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SubjectRe: [PATCH v2] mtd: onenand: omap2: Disable DMA for HIGHMEM buffers
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
>
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

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