HID: mcp2221: set gpio pin mode

in case we have GPIOLIB enabled the gpio pins are used
from the current driver as gpio pins. But may the gpio
functions of this pins are not enabled in the flash
of the chip and so gpio access fails.

In case CONFIG_IIO is not enabled we can prevent this
issue of the driver simply by enabling the gpio mode
for all pins.

Signed-off-by: Heiko Schocher <[email protected]>
Signed-off-by: Jiri Kosina <[email protected]>

Author: hsdenx

drivers/hid/hid-mcp2221.c

@@ -55,6 +55,27 @@ enum {
 	MCP2221_ALT_F_NOT_GPIOD = 0xEF,
 };
 
+/* MCP SRAM read offsets cmd: MCP2221_GET_SRAM_SETTINGS */
+enum {
+	MCP2221_SRAM_RD_GP0 = 22,
+	MCP2221_SRAM_RD_GP1 = 23,
+	MCP2221_SRAM_RD_GP2 = 24,
+	MCP2221_SRAM_RD_GP3 = 25,
+};
+
+/* MCP SRAM write offsets cmd: MCP2221_SET_SRAM_SETTINGS */
+enum {
+	MCP2221_SRAM_WR_GP_ENA_ALTER = 7,
+	MCP2221_SRAM_WR_GP0 = 8,
+	MCP2221_SRAM_WR_GP1 = 9,
+	MCP2221_SRAM_WR_GP2 = 10,
+	MCP2221_SRAM_WR_GP3 = 11,
+};
+
+#define MCP2221_SRAM_GP_DESIGN_MASK		0x07
+#define MCP2221_SRAM_GP_DIRECTION_MASK		0x08
+#define MCP2221_SRAM_GP_VALUE_MASK		0x10
+
 /* MCP GPIO direction encoding */
 enum {
 	MCP2221_DIR_OUT = 0x00,
@@ -607,6 +628,80 @@ static const struct i2c_algorithm mcp_i2c_algo = {
 };
 
 #if IS_REACHABLE(CONFIG_GPIOLIB)
+static int mcp_gpio_read_sram(struct mcp2221 *mcp)
+{
+	int ret;
+
+	memset(mcp->txbuf, 0, 64);
+	mcp->txbuf[0] = MCP2221_GET_SRAM_SETTINGS;
+
+	mutex_lock(&mcp->lock);
+	ret = mcp_send_data_req_status(mcp, mcp->txbuf, 64);
+	mutex_unlock(&mcp->lock);
+
+	return ret;
+}
+
+/*
+ * If CONFIG_IIO is not enabled, check for the gpio pins
+ * if they are in gpio mode. For the ones which are not
+ * in gpio mode, set them into gpio mode.
+ */
+static int mcp2221_check_gpio_pinfunc(struct mcp2221 *mcp)
+{
+	int i;
+	int needgpiofix = 0;
+	int ret;
+
+	if (IS_ENABLED(CONFIG_IIO))
+		return 0;
+
+	ret = mcp_gpio_read_sram(mcp);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < MCP_NGPIO; i++) {
+		if ((mcp->mode[i] & MCP2221_SRAM_GP_DESIGN_MASK) != 0x0) {
+			dev_warn(&mcp->hdev->dev,
+				 "GPIO %d not in gpio mode\n", i);
+			needgpiofix = 1;
+		}
+	}
+
+	if (!needgpiofix)
+		return 0;
+
+	/*
+	 * Set all bytes to 0, so Bit 7 is not set. The chip
+	 * only changes content of a register when bit 7 is set.
+	 */
+	memset(mcp->txbuf, 0, 64);
+	mcp->txbuf[0] = MCP2221_SET_SRAM_SETTINGS;
+
+	/*
+	 * Set bit 7 in MCP2221_SRAM_WR_GP_ENA_ALTER to enable
+	 * loading of a new set of gpio settings to GP SRAM
+	 */
+	mcp->txbuf[MCP2221_SRAM_WR_GP_ENA_ALTER] = 0x80;
+	for (i = 0; i < MCP_NGPIO; i++) {
+		if ((mcp->mode[i] & MCP2221_SRAM_GP_DESIGN_MASK) == 0x0) {
+			/* write current GPIO mode */
+			mcp->txbuf[MCP2221_SRAM_WR_GP0 + i] = mcp->mode[i];
+		} else {
+			/* pin is not in gpio mode, set it to input mode */
+			mcp->txbuf[MCP2221_SRAM_WR_GP0 + i] = 0x08;
+			dev_warn(&mcp->hdev->dev,
+				 "Set GPIO mode for gpio pin %d!\n", i);
+		}
+	}
+
+	mutex_lock(&mcp->lock);
+	ret = mcp_send_data_req_status(mcp, mcp->txbuf, 64);
+	mutex_unlock(&mcp->lock);
+
+	return ret;
+}
+
 static int mcp_gpio_get(struct gpio_chip *gc,
 				unsigned int offset)
 {
@@ -1218,6 +1313,8 @@ static int mcp2221_probe(struct hid_device *hdev,
 	ret = devm_gpiochip_add_data(&hdev->dev, mcp->gc, mcp);
 	if (ret)
 		return ret;
+
+	mcp2221_check_gpio_pinfunc(mcp);
 #endif
 
 #if IS_REACHABLE(CONFIG_IIO)