linux-kernel - Re: [PATCH 13/14] Blackfin SPI driver: Move cs_chg_udelay to cs_deactive to fix bug when some SPI LCD driver needs delay after cs

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Date:	Wed, 31 Oct 2007 12:04:11 -0700
From:	Cameron Barfield <cbarfield@...erdata.net>
To:	bryan.wu@...log.com
CC:	David Brownell <david-b@...bell.net>,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/14] Blackfin SPI driver: Move cs_chg_udelay to	cs_deactive
 to fix bug when some SPI LCD driver needs delay after	cs_deactive

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It may be hardware specific for our board, but my thought is that any device should be
able to take advantage of the cs_chg_udelay regardless of which write function it uses.

As far as I can see, there is no where else to make a clean change to allow devices that
use the "normal" write function the ability to take advantage of cs_chg_udelay.



Bryan Wu wrote:
> On Tue, 2007-10-30 at 13:18 -0700, David Brownell wrote:
>> On Tuesday 30 October 2007, Bryan Wu wrote:
>>> @@ -211,6 +211,10 @@ static void cs_deactive(struct driver_data *drv_data, struct chip_data *chip)
>>>         flag |= (chip->flag << 8);
>>>  
>>>         write_FLAG(drv_data, flag);
>>> +
>>> +       /* Move delay here for consistency */
>>> +       if (chip->cs_chg_udelay)
>>> +               udelay(chip->cs_chg_udelay);
>>>  }
>>>  
>> By the way, if this is something needed very often, that mechanism
>> should be moved into the SPI framework.  It wouldn't be polite if
>> such LCD drivers could only work on Blackfin boards.  :)
> 
> I am not sure whether this LCD needs cs_chg_udelay on other boards.
> It is found by Cameron Barfield. Maybe it is some timing requirement for
> specific hardware.
> 
> -Bryan Wu
> 
> 

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