linux-kernel - Re: USB mass storage and ARM cache coherency

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Date:	Tue, 02 Feb 2010 12:01:12 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Matthew Dharm <mdharm-kernel@...-eyed-alien.net>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Ming Lei <tom.leiming@...il.com>, linux-usb@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Sebastian Siewior <bigeasy@...utronix.de>,
	Greg KH <greg@...ah.com>
Subject: Re: USB mass storage and ARM cache coherency

On Tue, 2010-02-02 at 11:48 +0000, Oliver Neukum wrote:
> Am Montag, 1. Februar 2010 18:29:14 schrieb Catalin Marinas:
> > +       if (usb_pipein(urb->pipe) && usb_pipetype(urb->pipe) == PIPE_BULK) {
> > +               void *ptr;
> > +               for (ptr = urb->transfer_buffer;
> > +                    ptr < urb->transfer_buffer + urb->transfer_buffer_length;
> > +                    ptr += PAGE_SIZE)
> > +                       flush_dcache_page(virt_to_page(ptr));
> 
> Is it correct to limit this to BULK pipes?

I'm not entirely sure. The flush_dcache_page() should only be called for
pages that may be mapped into user space (page cache pages). We don't
need this for control buffers. It was my impression that what's coming
from the mass storage layer intended for page cache pages has the
PIPE_BULK type (I may be wrong though).

-- 
Catalin

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