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

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Message-ID: <542BD116.4090809@pengutronix.de>
Date:	Wed, 01 Oct 2014 12:01:58 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Roger Quadros <rogerq@...com>, 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 10/01/2014 11:06 AM, Roger Quadros wrote:
> On 10/01/2014 11:47 AM, Marc Kleine-Budde wrote:
>> On 10/01/2014 10:45 AM, Roger Quadros wrote:
>>> 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.
>>
>> What's start bit and stop bit for instance 0 and 1 on that SoC that has
>> two instances?
>>
> 
> we have 3 SoCs at the moment, all have 2 DCAN instances.
> 
> AM33xx & AM43xx
> instance	start	stop
> 1		0	8
> 2		1	9	

If we use a 0-based numbering for the instances:
instance	start		stop
0		(0 << instance)	(8 << instance)
1		(0 << instance)	(8 << instance)

> DRA7xx
> instance	start	stop
> 1		3	1
> 2		5	2
                ^
5 or 4?

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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