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Date: Wed, 11 Apr 2018 09:36:56 +0200
From: Ladislav Michl <ladis@...ux-mips.org>
To: Boris Brezillon <boris.brezillon@...tlin.com>
Cc: Andreas Kemnade <andreas@...nade.info>,
Discussions about the Letux Kernel
<letux-kernel@...nphoenux.org>,
Boris Brezillon <boris.brezillon@...e-electrons.com>,
Aaro Koskinen <aaro.koskinen@....fi>,
Tony Lindgren <tony@...mide.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Ujfalusi <peter.ujfalusi@...com>,
linux-omap <linux-omap@...r.kernel.org>,
Roger Quadros <rogerq@...com>
Subject: Re: [Letux-kernel] [Bug]: mtd: onenand: omap2plus: kernel panic with
OneNAND on OMAP3 (DM3730) device GTA04A5
Hi Boris,
On Wed, Apr 11, 2018 at 09:15:28AM +0200, Boris Brezillon wrote:
> Hi Ladislav,
>
> On Wed, 11 Apr 2018 08:26:07 +0200
> Ladislav Michl <ladis@...ux-mips.org> wrote:
>
> > Hi Andreas,
> >
> > On Wed, Apr 11, 2018 at 06:59:03AM +0200, Andreas Kemnade wrote:
> > > Hi Ladis,
> > >
> > > On Tue, 10 Apr 2018 22:56:43 +0200
> > > Ladislav Michl <ladis@...ux-mips.org> wrote:
> > >
> > > > Hi Nikolaus,
> > > >
> > > > On Tue, Apr 10, 2018 at 06:25:17PM +0200, H. Nikolaus Schaller wrote:
> > > > > Hi,
> > > > > we just started testing the v4.16 kernel and found the
> > > > > device no longer bootable (works with v4.15). It turned
> > > > > out that there was a harmful modification somewhere between
> > > > > v4.15.0 and v4.16-rc1.
> > > > >
> > > > > A git bisect points to this patch:
> > > >
> > > > Well, that's a shame... However, this code is in production for several
> > > > months now, so could you, please put 'goto out_copy' if 'buf >= high_memory'
> > > > condition is met, ie:
> > > > --- a/drivers/mtd/nand/onenand/omap2.c
> > > > +++ b/drivers/mtd/nand/onenand/omap2.c
> > > > @@ -392,6 +392,7 @@ static int omap2_onenand_read_bufferram(struct mtd_info *mtd, int area,
> > > > if (buf >= high_memory) {
> > > > struct page *p1;
> > > >
> > > > + goto out_copy;
> > > > if (((size_t)buf & PAGE_MASK) !=
> > > > ((size_t)(buf + count - 1) & PAGE_MASK))
> > > > goto out_copy;
> > >
> > > I had the same problem here, and that snippet helps here. ubiattach
> > > -p /dev/mtdX does not cause kernel oopses here anymore
> >
> > It seems reviving old code always comes at a price :-) Could you try
> > following patch, so far compile tested only?
> > (we'll need to do the same for omap2_onenand_write_bufferram, but
> > it sould be enough for testing purposes now)
> >
> > diff --git a/drivers/mtd/nand/onenand/omap2.c b/drivers/mtd/nand/onenand/omap2.c
> > index 9c159f0dd9a6..04cefd7a6487 100644
> > --- a/drivers/mtd/nand/onenand/omap2.c
> > +++ b/drivers/mtd/nand/onenand/omap2.c
> > @@ -375,11 +375,12 @@ 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;
> > + struct device *dev = &c->pdev->dev;
> > dma_addr_t dma_src, dma_dst;
> > int bram_offset;
> > void *buf = (void *)buffer;
> > size_t xtra;
> > - int ret;
> > + int ret, page_dma = 0;
> >
> > bram_offset = omap2_onenand_bufferram_offset(mtd, area) + area + offset;
> > if (bram_offset & 3 || (size_t)buf & 3 || count < 384)
> > @@ -389,38 +390,43 @@ static int omap2_onenand_read_bufferram(struct mtd_info *mtd, int area,
> > if (in_interrupt() || oops_in_progress)
> > goto out_copy;
> >
> > + xtra = count & 3;
> > + if (xtra) {
> > + count -= xtra;
> > + memcpy(buf + count, this->base + bram_offset + count, xtra);
> > + }
> > +
> > + /* Handle vmalloc address */
> > if (buf >= high_memory) {
> > - struct page *p1;
> > + struct page *page;
> >
> > if (((size_t)buf & PAGE_MASK) !=
> > ((size_t)(buf + count - 1) & PAGE_MASK))
> > goto out_copy;
> > - p1 = vmalloc_to_page(buf);
> > - if (!p1)
> > + page = vmalloc_to_page(buf);
>
> Not sure this approach is safe on all archs: if the cache is VIVT or
> VIPT, you may have several entries pointing to the same phys page, and
> then, when dma_map_page() does its cache maintenance operations, it's
> only taking one of these entries into account.
Hmm, I used the same approach Samsung OneNAND driver does since commit
dcf08227e964a53a2cb39130b74842c7dcb6adde.
Both TI OMAP3630 and Samsung S5PC110 are using Cortex-A8 which
is VIPT. In that case samsung's driver code has the same problem.
> In other parts of the MTD subsystem, we tend to not do DMA on buffers
> that have been vmalloc-ed.
>
> You can do something like
>
> if (virt_addr_valid(buf))
> /* Use DMA */
> else
> /*
> * Do not use DMA, or use a bounce buffer
> * allocated with kmalloc
> */
Okay, I'll use this approach then, but first I'd like to be sure above is
correct. Anyone?
> Regards,
>
> Boris
Thank you,
ladis
> > + if (!page)
> > 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);
> > + page_dma = 1;
> > + dma_dst = dma_map_page(dev, page, (size_t) buf & ~PAGE_MASK,
> > + count, DMA_FROM_DEVICE);
> > + } else {
> > + 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);
> > +
> > + if (dma_mapping_error(dev, dma_dst)) {
> > + dev_err(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 (page_dma)
> > + dma_unmap_page(dev, dma_dst, count, DMA_FROM_DEVICE);
> > + else
> > + dma_unmap_single(dev, dma_dst, count, DMA_FROM_DEVICE);
> >
> > if (ret) {
> > - dev_err(&c->pdev->dev, "timeout waiting for DMA\n");
> > + dev_err(dev, "timeout waiting for DMA\n");
> > goto out_copy;
> > }
> >
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