linux-kernel - [PATCH v2 0/2] ic2: mux: pca9541: add delayed-release support

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Date:   Mon, 31 Jan 2022 16:18:08 -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 v2 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 dozens
of LM25066 PMICs on PCA9541-arbitrated busses, a setting of 10000 (10
ms) reduces the median latency the psusensor daemon's hwmon sysfs file
reads from 2.28 ms to 0.99 ms (a 57% improvement).

Thanks,
Zev

Changes since v1 [0]:
 - removed spurious #include line from dt-bindings example

[0] https://lore.kernel.org/linux-i2c/20220124213850.3766-1-zev@bewilderbeest.net/

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   |  9 +++
 drivers/i2c/muxes/i2c-mux-pca9541.c           | 56 ++++++++++++++++---
 2 files changed, 56 insertions(+), 9 deletions(-)

-- 
2.34.1