linux-kernel - Re: [PATCH v4 0/7] i2c: designware: Improve support of multi-messages transfer

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Message-ID: <20251128071908.GA2580184@black.igk.intel.com>
Date: Fri, 28 Nov 2025 08:19:08 +0100
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Benoît Monin <benoit.monin@...tlin.com>
Cc: Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Jan Dabros <jsd@...ihalf.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Gregory CLEMENT <gregory.clement@...tlin.com>,
	Théo Lebrun <theo.lebrun@...tlin.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
	Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
	Dmitry Guzman <dmitry.guzman@...ileye.com>,
	linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH v4 0/7] i2c: designware: Improve support of
 multi-messages transfer

Hi,

On Wed, Nov 26, 2025 at 11:46:23AM +0100, Benoît Monin wrote:
> Add support for the I2C_M_STOP flag to the .xfer() function of the
> designware driver. This allows grouping multiple accesses in a single
> call and changing the target address after a STOP flag. This is achieved
> by splitting i2c_dw_xfer() in two functions. The core logic handling
> the transaction is now in __i2c_dw_xfer_one_part(), while i2c_dw_xfer()
> loops over the messages to search for the I2C_M_STOP flag and calls
> __i2c_dw_xfer_one_part().
> 
> Handle controllers that lack the ability to emit a RESTART when two
> consecutive messages have the same address and direction by aborting
> transfers that contain such a sequence of messages. For those controllers,
> we also check that we do not get any unwanted STOP caused by a Tx FIFO
> underrun, as they lack the ability to hold the clock during a transaction.
> And we set the irq as non-threaded to prevent underrun on PREEMPT-RT
> kernel when filling the FIFO.
> 
> The I2C controllers found in the EyeQ6Lplus and EyeQ7H SoCs from Mobileye
> lack such capability, so a compatible string is added because this cannot
> be detected at runtime.
> 
> This patch series also brings four cleanups:
> * Optimize the read of the message flags in i2c_dw_read().
> * Sort the compatible strings alphabetically in dw_i2c_of_match[].
> * Simplify runtime PM handling in i2c_dw_xfer() with guard.
> * Add a dedicated i2c_algorithm for AMD NAVI controller.
> 
> Signed-off-by: Benoît Monin <benoit.monin@...tlin.com>

All look good to me now, thanks! I also checked that this did not break
anything -> my laptop I2C connected touchscreen & touchpad still works.

For the series,

Acked-by: Mika Westerberg <mika.westerberg@...ux.intel.com>