linux-kernel - [PATCH 0/2] ic2: mux: pca9541: add delayed-release support

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Date:   Mon, 24 Jan 2022 13:38:48 -0800
From:   Zev Weiss <zev@...ilderbeest.net>
To:     linux-i2c@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Peter Rosin <peda@...ntia.se>, Rob Herring <robh+dt@...nel.org>
Cc:     Zev Weiss <zev@...ilderbeest.net>, openbmc@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: [PATCH 0/2] ic2: mux: pca9541: add delayed-release support

Hello,

This series adds support for a new pca9541 device-tree property
("release-delay-us"), which delays releasing ownership of the bus
after a transaction for a configurable duration, anticipating that
another transaction may follow shortly.  By avoiding a
release/reacquisition between transactions, this can provide a
substantial performance improvement for back-to-back operations -- on
a Delta AHE-50DC (ASPEED AST1250) system running OpenBMC with LM25066
PMICs behind PCA9541-arbitrated busses, a setting of 10000 (10 ms)
reduces the median latency of reading hwmon sysfs files from 2.28 ms
to 0.99 ms (a 57% improvement).

Thanks,
Zev

Zev Weiss (2):
  i2c: mux: pca9541: add delayed-release support
  dt-bindings: i2c: add nxp,pca9541 release-delay-us property

 .../devicetree/bindings/i2c/nxp,pca9541.txt   | 10 ++++
 drivers/i2c/muxes/i2c-mux-pca9541.c           | 56 ++++++++++++++++---
 2 files changed, 57 insertions(+), 9 deletions(-)

-- 
2.34.1