linux-kernel - Re: [RFC PATCH 0/7] usb: typec: ucsi: Polling the alt modes and PDOs

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Message-ID: <YMIAh1uDgeglJYNN@kuha.fi.intel.com>
Date:   Thu, 10 Jun 2021 15:07:35 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Benjamin Berg <bberg@...hat.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/7] usb: typec: ucsi: Polling the alt modes and PDOs

On Wed, Jun 09, 2021 at 07:39:41PM +0200, Benjamin Berg wrote:
> My thought when I first ran into the issue was that the PPM simply
> resets the change bitfield on ACK, effectively discarding any changes
> that happened after the last GET_CONNECTOR_STATUS call. I believed to
> have confirmed this by inserting an msleep in between.
> However, I have to admit that I have never really looked for
> alternative explanations.

Thanks a lot for testing these. I now have pretty good idea about the
problem. The problem is not what you though it is, but the driver is
also not too slow like I suspected.

I'm quite certain now that the PPM simply does not create the event at
all in this case, regardless of what the driver does. We do need to
workaround that problem, but I think we can do it in a better way. I
have an idea for that.

thanks,

-- 
heikki