linux-kernel - Re: [PATCH] platform/chrome: cros_ec_typec: deferred probe when typec count mismatch

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Date:   Wed, 21 Dec 2022 10:58:32 +0800
From:   Ruihai Zhou <zhouruihai@...qin.corp-partner.google.com>
To:     pmalani@...omium.org, bleung@...omium.org, groeck@...omium.org,
        knoxchiou@...omium.org, weishunc@...omium.org
Cc:     chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/chrome: cros_ec_typec: deferred probe when typec count mismatch

> I think that is problematic. It might as well be that nports >
> EC_USB_PD_MAX_PORTS.
Yes, you're right. so we should consider it's a invalid argument and return -EINVAL
if nports > EC_USB_PD_MAX_PORTS. right?
> Is this really seen in the field ? The EC should never report a wrong
> (random) number of ports. If it is not ready, there should be _some_
> indication that it isn't ready. Does it really report a more or less
> random number in this case ?
Yes, I saw this on corsola boards. The EC report a wrong(not random) number.
because corsola emulates HDMI MUX over the current type-c mux stack. The ec has to
fake a type-c port to pass the MUX info. But the task are not initiated on starting up,
and increase the type-c port counts after the tasks finished. In this case, I saw
the typec->num_ports = 1, but the nports = 2, which will be probe failed and block
the HDMI MUX function.
I will send v2 patch, if nports > EC_USB_PD_MAX_PORTS, then return -EINVAL,
but if nports > typec->num_ports, we consider wait a second to ec task increase the
type-c port counts if there're HDMI DB attach, then return -EPROBE_DEFER.