From mboxrd@z Thu Jan 1 00:00:00 1970 From: Santosh Shilimkar Subject: Re: [PATCH v2 5/7] i2c: omap: wait for transfer completion before sending STP bit Date: Thu, 25 Oct 2012 18:31:58 +0530 Message-ID: <50893846.3020106@ti.com> References: <1350899218-13624-1-git-send-email-balbi@ti.com> <1351167915-15079-1-git-send-email-balbi@ti.com> <1351167915-15079-6-git-send-email-balbi@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1351167915-15079-6-git-send-email-balbi-l0cyMroinI0@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Felipe Balbi Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux OMAP Mailing List , Linux ARM Kernel Mailing List , Tony Lindgren , Shubhrajyoti Datta , Benoit Cousson , w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, michael-dyjBcgdgk7Pe9wHmmfpqLFaTQe2KTcn/@public.gmane.org List-Id: linux-i2c@vger.kernel.org On Thursday 25 October 2012 05:55 PM, Felipe Balbi wrote: > Later patches will come adding support for > reporting amount of bytes transferred so that > client drivers can count how many bytes are > left to transfer. > > This is useful mostly in case of NACKs when > client driver wants to know exactly which > byte got NACKed so it doesn't have to resend > all bytes again. > > In order to make that work with OMAP's I2C > controller, we need to prevent sending STP > bit until message is transferred. The reason > behind that is because OMAP_I2C_CNT_REG gets > reset to original value after STP bit is > shifted through I2C_SDA line and that would > prevent us from reading the correct number of > bytes left to transfer. > > The full programming model suggested by IP > owner was the following: > > - start I2C transfer (without STP bit) > - upon completion or NACK, read I2C_CNT register > - write STP bit to I2C_CON register > - wait for ARDY bit > > With this patch we're implementing all steps > except step #2 which will come in a later > patch adding such support. > Will this not break the bisect since CNT and NACK, completion is added in later patch > Signed-off-by: Felipe Balbi > --- Apart from above, rest of the change follow the change log and looks fine tome. The change is quite drastic so hopefully it has gone through wider testing. Regards santosh From mboxrd@z Thu Jan 1 00:00:00 1970 From: santosh.shilimkar@ti.com (Santosh Shilimkar) Date: Thu, 25 Oct 2012 18:31:58 +0530 Subject: [PATCH v2 5/7] i2c: omap: wait for transfer completion before sending STP bit In-Reply-To: <1351167915-15079-6-git-send-email-balbi@ti.com> References: <1350899218-13624-1-git-send-email-balbi@ti.com> <1351167915-15079-1-git-send-email-balbi@ti.com> <1351167915-15079-6-git-send-email-balbi@ti.com> Message-ID: <50893846.3020106@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thursday 25 October 2012 05:55 PM, Felipe Balbi wrote: > Later patches will come adding support for > reporting amount of bytes transferred so that > client drivers can count how many bytes are > left to transfer. > > This is useful mostly in case of NACKs when > client driver wants to know exactly which > byte got NACKed so it doesn't have to resend > all bytes again. > > In order to make that work with OMAP's I2C > controller, we need to prevent sending STP > bit until message is transferred. The reason > behind that is because OMAP_I2C_CNT_REG gets > reset to original value after STP bit is > shifted through I2C_SDA line and that would > prevent us from reading the correct number of > bytes left to transfer. > > The full programming model suggested by IP > owner was the following: > > - start I2C transfer (without STP bit) > - upon completion or NACK, read I2C_CNT register > - write STP bit to I2C_CON register > - wait for ARDY bit > > With this patch we're implementing all steps > except step #2 which will come in a later > patch adding such support. > Will this not break the bisect since CNT and NACK, completion is added in later patch > Signed-off-by: Felipe Balbi > --- Apart from above, rest of the change follow the change log and looks fine tome. The change is quite drastic so hopefully it has gone through wider testing. Regards santosh