[2/3] usb: ucsi_acpi: Fix command completion handling

Commit Message

Christian A. Ehrhardt Jan. 16, 2024, 10:40 p.m. UTC

In case of a spurious or otherwise delayed notification it is
possible that CCI still reports the previous completion. The
UCSI spec is aware of this and provides two completion bits in
CCI, one for normal commands and one for acks. As acks and commands
alternate the notification handler can determine if the completion
bit is from the current command.

The initial UCSI code correctly handled this but the distinction
between the two completion bits was lost with the introduction of
the new API.

To fix this revive the ACK_PENDING bit for ucsi_acpi and only complete
commands if the completion bit matches.

Fixes: f56de278e8ec ("usb: typec: ucsi: acpi: Move to the new API")
Signed-off-by: Christian A. Ehrhardt <[e-mail]>
---
NOTES:
- I've seen real issues as a result of this.
- UCSI implementations other than ACPI might need a similar fix.
  I can give relevant maintainers a heads up once this is properly
  reviewed and integrated.

 drivers/usb/typec/ucsi/ucsi_acpi.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

Comments

Greg Kroah-Hartman Jan. 17, 2024, 5:44 a.m. UTC | #1

On Tue, Jan 16, 2024 at 11:40:40PM +0100, Christian A. Ehrhardt wrote:
> In case of a spurious or otherwise delayed notification it is
> possible that CCI still reports the previous completion. The
> UCSI spec is aware of this and provides two completion bits in
> CCI, one for normal commands and one for acks. As acks and commands
> alternate the notification handler can determine if the completion
> bit is from the current command.
> 
> The initial UCSI code correctly handled this but the distinction
> between the two completion bits was lost with the introduction of
> the new API.
> 
> To fix this revive the ACK_PENDING bit for ucsi_acpi and only complete
> commands if the completion bit matches.
> 
> Fixes: f56de278e8ec ("usb: typec: ucsi: acpi: Move to the new API")
> Signed-off-by: Christian A. Ehrhardt <[e-mail]>
> ---
> NOTES:
> - I've seen real issues as a result of this.
> - UCSI implementations other than ACPI might need a similar fix.
>   I can give relevant maintainers a heads up once this is properly
>   reviewed and integrated.
> 
>  drivers/usb/typec/ucsi/ucsi_acpi.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You have marked a patch with a "Fixes:" tag for a commit that is in an
  older released kernel, yet you do not have a cc: stable line in the
  signed-off-by area at all, which means that the patch will not be
  applied to any older kernel releases.  To properly fix this, please
  follow the documented rules in the
  Documentation/process/stable-kernel-rules.rst file for how to resolve
  this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Patch

diff --git a/drivers/usb/typec/ucsi/ucsi_acpi.c b/drivers/usb/typec/ucsi/ucsi_acpi.c
index 6bbf490ac401..33dac67154d2 100644
--- a/drivers/usb/typec/ucsi/ucsi_acpi.c
+++ b/drivers/usb/typec/ucsi/ucsi_acpi.c
@@ -73,9 +73,13 @@  static int ucsi_acpi_sync_write(struct ucsi *ucsi, unsigned int offset,
 				const void *val, size_t val_len)
 {
 	struct ucsi_acpi *ua = ucsi_get_drvdata(ucsi);
+	bool ack = UCSI_COMMAND(*(u64*)val) == UCSI_ACK_CC_CI;
 	int ret;
 
-	set_bit(COMMAND_PENDING, &ua->flags);
+	if (ack)
+		set_bit(ACK_PENDING, &ua->flags);
+	else
+		set_bit(COMMAND_PENDING, &ua->flags);
 
 	ret = ucsi_acpi_async_write(ucsi, offset, val, val_len);
 	if (ret)
@@ -85,7 +89,10 @@  static int ucsi_acpi_sync_write(struct ucsi *ucsi, unsigned int offset,
 		ret = -ETIMEDOUT;
 
 out_clear_bit:
-	clear_bit(COMMAND_PENDING, &ua->flags);
+	if (ack)
+		clear_bit(ACK_PENDING, &ua->flags);
+	else
+		clear_bit(COMMAND_PENDING, &ua->flags);
 
 	return ret;
 }
@@ -142,8 +149,10 @@  static void ucsi_acpi_notify(acpi_handle handle, u32 event, void *data)
 	if (UCSI_CCI_CONNECTOR(cci))
 		ucsi_connector_change(ua->ucsi, UCSI_CCI_CONNECTOR(cci));
 
-	if (test_bit(COMMAND_PENDING, &ua->flags) &&
-	    cci & (UCSI_CCI_ACK_COMPLETE | UCSI_CCI_COMMAND_COMPLETE))
+	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))
 		complete(&ua->complete);
 }