linux-kernel - [PATCH] USB: serial: cp210x: Fix alternate function for CP2102N QFN20

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Message-Id: <51830b2b24118eb0f77c5c9ac64ffb2f519dbb1d.1622218300.git.stefan@agner.ch>
Date:   Fri, 28 May 2021 22:39:31 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     johan@...nel.org
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefan@...er.ch
Subject: [PATCH] USB: serial: cp210x: Fix alternate function for CP2102N QFN20

The QFN20 part has a different GPIO/port function assignment. The
configuration struct bit field ordered as TX/RX/RS485/WAKEUP/CLK
which exactly matches GPIO0-3 for QFN24/28. However, QFN20 has a
different GPIO to primary function assignment.

Special case QFN20 to follow to properly detect which GPIOs are
available.

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
Tested on a custom PCB with a CP2102N QFP20 device. I noticed the bug after
configuring GPIO.2/3 to be TX/RX LED.

--
Stefan

 drivers/usb/serial/cp210x.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index ee595d1bea0a..c9f8ebd34122 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -537,6 +537,12 @@ struct cp210x_single_port_config {
 #define CP210X_2NCONFIG_GPIO_RSTLATCH_IDX	587
 #define CP210X_2NCONFIG_GPIO_CONTROL_IDX	600
 
+/* CP2102N QFN20 port configuration values */
+#define CP2102N_QFN20_GPIO2_TXLED_MODE		BIT(2)
+#define CP2102N_QFN20_GPIO3_RXLED_MODE		BIT(3)
+#define CP2102N_QFN20_GPIO1_RS485_MODE		BIT(4)
+#define CP2102N_QFN20_GPIO0_CLK_MODE		BIT(6)
+
 /* CP210X_VENDOR_SPECIFIC, CP210X_WRITE_LATCH call writes these 0x2 bytes. */
 struct cp210x_gpio_write {
 	u8	mask;
@@ -1733,7 +1739,19 @@ static int cp2102n_gpioconf_init(struct usb_serial *serial)
 	priv->gpio_pushpull = (gpio_pushpull >> 3) & 0x0f;
 
 	/* 0 indicates GPIO mode, 1 is alternate function */
-	priv->gpio_altfunc = (gpio_ctrl >> 2) & 0x0f;
+	if (priv->partnum == CP210X_PARTNUM_CP2102N_QFN20) {
+		/* QFN20 is special... */
+		if (gpio_ctrl & CP2102N_QFN20_GPIO0_CLK_MODE)   /* GPIO 0 */
+			priv->gpio_altfunc |= BIT(0);
+		if (gpio_ctrl & CP2102N_QFN20_GPIO1_RS485_MODE) /* GPIO 1 */
+			priv->gpio_altfunc |= BIT(1);
+		if (gpio_ctrl & CP2102N_QFN20_GPIO2_TXLED_MODE) /* GPIO 2 */
+			priv->gpio_altfunc |= BIT(2);
+		if (gpio_ctrl & CP2102N_QFN20_GPIO3_RXLED_MODE) /* GPIO 3 */
+			priv->gpio_altfunc |= BIT(3);
+	} else {
+		priv->gpio_altfunc = (gpio_ctrl >> 2) & 0x0f;
+	}
 
 	if (priv->partnum == CP210X_PARTNUM_CP2102N_QFN28) {
 		/*
-- 
2.31.1