Re: Issue with ioremap

[Laura Abbott]

(cc linux-arm)

On 03/31/2016 01:01 PM, Josh Cartwright wrote:
> 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

I was curious so I took a look and this seems to be caused by

commit 803e3dbcb4cf80c898faccf01875f6ff6e5e76fd
Author: Sergey Dyasly <dserrg@xxxxxxxxx>
Date:   Wed Sep 9 16:27:18 2015 +0100

    ARM: 8430/1: use default ioremap alignment for SMP or LPAE
    
    16MB alignment for ioremap mappings was added by commit a069c896d0d6 ("[ARM]
    3705/1: add supersection support to ioremap()") in order to support supersection
    mappings. But __arm_ioremap_pfn_caller uses section and supersection mappings
    only in !SMP && !LPAE case. There is no need for such big alignment if either
    SMP or LPAE is enabled.
    
    After this change, ioremap will use default maximum alignment of 128 pages.
    
    Link: https://lkml.kernel.org/g/1419328813-2211-1-git-send-email-d.safonov@xxxxxxxxxxxxxxxxxxx
    
    Cc: Guan Xuetao <gxt@xxxxxxxxxxxxxxx>
    Cc: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>
    Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx>
    Cc: Will Deacon <will.deacon@xxxxxxx>
    Cc: Arnd Bergmann <arnd.bergmann@xxxxxxxxxx>
    Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
    Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Cc: Dmitry Safonov <d.safonov@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sergey Dyasly <s.dyasly@xxxxxxxxxxx>
    Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>

The thread assumed the higher alignment behavior was only needed for super
section mappings. Apparently not.

Thanks,
Laura