From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
Subject: Re: [PATCH 03/11] gpio: tegra: fix register address calculations
 for Tegra30
Date: Wed, 04 Apr 2012 12:53:07 -0600
Message-ID: <4F7C9893.1030704@wwwdotorg.org>
References: <1333148404-17691-1-git-send-email-swarren@wwwdotorg.org> <1333148404-17691-4-git-send-email-swarren@wwwdotorg.org> <20120404175722.GC29919@quad.lixom.net>
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To: Olof Johansson <olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org>
Cc: Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>, Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
List-Id: linux-tegra@vger.kernel.org

On 04/04/2012 11:57 AM, Olof Johansson wrote:
> On Fri, Mar 30, 2012 at 04:59:56PM -0600, Stephen Warren wrote:
>> From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>>
>> Tegra20 and Tegra30 share the same register layout within registers, but
>> the addresses of the registers is a little different. Fix the driver to
>> cope with this.
>>
>> @@ -333,6 +336,26 @@ static struct irq_chip tegra_gpio_irq_chip = {
>>  #endif
>>  };
>>  
>> +struct tegra_gpio_soc_config {
>> +	u32 bank_stride;
>> +	u32 upper_offset;
>> +};
>> +
>> +static struct tegra_gpio_soc_config tegra20_gpio_config = {
>> +	.bank_stride = 0x80,
>> +	.upper_offset = 0x800,
>> +};
>> +
>> +static struct tegra_gpio_soc_config tegra30_gpio_config = {
>> +	.bank_stride = 0x100,
>> +	.upper_offset = 0x80,
>> +};
> 
> Hmm. I wonder if this would be better to just describe in the device tree
> bindings for the gpio controller? Perhaps split the reg property in a higher
> and lower to take care of the offset, and add a nvidia,bank-stride=<x>
> property?

Splitting the reg property in two wouldn't really work. Notice that on
Tegra20, bank_stride is less than upper_offset whereas on Tegra30,
bank_stride is larger than upper_offset, so the issue is that in one
case the registers are interleaved and in the other in separate chunks.

I guess we could put those values into DT, but they only vary per SoC
not per board, so there didn't seem much need.

I believe the Tegra30 register layout is applicable to future chips if
it matters.