linux-kernel - Re: [PATCH 2/2] spi: Add SPI master controller for OCTEON SOCs.

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Date:	Tue, 21 Aug 2012 12:30:18 -0700
From:	David Daney <ddaney.cavm@...il.com>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	devicetree-discuss@...ts.ozlabs.org,
	Rob Herring <rob.herring@...xeda.com>,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 2/2] spi: Add SPI master controller for OCTEON SOCs.

On 05/19/2012 10:46 PM, Grant Likely wrote:
> On Fri, 11 May 2012 14:34:46 -0700, David Daney <ddaney.cavm@...il.com> wrote:
>> From: David Daney <david.daney@...ium.com>
>>
>> Add the driver, link it into the kbuild system and provide device tree
>> binding documentation.
>>
>> Signed-off-by: David Daney <david.daney@...ium.com>
>
> Some comments below, but you can add my a-b:
>
> Acked-by: Grant Likely <grant.likely@...retlab.ca>
>
[...]
>> +	p->register_base = (u64)devm_ioremap(&pdev->dev, res_mem->start,
>> +					     resource_size(res_mem));
>
> Nasty cast.  p->register_base needs to be an __iomem pointer
> variable.

No, it is only ever used as an argument to cvmx_{read,write}_csr(),
which want the u64 type.

>  The fact taht cvmx_read_csr accepts a uint64_t instead of
> an __iomem pointer looks really wrong.  Why is it written that way?


Register addresses on OCTEON are 64-bits wide.  In a 32-bit kernel,
pointers are only 32-bits wide.  Thus was born the cvmx_read_csr()
function that takes a u64 address.

We no longer support 32-bit kernels, but the legacy of the interface
lives on.

David Daney

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