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

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Message-ID: <fbb305e3-73b3-7a2d-99cf-a7205b7344ff@roeck-us.net>
Date:   Mon, 28 Feb 2022 05:57:27 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Zev Weiss <zev@...ilderbeest.net>, linux-i2c@...r.kernel.org,
        Peter Rosin <peda@...ntia.se>, Rob Herring <robh+dt@...nel.org>
Cc:     openbmc@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/2] ic2: mux: pca9541: add delayed-release support

On 2/28/22 00:43, Zev Weiss wrote:
> On Mon, Jan 31, 2022 at 04:18:08PM PST, Zev Weiss wrote:
>> 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).
>>
> 
> Ping...Guenter, any thoughts on this?
> 

It sounds reasonable to me, but I don't have access to hardware anymore
to test it, so I have no means to confirm that it actually works.

Guenter