Re: [PATCH v3 7/9] platform/chrome: of_hw_prober: Add delay for hana trackpads

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Jul 21, 2026 at 03:52:21PM +0800, Chen-Yu Tsai wrote:
> Up until now, the MT8173 elm/hana device tree has set the dedicated
> regulator supplying the trackpad as always-on, simply because the Elan
> driver was missing proper delays. As a result the delay for the
> Synaptics trackpad was also omitted, as it was not strictly required
> under such a model and delayed the availability of the trackpad to the
> user.
> 
> The Elan driver recently gained proper delays after power-up, with
> adaptive skipping of the delay if the regulator was originally
> on. The I2C HID driver and I2C OF component prober library gained
> similar adaptive delay skipping. The device tree will be fixed to have
> the regulator not be always on, and proper post-power-on delay time
> added to the I2C HID device.
> 
> Also add the post-power-on delay to the ChromeOS OF component prober,
> so that if the regulator is off at the time of probing, the prober knows
> to wait for the hardware to initialize.

...

> +++ b/drivers/platform/chrome/chromeos_of_hw_prober.c

>  		/*
>  		 * ELAN trackpad needs 2 ms for H/W init and 100 ms for F/W init.
>  		 * Synaptics trackpad needs 100 ms.
> -		 * However, the regulator is set to "always-on", presumably to
> -		 * avoid this delay. The ELAN driver is also missing delays.
>  		 */
> -		.post_power_on_delay_ms = 0,
> +		.post_power_on_delay_ms = 110,

This and the other delay in the previous patches are all HW-related. What if
another touchpad gets connected? I mean that the delays for the certain HW
should not affect other possible devices connected to the platform.

-- 
With Best Regards,
Andy Shevchenko