linux-kernel - Re: Issue with ioremap

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Message-ID: <20160331200147.GA20530@jcartwri.amer.corp.natinst.com>
Date:	Thu, 31 Mar 2016 15:01:47 -0500
From:	Josh Cartwright <joshc@...com>
To:	punnaiah choudary kalluri <punnaia@...inx.com>
Cc:	linux-mm@...ck.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Issue with ioremap

On Fri, Apr 01, 2016 at 01:13:06AM +0530, punnaiah choudary kalluri wrote:
> Hi,
> 
> We are using the pl353 smc controller for interfacing the nand in our zynq SOC.
> The driver for this controller is currently under mainline review.
> Recently we are moved to 4.4 kernel and observing issues with the driver.
> while debug, found that the issue is with the virtual address returned from
> the ioremap is not aligned to the physical address and causing nand
> access failures.
> the nand controller physical address starts at 0xE1000000 and the size is 16MB.
> the ioremap function in 4.3 kernel returns the virtual address that is
> aligned to the size
> but not the case in 4.4 kernel.

:(.  I had actually ran into this, too, as I was evaluating the use of
the upstream-targetted pl353 stuff; sorry I didn't say anything.

> this controller uses the bits [31:24] as base address and use rest all
> bits for configuring adders cycles, chip select information. so it
> expects the virtual address also aligned to 0xFF000000 otherwise the
> nand commands issued will fail.

The driver _currently_ expects the virtual address to be 16M aligned,
but is that a hard requirement?  It seems possible that the driver could
be written without this assumption, correct?

This would mean that the driver would need to maintain the cs/cycles
configuration state outside of the mapped virtual address, and then
calculate + add the calculated offset to the base.  Would that work?
I had been meaning to give it a try, but haven't gotten around to it.

  Josh