linux-kernel - Re: [PATCH v2 3/3] usb: typec: ucsi_glink: drop special handling for CCI

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Date: Tue, 9 Apr 2024 21:26:25 +0200
From: "Christian A. Ehrhardt" <lk@...e.de>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 3/3] usb: typec: ucsi_glink: drop special handling for
 CCI_BUSY


Hi Dmitry,

On Tue, Apr 09, 2024 at 06:29:18PM +0300, Dmitry Baryshkov wrote:
> Newer Qualcomm platforms (sm8450+) successfully handle busy state and
> send the Command Completion after sending the Busy state. Older devices
> have firmware bug and can not continue after sending the CCI_BUSY state,
> but the command that leads to CCI_BUSY is already forbidden by the
> NO_PARTNER_PDOS quirk.
> 
> Follow other UCSI glue drivers and drop special handling for CCI_BUSY
> event. Let the UCSI core properly handle this state.
> 
> Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>  drivers/usb/typec/ucsi/ucsi_glink.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi_glink.c b/drivers/usb/typec/ucsi/ucsi_glink.c
> index 9ffea20020e7..fe9b951f5228 100644
> --- a/drivers/usb/typec/ucsi/ucsi_glink.c
> +++ b/drivers/usb/typec/ucsi/ucsi_glink.c
> @@ -176,7 +176,8 @@ static int pmic_glink_ucsi_sync_write(struct ucsi *__ucsi, unsigned int offset,
>  	left = wait_for_completion_timeout(&ucsi->sync_ack, 5 * HZ);
>  	if (!left) {
>  		dev_err(ucsi->dev, "timeout waiting for UCSI sync write response\n");
> -		ret = -ETIMEDOUT;
> +		/* return 0 here and let core UCSI code handle the CCI_BUSY */
> +		ret = 0;
>  	} else if (ucsi->sync_val) {
>  		dev_err(ucsi->dev, "sync write returned: %d\n", ucsi->sync_val);
>  	}
> @@ -243,11 +244,8 @@ static void pmic_glink_ucsi_notify(struct work_struct *work)
>  		ucsi_connector_change(ucsi->ucsi, con_num);
>  	}
>  
> -	if (ucsi->sync_pending && cci & UCSI_CCI_BUSY) {
> -		ucsi->sync_val = -EBUSY;
> -		complete(&ucsi->sync_ack);
> -	} else if (ucsi->sync_pending &&
> -		   (cci & (UCSI_CCI_ACK_COMPLETE | UCSI_CCI_COMMAND_COMPLETE))) {
> +	if (ucsi->sync_pending &&
> +	    (cci & (UCSI_CCI_ACK_COMPLETE | UCSI_CCI_COMMAND_COMPLETE))) {
>  		complete(&ucsi->sync_ack);
>  	}
>  }

This handling of the command completion turned out to be racy in
the ACPI case: If a normal command was sent one should wait for
UCSI_CCI_COMMAND_COMPLETE only. In case of an UCSI_ACK_CC_CI
command the completion is indicated by UCSI_CCI_ACK_COMPLETE.

While not directly related, a port of this 
    https://lore.kernel.org/all/20240121204123.275441-3-lk@c--e.de/
would nicely fit into this series.

I don't have the hardware to do this myself.


Best regards,
Christian