linux-kernel - Re: [RFC] Fix stuck UCSI controller on DELL

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Message-ID: <34101c32-65cd-4433-974f-23a16f9981fa@amd.com>
Date: Tue, 16 Jan 2024 21:00:03 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: "Christian A. Ehrhardt" <lk@...e.de>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: linux-usb@...r.kernel.org, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Neil Armstrong <neil.armstrong@...aro.org>,
 Hans de Goede <hdegoede@...hat.com>, Saranya Gopal
 <saranya.gopal@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] Fix stuck UCSI controller on DELL

On 1/15/2024 12:55, Christian A. Ehrhardt wrote:
> 
> Hi Heikki,
> 
> sorry to bother you again with this but I'm afraid there's
> a misunderstanding wrt. the nature of the quirk. See below:
> 
> On Thu, Jan 04, 2024 at 01:59:02PM +0200, Heikki Krogerus wrote:
>> Hi Christian,
>>
>> On Wed, Jan 03, 2024 at 11:06:35AM +0100, Christian A. Ehrhardt wrote:
>>> I have a DELL Latitude 5431 where typec only works somewhat.
>>> After the first plug/unplug event the PPM seems to be stuck and
>>> commands end with a timeout (GET_CONNECTOR_STATUS failed (-110)).
>>>
>>> This patch fixes it for me but according to my reading it is in
>>> violation of the UCSI spec. On the other hand searching through
>>> the net it appears that many DELL models seem to have timeout problems
>>> with UCSI.
>>>
>>> Do we want some kind of quirk here? There does not seem to be a quirk
>>> framework for this part of the code, yet. Or is it ok to just send the
>>> additional ACK in all cases and hope that the PPM will do the right
>>> thing?
>>
>> We can use DMI quirks. Something like the attached diff (not tested).
>>
>> thanks,
>>
>> -- 
>> heikki
> 
>> diff --git a/drivers/usb/typec/ucsi/ucsi_acpi.c b/drivers/usb/typec/ucsi/ucsi_acpi.c
>> index 6bbf490ac401..7e8b1fcfa024 100644
>> --- a/drivers/usb/typec/ucsi/ucsi_acpi.c
>> +++ b/drivers/usb/typec/ucsi/ucsi_acpi.c
>> @@ -113,18 +113,44 @@ ucsi_zenbook_read(struct ucsi *ucsi, unsigned int offset, void *val, size_t val_
>>   	return 0;
>>   }
>>   
>> -static const struct ucsi_operations ucsi_zenbook_ops = {
>> -	.read = ucsi_zenbook_read,
>> -	.sync_write = ucsi_acpi_sync_write,
>> -	.async_write = ucsi_acpi_async_write
>> -};
>> +static int ucsi_dell_sync_write(struct ucsi *ucsi, unsigned int offset,
>> +				const void *val, size_t val_len)
>> +{
>> +	u64 ctrl = *(u64 *)val;
>> +	int ret;
>> +
>> +	ret = ucsi_acpi_sync_write(ucsi, offset, val, val_len);
>> +	if (ret && (ctrl & (UCSI_ACK_CC_CI | UCSI_ACK_CONNECTOR_CHANGE))) {
>> +		ctrl= UCSI_ACK_CC_CI | UCSI_ACK_COMMAND_COMPLETE;
>> +
>> +		dev_dbg(ucsi->dev->parent, "%s: ACK failed\n", __func__);
>> +		ret = ucsi_acpi_sync_write(ucsi, UCSI_CONTROL, &ctrl, sizeof(ctrl));
>> +	}
> 
> Unfortunately, this has the logic reversed. The quirk (i.e. the
> additional UCSI_ACK_COMMAND_COMPLETE) is required after a _successful_
> UCSI_ACK_CONNECTOR_CHANGE. Otherwise, _subsequent_ commands will timeout
> (usually the next GET_CONNECTOR_CHANGE).
> 
> This means the quirk must be applied _before_ we detect any failure.
> Consequently, the quirk has the potential to break working systems.
> 
> Sorry, if that wasn't clear from my original mail. Please let me know
> if this changes how you want the quirks handled.
> 
>       Thanks    Christian
> 

For the problematic scenario have you tried to play with it a bit to see 
if it's too short of a timeout (raise timeout) or to output the response 
bits to see if anything else surprising is sent?

Does it always fail on the same command, or does it happen to a bunch of 
them?