Re: [PATCH v2 04/15] HID: ft260: i2c: reduce driver module loading time

[sashiko-bot@kernel.org]

> The HWMON class I2C client drivers register the address range to scan
> during the I2C master module probing. For example, the lm75 module
> registers eight bus addresses scanned during the ft260 module loading.
> 
> In the case of ft260, the bus is scanned by ft260_i2c_read, but due to
> an excessive read completion timeout, it took about 40 seconds for the
> ft260 driver to scan the lm75 address range before exiting the probe
> function.
> 
> Adjust the i2c_read timeout so it depends on the amount of data to
> read, reducing the lm75 address range scan time to about 200ms.
> 
> The 25 ms per-report budget was checked on a UMFT260EV1A with a 24LC512
> EEPROM by shrinking the timeout until reads began to fail: a 60-byte
> read still completes at 9 ms and times out at 7 ms, against 5.4 ms of
> wire time at 100 kHz, so the fixed USB, HID and scheduling overhead
> costs a few milliseconds. At the chip's slowest 60 kHz clock that chunk
> needs about 9 ms on the wire and a 180-byte chunk about 27 ms. Scale
> the wait by 25 ms per 60-byte HID payload so a last chunk of 61..180
> bytes gets 50..75 ms, not the single-report 25 ms budget (reported by
> Sashiko).
> 
> Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261030223637.86907-1-michael.zaidman@gmail.com?part=4