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

Christian A. Ehrhardt
2024-03-20T07:40:16Z

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>
---
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