Re: [PATCH v2 0/6] i2c: send STOP after recovery; use it for i2c-rcar

[Wolfram Sang <wsa@the-dreams.de>]

[-- Attachment #1: Type: text/plain, Size: 2269 bytes --]

On Tue, Jan 09, 2018 at 02:58:53PM +0100, Wolfram Sang wrote:
> From: Wolfram Sang <wsa+renesas@sang-engineering.com>
> 
> When implementing bus recovery for the i2c-rcar driver, two problems were
> encountered: 1) When reading the SDA bit, not the SDA status was returned but
> the internal state of the "bus_is_busy" logic. 2) This logic needs a STOP to
> consider the bus free again. SCL/SDA high is not enough, and there is no other
> way known to reset the internal logic otherwise.
> 
> The obvious solution to just send STOP after recovery makes sense for the
> generic case, too, IMO. If we made a device release SDA again, and are about
> start a new transfer using START, then we should terminate the previous state
> properly with STOP. This may help with some devices and shouldn't create any
> drawback AFAICS.
> 
> For this, we need to introduce a 'set_sda' callback to the recovery
> infrastructure. The first five patches may be interesting for anyone, so input
> is greatly appreciated. Also, testing the new features with GPIO based recovery
> would be awesome to have. Thanks to Phil for testing already!
> 
> This was tested on a Renesas Lager board (r8a7790/R-Car H2). My test procedure
> is documented here:
> 
> https://elinux.org/Tests:I2C-bus-recovery
> 
> A branch is available here:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/rcar-i2c-recovery
> 
> Please let me know what you think.
> 
> Changes since V1:
> 
> * add more identifiers in patch 2
> * don't use GPIOF_* flags but hardocded '0'
> * added Phil's Tested-by
> 
> 
> 
> Wolfram Sang (6):
>   i2c: make kerneldoc about bus recovery more precise
>   i2c: add identifier in declarations for i2c_bus_recovery
>   i2c: add 'set_sda' to bus_recovery_info
>   i2c: ensure SDA is released in recovery if SDA is controllable
>   i2c: send STOP after successful bus recovery
>   i2c: rcar: implement bus recovery
> 
>  drivers/i2c/busses/i2c-rcar.c | 54 +++++++++++++++++++++++++++++++++++++++++--
>  drivers/i2c/i2c-core-base.c   | 25 +++++++++++++++++++-
>  include/linux/i2c.h           | 26 ++++++++++++---------
>  3 files changed, 91 insertions(+), 14 deletions(-)

Applied to for-next, thanks!


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]