislav Michl wrote:
> > dma_map_single doesn't get the proper DMA address for vmalloced area,
> 
> Which is not a big surprise as vmalloc will allocate contiguous virtual
> memory (which might corresponds to non-contiguous physical memory). Even
> if you somehow get the physical address of the start of the vmalloced
> buffer, you don't really know how long that chunk is and where the
> buffer continues in physical memory.
> 
> Creating sg_list of the vmalloced buffer should be possible also by
> walking the virt memory and get the pages with vmalloc_to_page().
> I don't think there is a generic vmalloc_to_sg(), one can be implemented.

Please see previous bugreport here:
https://marc.info/?l=linux-omap&m=152337752611812&w=2

Unfortunately issue was noticed after v4.16 come out and v4.17-rc1 was
about to released. Thus safe change was introduced.

Best regards,
	ladis

> > so disable DMA in this case.
> > 
> > Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
> > Reported-by: "H. Nikolaus Schaller" <hns@goldelico.com>
> > Tested-by: "H. Nikolaus Schaller" <hns@goldelico.com>
> > ---
> >  Changes:
> >  -v2: Added Tested-by tag, based on v4.17-rc1 (no change in patch itself)
> > 
> >  drivers/mtd/nand/onenand/omap2.c | 105 +++++++++++--------------------
> >  1 file changed, 38 insertions(+), 67 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/onenand/omap2.c b/drivers/mtd/nand/onenand/omap2.c
> > index 9c159f0dd9a6..321137158ff3 100644
> > --- a/drivers/mtd/nand/onenand/omap2.c
> > +++ b/drivers/mtd/nand/onenand/omap2.c
> > @@ -375,56 +375,42 @@ static int omap2_onenand_read_bufferram(struct mtd_info *mtd, int area,
> >  {
> >  	struct omap2_onenand *c = container_of(mtd, struct omap2_onenand, mtd);
> >  	struct onenand_chip *this = mtd->priv;
> > -	dma_addr_t dma_src, dma_dst;
> > -	int bram_offset;
> > +	struct device *dev = &c->pdev->dev;
> >  	void *buf = (void *)buffer;
> > +	dma_addr_t dma_src, dma_dst;
> > +	int bram_offset, err;
> >  	size_t xtra;
> > -	int ret;
> >  
> >  	bram_offset = omap2_onenand_bufferram_offset(mtd, area) + area + offset;
> > -	if (bram_offset & 3 || (size_t)buf & 3 || count < 384)
> > -		goto out_copy;
> > -
> > -	/* panic_write() may be in an interrupt context */
> > -	if (in_interrupt() || oops_in_progress)
> > +	/*
> > +	 * If the buffer address is not DMA-able, len is not long enough to make
> > +	 * DMA transfers profitable or panic_write() may be in an interrupt
> > +	 * context fallback to PIO mode.
> > +	 */
> > +	if (!virt_addr_valid(buf) || bram_offset & 3 || (size_t)buf & 3 ||
> > +	    count < 384 || in_interrupt() || oops_in_progress )
> >  		goto out_copy;
> >  
> > -	if (buf >= high_memory) {
> > -		struct page *p1;
> > -
> > -		if (((size_t)buf & PAGE_MASK) !=
> > -		    ((size_t)(buf + count - 1) & PAGE_MASK))
> > -			goto out_copy;
> > -		p1 = vmalloc_to_page(buf);
> > -		if (!p1)
> > -			goto out_copy;
> > -		buf = page_address(p1) + ((size_t)buf & ~PAGE_MASK);
> > -	}
> > -
> >  	xtra = count & 3;
> >  	if (xtra) {
> >  		count -= xtra;
> >  		memcpy(buf + count, this->base + bram_offset + count, xtra);
> >  	}
> >  
> > +	dma_dst = dma_map_single(dev, buf, count, DMA_FROM_DEVICE);
> >  	dma_src = c->phys_base + bram_offset;
> > -	dma_dst = dma_map_single(&c->pdev->dev, buf, count, DMA_FROM_DEVICE);
> > -	if (dma_mapping_error(&c->pdev->dev, dma_dst)) {
> > -		dev_err(&c->pdev->dev,
> > -			"Couldn't DMA map a %d byte buffer\n",
> > -			count);
> > -		goto out_copy;
> > -	}
> >  
> > -	ret = omap2_onenand_dma_transfer(c, dma_src, dma_dst, count);
> > -	dma_unmap_single(&c->pdev->dev, dma_dst, count, DMA_FROM_DEVICE);
> > -
> > -	if (ret) {
> > -		dev_err(&c->pdev->dev, "timeout waiting for DMA\n");
> > +	if (dma_mapping_error(dev, dma_dst)) {
> > +		dev_err(dev, "Couldn't DMA map a %d byte buffer\n", count);
> >  		goto out_copy;
> >  	}
> >  
> > -	return 0;
> > +	err = omap2_onenand_dma_transfer(c, dma_src, dma_dst, count);
> > +	dma_unmap_single(dev, dma_dst, count, DMA_FROM_DEVICE);
> > +	if (!err)
> > +		return 0;
> > +
> > +	dev_err(dev, "timeout waiting for DMA\n");
> >  
> >  out_copy:
> >  	memcpy(buf, this->base + bram_offset, count);
> > @@ -437,49 +423,34 @@ static int omap2_onenand_write_bufferram(struct mtd_info *mtd, int area,
> >  {
> >  	struct omap2_onenand *c = container_of(mtd, struct omap2_onenand, mtd);
> >  	struct onenand_chip *this = mtd->priv;
> > -	dma_addr_t dma_src, dma_dst;
> > -	int bram_offset;
> > +	struct device *dev = &c->pdev->dev;
> >  	void *buf = (void *)buffer;
> > -	int ret;
> > +	dma_addr_t dma_src, dma_dst;
> > +	int bram_offset, err;
> >  
> >  	bram_offset = omap2_onenand_bufferram_offset(mtd, area) + area + offset;
> > -	if (bram_offset & 3 || (size_t)buf & 3 || count < 384)
> > -		goto out_copy;
> > -
> > -	/* panic_write() may be in an interrupt context */
> > -	if (in_interrupt() || oops_in_progress)
> > +	/*
> > +	 * If the buffer address is not DMA-able, len is not long enough to make
> > +	 * DMA transfers profitable or panic_write() may be in an interrupt
> > +	 * context fallback to PIO mode.
> > +	 */
> > +	if (!virt_addr_valid(buf) || bram_offset & 3 || (size_t)buf & 3 ||
> > +	    count < 384 || in_interrupt() || oops_in_progress )
> >  		goto out_copy;
> >  
> > -	if (buf >= high_memory) {
> > -		struct page *p1;
> > -
> > -		if (((size_t)buf & PAGE_MASK) !=
> > -		    ((size_t)(buf + count - 1) & PAGE_MASK))
> > -			goto out_copy;
> > -		p1 = vmalloc_to_page(buf);
> > -		if (!p1)
> > -			goto out_copy;
> > -		buf = page_address(p1) + ((size_t)buf & ~PAGE_MASK);
> > -	}
> > -
> > -	dma_src = dma_map_single(&c->pdev->dev, buf, count, DMA_TO_DEVICE);
> > +	dma_src = dma_map_single(dev, buf, count, DMA_TO_DEVICE);
> >  	dma_dst = c->phys_base + bram_offset;
> > -	if (dma_mapping_error(&c->pdev->dev, dma_src)) {
> > -		dev_err(&c->pdev->dev,
> > -			"Couldn't DMA map a %d byte buffer\n",
> > -			count);
> > -		return -1;
> > -	}
> > -
> > -	ret = omap2_onenand_dma_transfer(c, dma_src, dma_dst, count);
> > -	dma_unmap_single(&c->pdev->dev, dma_src, count, DMA_TO_DEVICE);
> > -
> > -	if (ret) {
> > -		dev_err(&c->pdev->dev, "timeout waiting for DMA\n");
> > +	if (dma_mapping_error(dev, dma_src)) {
> > +		dev_err(dev, "Couldn't DMA map a %d byte buffer\n", count);
> >  		goto out_copy;
> >  	}
> >  
> > -	return 0;
> > +	err = omap2_onenand_dma_transfer(c, dma_src, dma_dst, count);
> > +	dma_unmap_page(dev, dma_src, count, DMA_TO_DEVICE);
> > +	if (!err)
> > +		return 0;
> > +
> > +	dev_err(dev, "timeout waiting for DMA\n");
> >  
> >  out_copy:
> >  	memcpy(this->base + bram_offset, buf, count);
> > 
> 
> - Péter
> 
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