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Date:   Wed, 11 Apr 2018 09:36:56 +0200
From:   Ladislav Michl <ladis@linux-mips.org>
To:     Boris Brezillon <boris.brezillon@bootlin.com>
Cc:     Andreas Kemnade <andreas@kemnade.info>,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        Tony Lindgren <tony@atomide.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Ujfalusi <peter.ujfalusi@ti.com>,
        linux-omap <linux-omap@vger.kernel.org>,
        Roger Quadros <rogerq@ti.com>
Subject: Re: [Letux-kernel] [Bug]: mtd: onenand: omap2plus: kernel panic with
 OneNAND on OMAP3 (DM3730) device GTA04A5
Message-ID: <20180411073655.GA18273@lenoch>
References: <5D496D5C-4E3E-47B4-9981-E8F4C348DE00@goldelico.com>
 <20180410205643.GA2228@lenoch>
 <20180411065836.7e1bfc3f@aktux>
 <20180411062607.GA9179@lenoch>
 <20180411091528.4e954c32@bbrezillon>
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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@linux-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@linux-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;
> >  	}
> >