Re: [PATCH 4/5] usb: typec: ucsi_acpi: Refactor and fix DELL quirk

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Wed, Mar 20, 2024 at 08:39:25AM +0100, Christian A. Ehrhardt wrote:
> Some DELL systems don't like UCSI_ACK_CC_CI commands with the
> UCSI_ACK_CONNECTOR_CHANGE but not the UCSI_ACK_COMMAND_COMPLETE
> bit set. The current quirk still leaves room for races because
> it requires two consecutive ACK commands to be sent.
> 
> Refactor and significantly simplify the quirk to fix this:
> Send a dummy command and bundle the connector change ack with the
> command completion ack in a single UCSI_ACK_CC_CI command.
> This removes the need to probe for the quirk.
> 
> While there define flag bits for struct ucsi_acpi->flags in ucsi_acpi.c
> and don't re-use definitions from ucsi.h for struct ucsi->flags.
> 
> Fixes: f3be347ea42d ("usb: ucsi_acpi: Quirk to ack a connector change ack cmd")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christian A. Ehrhardt <lk@c--e.de>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/ucsi/ucsi_acpi.c | 75 +++++++++++++-----------------
>  1 file changed, 33 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi_acpi.c b/drivers/usb/typec/ucsi/ucsi_acpi.c
> index 928eacbeb21a..7b3ac133ef86 100644
> --- a/drivers/usb/typec/ucsi/ucsi_acpi.c
> +++ b/drivers/usb/typec/ucsi/ucsi_acpi.c
> @@ -23,10 +23,11 @@ struct ucsi_acpi {
>  	void *base;
>  	struct completion complete;
>  	unsigned long flags;
> +#define UCSI_ACPI_SUPPRESS_EVENT	0
> +#define UCSI_ACPI_COMMAND_PENDING	1
> +#define UCSI_ACPI_ACK_PENDING		2
>  	guid_t guid;
>  	u64 cmd;
> -	bool dell_quirk_probed;
> -	bool dell_quirk_active;
>  };
>  
>  static int ucsi_acpi_dsm(struct ucsi_acpi *ua, int func)
> @@ -79,9 +80,9 @@ static int ucsi_acpi_sync_write(struct ucsi *ucsi, unsigned int offset,
>  	int ret;
>  
>  	if (ack)
> -		set_bit(ACK_PENDING, &ua->flags);
> +		set_bit(UCSI_ACPI_ACK_PENDING, &ua->flags);
>  	else
> -		set_bit(COMMAND_PENDING, &ua->flags);
> +		set_bit(UCSI_ACPI_COMMAND_PENDING, &ua->flags);
>  
>  	ret = ucsi_acpi_async_write(ucsi, offset, val, val_len);
>  	if (ret)
> @@ -92,9 +93,9 @@ static int ucsi_acpi_sync_write(struct ucsi *ucsi, unsigned int offset,
>  
>  out_clear_bit:
>  	if (ack)
> -		clear_bit(ACK_PENDING, &ua->flags);
> +		clear_bit(UCSI_ACPI_ACK_PENDING, &ua->flags);
>  	else
> -		clear_bit(COMMAND_PENDING, &ua->flags);
> +		clear_bit(UCSI_ACPI_COMMAND_PENDING, &ua->flags);
>  
>  	return ret;
>  }
> @@ -129,51 +130,40 @@ static const struct ucsi_operations ucsi_zenbook_ops = {
>  };
>  
>  /*
> - * Some Dell laptops expect that an ACK command with the
> - * UCSI_ACK_CONNECTOR_CHANGE bit set is followed by a (separate)
> - * ACK command that only has the UCSI_ACK_COMMAND_COMPLETE bit set.
> - * If this is not done events are not delivered to OSPM and
> - * subsequent commands will timeout.
> + * Some Dell laptops don't like ACK commands with the
> + * UCSI_ACK_CONNECTOR_CHANGE but not the UCSI_ACK_COMMAND_COMPLETE
> + * bit set. To work around this send a dummy command and bundle the
> + * UCSI_ACK_CONNECTOR_CHANGE with the UCSI_ACK_COMMAND_COMPLETE
> + * for the dummy command.
>   */
>  static int
>  ucsi_dell_sync_write(struct ucsi *ucsi, unsigned int offset,
>  		     const void *val, size_t val_len)
>  {
>  	struct ucsi_acpi *ua = ucsi_get_drvdata(ucsi);
> -	u64 cmd = *(u64 *)val, ack = 0;
> +	u64 cmd = *(u64 *)val;
> +	u64 dummycmd = UCSI_GET_CAPABILITY;
>  	int ret;
>  
> -	if (UCSI_COMMAND(cmd) == UCSI_ACK_CC_CI &&
> -	    cmd & UCSI_ACK_CONNECTOR_CHANGE)
> -		ack = UCSI_ACK_CC_CI | UCSI_ACK_COMMAND_COMPLETE;
> -
> -	ret = ucsi_acpi_sync_write(ucsi, offset, val, val_len);
> -	if (ret != 0)
> -		return ret;
> -	if (ack == 0)
> -		return ret;
> -
> -	if (!ua->dell_quirk_probed) {
> -		ua->dell_quirk_probed = true;
> -
> -		cmd = UCSI_GET_CAPABILITY;
> -		ret = ucsi_acpi_sync_write(ucsi, UCSI_CONTROL, &cmd,
> -					   sizeof(cmd));
> -		if (ret == 0)
> -			return ucsi_acpi_sync_write(ucsi, UCSI_CONTROL,
> -						    &ack, sizeof(ack));
> -		if (ret != -ETIMEDOUT)
> +	if (cmd == (UCSI_ACK_CC_CI | UCSI_ACK_CONNECTOR_CHANGE)) {
> +		cmd |= UCSI_ACK_COMMAND_COMPLETE;
> +
> +		/*
> +		 * The UCSI core thinks it is sending a connector change ack
> +		 * and will accept new connector change events. We don't want
> +		 * this to happen for the dummy command as its response will
> +		 * still report the very event that the core is trying to clear.
> +		 */
> +		set_bit(UCSI_ACPI_SUPPRESS_EVENT, &ua->flags);
> +		ret = ucsi_acpi_sync_write(ucsi, UCSI_CONTROL, &dummycmd,
> +					   sizeof(dummycmd));
> +		clear_bit(UCSI_ACPI_SUPPRESS_EVENT, &ua->flags);
> +
> +		if (ret < 0)
>  			return ret;
> -
> -		ua->dell_quirk_active = true;
> -		dev_err(ua->dev, "Firmware bug: Additional ACK required after ACKing a connector change.\n");
> -		dev_err(ua->dev, "Firmware bug: Enabling workaround\n");
>  	}
>  
> -	if (!ua->dell_quirk_active)
> -		return ret;
> -
> -	return ucsi_acpi_sync_write(ucsi, UCSI_CONTROL, &ack, sizeof(ack));
> +	return ucsi_acpi_sync_write(ucsi, UCSI_CONTROL, &cmd, sizeof(cmd));
>  }
>  
>  static const struct ucsi_operations ucsi_dell_ops = {
> @@ -209,13 +199,14 @@ static void ucsi_acpi_notify(acpi_handle handle, u32 event, void *data)
>  	if (ret)
>  		return;
>  
> -	if (UCSI_CCI_CONNECTOR(cci))
> +	if (UCSI_CCI_CONNECTOR(cci) &&
> +	    !test_bit(UCSI_ACPI_SUPPRESS_EVENT, &ua->flags))
>  		ucsi_connector_change(ua->ucsi, UCSI_CCI_CONNECTOR(cci));
>  
>  	if (cci & UCSI_CCI_ACK_COMPLETE && test_bit(ACK_PENDING, &ua->flags))
>  		complete(&ua->complete);
>  	if (cci & UCSI_CCI_COMMAND_COMPLETE &&
> -	    test_bit(COMMAND_PENDING, &ua->flags))
> +	    test_bit(UCSI_ACPI_COMMAND_PENDING, &ua->flags))
>  		complete(&ua->complete);
>  }
>  
> -- 
> 2.40.1

-- 
heikki