netdev - Re: [PATCH v2 2/3] net: can: c_can: Add syscon/regmap RAMINIT mechanism

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Date:	Wed, 1 Oct 2014 11:45:51 +0300
From:	Roger Quadros <rogerq@...com>
To:	Marc Kleine-Budde <mkl@...gutronix.de>,
	Wolfram Sang <wsa@...-dreams.de>
CC:	<wg@...ndegger.com>, <tony@...mide.com>, <tglx@...utronix.de>,
	<mugunthanvnm@...com>, <george.cherian@...com>, <balbi@...com>,
	<nsekhar@...com>, <nm@...com>,
	<sergei.shtylyov@...entembedded.com>, <linux-omap@...r.kernel.org>,
	<linux-can@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] net: can: c_can: Add syscon/regmap RAMINIT mechanism

On 09/30/2014 07:04 PM, Marc Kleine-Budde wrote:
> On 09/30/2014 05:25 PM, Wolfram Sang wrote:
>>
>>> Yes, but syscon_regmap_lookup_by_phandle() doesn't need any support for
>>> additional parameters. Have a look at:
>>>
>>> drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
>>>
>>> First get the regmap, then the 1st argument is the offset in the regmap,
>>> the 2nd and 3rd could be the bits.
>>
>> So, for one driver the extra arguments are: <reg> <start_bit> <stop_bit>
>> For another driver (the stmmac example): <reg_offset> <reg_shift>
> 
> The DCAN's "reg" is a "reg_offset" as in the stmmc.
> 
> Roger, can we derive both start and done bit from a common reg_shift?

I'm sorry I didn't understand what you meant.

<&syscon_phandl> <reg offset> <start bit> <stop bit> should work well for us.
Even though reg offset is the same for both the DCAN instances.

> 
>> Phew... Then we should really have a "syscon-raminit" property probably,
>> so that at least plain "syscon" has a consistent syntax?
> 
> I think^whope we can have the same syntax as the stmmc :D

I agree too.

> 
>>>> So, I'd rather drop additional arguments.
>>>>
>>>> Why would you like to have it encoded in DT?
>>>
>>> Where put the information then? Into the driver, but where do you get
>>> the reference which instance of the DCAN you are, so that you can look
>>> up the correct bits?
>>
>> Agreed. I thought we had this information in the driver already, but we
>> haven't...
>>
> 
> The current driver relies on the of_alias_get_id(), which isn't
> considered best practice, is it? So I want to avoid this when switching
> to syscon.

cheers,
-roger
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