linux-kernel - Re: [PATCH] mtd: nand: stm_nand

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Message-ID: <20140806102641.GB10136@lee--X1>
Date:	Wed, 6 Aug 2014 11:26:41 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...inux.com, "Gupta, Pekon\"" <pekon@...com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
	Boris BREZILLON <b.brezillon.dev@...il.com>
Subject: Re: [PATCH] mtd: nand: stm_nand_bch: add new driver

On Wed, 02 Jul 2014, Brian Norris wrote:
> On Wed, May 28, 2014 at 10:20:05AM +0100, Lee Jones wrote:

[...]

> > +	if (((unsigned int)buf & (NANDI_BCH_DMA_ALIGNMENT - 1)) ||
> > +	    (!virt_addr_valid(buf))) /* vmalloc'd buffer! */
> > +		bounce = true;
> > +
> > +	p = bounce ? nandi->page_buf : buf;
> 
> It looks like you're reimplementing NAND_USE_BOUNCE_BUFFER. Can you try
> using that flag? (You may need to extend it to account for your DMA
> alignment, too.)

NAND_USE_BOUNCE_BUFFER won't work for us unless we can guarantee that
the bounce buffer will always be 64 Byte aligned, which I don't think
we can.  Another way to do it would be to assign all of our own
buffers, but I'm really not comfortable fiddling with those as there
are a lot of controller specific intricacies which a) I'm not familiar
with and b) no longer have Angus to fire questions off to and/or
review.

So if you don't mind, I'd really rather use Angus' implementation.
It's only an extra couple of lines and Angus has already tested it to
a high level.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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