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Date: Thu, 9 May 2024 12:50:36 +0100
From: Diogo Ivo <diogo.ivo@tecnico.ulisboa.pt>
To: heikki.krogerus@linux.intel.com, gregkh@linuxfoundation.org, 
	lk@c--e.de, u.kleine-koenig@pengutronix.de, linux-usb@vger.kernel.org, 
	linux-kernel@vger.kernel.org
Cc: diogo.ivo@tecnico.ulisboa.pt
Subject: [RFC PATCH] usb: typec: ucsi_acpi: Add LG Gram quirk
Message-ID: <5qc55gruhn4pmutiukohauki5dehba6n2k22jgvpt7i3hafkon@v2ng2a33o7vv>
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Some LG Gram laptops report a bogus connector change event after a
GET_PDOS command for the partner's source PDOs, which disappears from
the CCI after acknowledging the command. However, the subsequent
GET_CONNECTOR_STATUS in ucsi_handle_connector_change() still reports
this bogus change in bits 5 and 6, leading to the UCSI core re-checking
the partner's source PDOs and thus to an infinite loop.

Fix this by adding a quirk that signals when a potentially buggy GET_PDOS
command is used, checks the status change report and clears it if it is a
bogus event before sending it to the UCSI core.

[Sending as RFC both to see if this is a good idea and so that more
users can test it to gather all the models affected by this bug.]

Signed-off-by: Diogo Ivo <diogo.ivo@tecnico.ulisboa.pt>
---
 drivers/usb/typec/ucsi/ucsi_acpi.c | 60 ++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/drivers/usb/typec/ucsi/ucsi_acpi.c b/drivers/usb/typec/ucsi/ucsi_acpi.c
index 8d112c3edae5..c67607f68b44 100644
--- a/drivers/usb/typec/ucsi/ucsi_acpi.c
+++ b/drivers/usb/typec/ucsi/ucsi_acpi.c
@@ -25,6 +25,7 @@ struct ucsi_acpi {
 	unsigned long flags;
 #define UCSI_ACPI_COMMAND_PENDING	1
 #define UCSI_ACPI_ACK_PENDING		2
+#define UCSI_ACPI_CHECK_BOGUS_EVENT	4
 	guid_t guid;
 	u64 cmd;
 };
@@ -128,6 +129,58 @@ static const struct ucsi_operations ucsi_zenbook_ops = {
 	.async_write = ucsi_acpi_async_write
 };
 
+static int ucsi_gram_read(struct ucsi *ucsi, unsigned int offset,
+			  void *val, size_t val_len)
+{
+	u16 bogus_change = UCSI_CONSTAT_POWER_LEVEL_CHANGE |
+			   UCSI_CONSTAT_PDOS_CHANGE;
+	struct ucsi_acpi *ua = ucsi_get_drvdata(ucsi);
+	struct ucsi_connector_status *status;
+	int ret;
+
+	ret = ucsi_acpi_read(ucsi, offset, val, val_len);
+	if (ret < 0)
+		return ret;
+
+	if (UCSI_COMMAND(ua->cmd) == UCSI_GET_CONNECTOR_STATUS &&
+	    ua->flags & UCSI_ACPI_CHECK_BOGUS_EVENT &&
+	    offset == UCSI_MESSAGE_IN) {
+		status = (struct ucsi_connector_status *)val;
+
+		/* Clear the bogus change */
+		if (status->change == bogus_change)
+			status->change = 0;
+
+		ua->flags &= ~UCSI_ACPI_CHECK_BOGUS_EVENT;
+	}
+
+	return ret;
+}
+
+static int ucsi_gram_sync_write(struct ucsi *ucsi, unsigned int offset,
+				const void *val, size_t val_len)
+{
+	struct ucsi_acpi *ua = ucsi_get_drvdata(ucsi);
+	int ret;
+
+	ret = ucsi_acpi_sync_write(ucsi, offset, val, val_len);
+	if (ret < 0)
+		return ret;
+
+	if (UCSI_COMMAND(ua->cmd) == UCSI_GET_PDOS &&
+	    ua->cmd & UCSI_GET_PDOS_PARTNER_PDO(1) &&
+	    ua->cmd & UCSI_GET_PDOS_SRC_PDOS)
+		ua->flags |= UCSI_ACPI_CHECK_BOGUS_EVENT;
+
+	return ret;
+}
+
+static const struct ucsi_operations ucsi_gram_ops = {
+	.read = ucsi_gram_read,
+	.sync_write = ucsi_gram_sync_write,
+	.async_write = ucsi_acpi_async_write
+};
+
 static const struct dmi_system_id ucsi_acpi_quirks[] = {
 	{
 		.matches = {
@@ -136,6 +189,13 @@ static const struct dmi_system_id ucsi_acpi_quirks[] = {
 		},
 		.driver_data = (void *)&ucsi_zenbook_ops,
 	},
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LG Electronics"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Z90Q"),
+		},
+		.driver_data = (void *)&ucsi_gram_ops,
+	},
 	{ }
 };
 
-- 
2.45.0