[U-Boot] [PATCH] NAND: Allow per-buffer allocation
Marek Vasut
marek.vasut at gmail.com
Wed Aug 10 01:15:19 CEST 2011
On Wednesday, August 10, 2011 12:37:29 AM Scott Wood wrote:
> On 08/09/2011 04:54 PM, Marek Vasut wrote:
> > Don't allocate NAND buffers as one block, but allocate them separately.
> > This allows systems where DMA to buffers happen to allocate these
> > buffers properly aligned.
> >
> > Signed-off-by: Marek Vasut <marek.vasut at gmail.com>
>
> That second sentence is hard to parse -- I think you mean something
> like, "This accommodates drivers which DMA to the buffers and have
> alignment constraints."
Yes, something like that. Sorry, it's 1.14 PM here.
>
> Will a similar change be needed in Linux?
I'm not sure how much in sync we are with linux here. It'd be worth looking at.
>
> > int nand_scan_tail(struct mtd_info *mtd)
> > {
> >
> > - int i;
> > + int i, bufsize;
> > + uint8_t *buf;
> >
> > struct nand_chip *chip = mtd->priv;
> >
> > - if (!(chip->options & NAND_OWN_BUFFERS))
> > - chip->buffers = kmalloc(sizeof(*chip->buffers), GFP_KERNEL);
> > - if (!chip->buffers)
> > + if (!(chip->options & NAND_OWN_BUFFERS)) {
> > + chip->buffers = malloc(sizeof(struct nand_buffers));
> > + if (!chip->buffers)
> > + return -ENOMEM;
>
> Why does the struct itself need to be dynamically allocated?
That was in the NOTE: ... to avoid breaking drivers. We can have that changed,
but that'd be much more intrussive.
>
> > +
> > + bufsize = NAND_MAX_PAGESIZE + (3 * NAND_MAX_OOBSIZE);
> > + buf = malloc(bufsize);
> > +
> > + chip->buffers->buffer = (struct nand_buffers *)buf;
> > + chip->buffers->ecccalc = buf;
> > + chip->buffers->ecccode = buf + NAND_MAX_OOBSIZE;
> > + chip->buffers->databuf = buf + (2 * NAND_MAX_OOBSIZE);
> > + }
> > +
> > + if (!chip->buffers->buffer)
> >
> > return -ENOMEM;
>
> What does "buffer" mean now? What would a driver that supplies its own
> completely separate ecccalc/ecccode/databuf buffers put in "buffer"?
Maybe that condition should go also into the if() statement above. What do you
think ?
>
> -Scott
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