linux-kernel - Re: [PATCH 15/36] ARM: OMAP2+: gpmc: Allow drivers to query GPMC

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Message-ID: <539AACB9.5080105@ti.com>
Date:	Fri, 13 Jun 2014 10:48:09 +0300
From:	Roger Quadros <rogerq@...com>
To:	Tony Lindgren <tony@...mide.com>
CC:	<dwmw2@...radead.org>, <computersforpeace@...il.com>,
	<kyungmin.park@...sung.com>, <pekon@...com>,
	<ezequiel.garcia@...e-electrons.com>, <javier@...hile0.org>,
	<nsekhar@...com>, <linux-omap@...r.kernel.org>,
	<linux-mtd@...ts.infradead.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 15/36] ARM: OMAP2+: gpmc: Allow drivers to query GPMC_CLK
 period

On 06/13/2014 10:26 AM, Tony Lindgren wrote:
> * Roger Quadros <rogerq@...com> [140611 01:59]:
>> GPMC_CLK is the external clock output pin that is used for syncronous
>> accesses.
>>
>> Device drivers need to know the fastest possible GPMC_CLK period in order
>> to calculate the most optimal device timings. Add the function
>> omap_gpmc_get_clk_period() to allow drivers to get the nearset possible
>> (equal to or greater than) GPMC_CLK period given the minimum
>> clock period supported by the attached device.
>>
>> This is especially needed by the onenand driver as it calculates
>> device timings on the fly for various onenand speed grades.
> 
> Here too this should probably still be done by the gpmc to driver
> glue layer, not by the actual driver that shoud be Linux generic.

Well, this is only needed by the omap-onenand driver to perform the timing calculations at run-time.
Other option is to model the GPMC_CLK (external) as a clock and request the rate using the clock framework.
But since this and the retime() is only used by 2 OMAP specific drivers, I'm not sure if it is worth the effort.

cheers,
-roger

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