linux-kernel - Re: [PATCH 00/12] i2c: core: introduce atomic transfers

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Date:   Wed, 3 Apr 2019 16:15:10 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc:     linux-i2c@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Peter Rosin <peda@...ntia.se>,
        Stefan Lengfeld <contact@...fanchrist.eu>,
        linux-omap@...r.kernel.org, linux-tegra@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 00/12] i2c: core: introduce atomic transfers

On Wed, Apr 03, 2019 at 02:40:07PM +0200, Wolfram Sang wrote:
> This series adds support for very late atomic transfers to the I2C subsystem.
> It finally reached a state which I think is ready-to-apply. This is mainly
> because of two things:
> 
> a) we decided to respect the current locking scheme and to not give atomic
> transfers a priority. The code needed for that would have been either
> incomplete or very invasive. And we cannot guarantee successful transfers
> anyhow. See [1] for the discussion and other write-ups for design choices.
> 
> b) thanks to a discussion with Peter Zijlstra[2], the conditions when to allow
> atomic transfers became much clearer. The new helper i2c_in_atomic_xfer_mode()
> adds readability, too.
> 
> In detail, changes since RFC v2:
> 
> * dropped coding style patch because already applied
> * added new patch 1 to drop in_atomic() and have better conditions when
>   to enter the atomic path
> * added support to the mux-core
> * simplified omap conversion a little
> * added new conversions for ocores, stu300, and algo-bit/gpio
> * typo corrections found by Simon and Stefan
> * added tags to drivers
> * dropped tags from core patches because that part changed too much
> 
> All tested on a Renesas Lager board (R-Car H2). Sadly, the i2c-sh_mobile driver
> cannot be converted now because of other work needed first. I tested with the
> i2c-gpio driver, though. The other driver patches are build tested. A branch
> can be found here:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/i2c/atomic_xfer
> 
> I am happy for reviews and comments. Please note if you review (especially the
> core parts), I'd like to have a short summary of your review even if there is
> no proposed change. Like what you did, what you think about it, etc. Some stuff
> in here is subtle, so if you went through the effort to double check my
> assumptions you should name it :)
> 

Thank you!

FWIW,

Reviewed-by Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

for patches 1-5,12.

Indeed, atomic condition sounds clear now.

> 
> Finally, a big thank you and credit to Renesas for funding this work, of course!
> 
> Happy hacking,
> 
>    Wolfram
> 
> [1] https://lkml.org/lkml/2019/3/2/76
> [2] http://patchwork.ozlabs.org/patch/1067437/
> 
> Wolfram Sang (12):
>   i2c: remove use of in_atomic()
>   i2c: core: use I2C locking behaviour also for SMBUS
>   i2c: core: introduce callbacks for atomic transfers
>   i2c: mux: populate the new *_atomic callbacks
>   i2c: demux: handle the new atomic callbacks
>   i2c: omap: Add the master_xfer_irqless hook
>   i2c: tegra-bpmp: convert to use new atomic callbacks
>   i2c: ocores: refactor setup for polling
>   i2c: ocores: enable atomic xfers
>   i2c: stu300: use xfer_atomic callback to bail out early
>   i2c: algo: bit: add flag to whitelist atomic transfers
>   i2c: gpio: flag atomic capability if possible
> 
>  drivers/i2c/algos/i2c-algo-bit.c      | 22 +++++++++-
>  drivers/i2c/busses/i2c-gpio.c         |  2 +
>  drivers/i2c/busses/i2c-ocores.c       | 16 +++-----
>  drivers/i2c/busses/i2c-omap.c         | 76 +++++++++++++++++++++++++++++------
>  drivers/i2c/busses/i2c-stu300.c       | 25 +++++-------
>  drivers/i2c/busses/i2c-tegra-bpmp.c   | 25 +++++++++---
>  drivers/i2c/i2c-core-base.c           | 17 ++++----
>  drivers/i2c/i2c-core-smbus.c          | 25 +++++++++---
>  drivers/i2c/i2c-core.h                | 25 ++++++++++++
>  drivers/i2c/i2c-mux.c                 |  6 +++
>  drivers/i2c/muxes/i2c-demux-pinctrl.c |  2 +
>  include/linux/i2c-algo-bit.h          |  1 +
>  include/linux/i2c.h                   | 15 +++++--
>  13 files changed, 194 insertions(+), 63 deletions(-)
> 
> -- 
> 2.11.0
> 

-- 
With Best Regards,
Andy Shevchenko