From mboxrd@z Thu Jan 1 00:00:00 1970 From: Murali Karicheri Subject: Re: [PATCH v2] spi: davinci: add support for adding delay between word's transmission Date: Tue, 9 Sep 2014 14:20:27 -0400 Message-ID: <540F44EB.8090700@ti.com> References: <1410278851-10783-1-git-send-email-grygorii.strashko@ti.com> <20140909165555.GD2601@sirena.org.uk> <540F3447.3020609@ti.com> <20140909172057.GH2601@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140909172057.GH2601-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: Errors-To: davinci-linux-open-source-bounces-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org To: Mark Brown Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org, Ian Campbell , linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring , santosh.shilimkar-l0cyMroinI0@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On 09/09/2014 01:20 PM, Mark Brown wrote: > On Tue, Sep 09, 2014 at 01:09:27PM -0400, Murali Karicheri wrote: >> On 09/09/2014 12:55 PM, Mark Brown wrote: >>> On Tue, Sep 09, 2014 at 07:07:31PM +0300, Grygorii Strashko wrote: > >>>> - ti,spi-c2t-delay: Chip-select-active-to-transmit-start delay >>>> (SPIDELAY.C2TDELAY) > >>>> - ti,spi-t2c-delay: Transmit-end-to-chip-select-inactive delay >>>> (SPIDELAY.T2CDELAY) > >>> Now I look at these they look very much like the standard delay feature >>> that the SPI subsystem has already - are they? > >> As Grygorii explained in previous postings (reproduced below), these delays >> are handled by the SPI hardware on Keystone and affect the delay between >> successive word tranmssion and has nothing to do with the delay you are >> talking about. Isn't the standard delay you mention here is between >> successive packets send down to the lower level driver (in this case >> spi-davinci.c) ? > > He talked about such delays between words (and there were some other > delays listed which seemed to meet that description) but the above don't > appear to refer to them, the above refer to delays around chip select > which most definitely are covered with the standard delays. > > If these delays are not related to chip select then the documentation > needs to be fixed to not refer to chip select. Ok. So what I understand is the issue is not having the right description to indicate that these parameters are delays associated with tranmission of successive words on the wire. Personally I like these description match with what is described in the device spec/ user guide and what is described above match with that. However we could add additional description as below to to make it more explicit. spi-c2t-delay - delay after CS is asserted before output bits on wire spi-t2c-delay - delay after tramission of bits and before deasserting CS wdelay - delay between successive word transmission. Do you think this will help? Murali