linux-kernel - Re: [PATCH] rtc: omap: Support scratch registers

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Date:   Wed, 8 Nov 2017 08:16:12 +0100
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Keerthy <j-keerthy@...com>
Cc:     Sekhar Nori <nsekhar@...com>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linux OMAP List <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] rtc: omap: Support scratch registers

On 08/11/2017 at 12:38:05 +0530, Keerthy wrote:
> 
> 
> On Wednesday 08 November 2017 11:57 AM, Alexandre Belloni wrote:
> > Hi,
> > 
> > On 08/11/2017 at 11:30:45 +0530, Keerthy wrote:
> >>>>> +static int omap_rtc_scratch_read(void *priv, unsigned int offset, void *_val,
> >>>>> +				 size_t bytes)
> >>>>> +{
> >>>>> +	struct omap_rtc	*rtc = priv;
> >>>>> +	u32 *val = _val;
> >>>>> +	int i;
> >>>>> +
> >>>>> +	for (i = 0; i < bytes / 4; i++)
> >>>>> +		val[i] = rtc_readl(rtc,
> >>>>> +				   OMAP_RTC_SCRATCH0_REG + offset + (i * 4));
> >>
> >> Can the offset be the Scratch register number instead of bytes offset?
> >> More intuitive to me.
> >>
> >> So that one can request using offset as 0, 1, 2 instead of 0, 4, 8?
> >>
> > 
> > Well, the offset is coming from the nvmem core, itself getting it from
> > the Linux file API (and it is in bytes). However, you have the guarantee
> > that it will be aligned on a word, see:
> > http://elixir.free-electrons.com/linux/latest/source/drivers/nvmem/core.c#L88
> 
> Okay Alexandre. Thanks for clarifying. Looks good to me.
> I have tested on AM437X-GP-EVM.
> 

If needed, you can define nvmem cells (and I guess that is what you
want):
http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/nvmem/nvmem.txt


-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com