linux-kernel - [PATCH v2 3/3] platform/chrome: cros_ec_spi: Boot fingerprint processor during probe

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Message-Id: <20220317005814.2496302-4-swboyd@chromium.org>
Date:   Wed, 16 Mar 2022 17:58:14 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Benson Leung <bleung@...omium.org>
Cc:     linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev,
        Guenter Roeck <groeck@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Craig Hesling <hesling@...omium.org>,
        Tom Hughes <tomhughes@...omium.org>,
        Alexandru M Stan <amstan@...omium.org>,
        Tzung-Bi Shih <tzungbi@...nel.org>
Subject: [PATCH v2 3/3] platform/chrome: cros_ec_spi: Boot fingerprint processor during probe

Add gpio control to this driver so that the fingerprint device can be
booted if the BIOS isn't doing it already. This eases bringup of new
hardware as we don't have to wait for the BIOS to be ready, supports
kexec where the GPIOs may not be configured by the previous boot stage,
and is all around good hygiene because we control GPIOs for this device
from the device driver.

Cc: Guenter Roeck <groeck@...omium.org>
Cc: Douglas Anderson <dianders@...omium.org>
Cc: Craig Hesling <hesling@...omium.org>
Cc: Tom Hughes <tomhughes@...omium.org>
Cc: Alexandru M Stan <amstan@...omium.org>
Cc: Tzung-Bi Shih <tzungbi@...nel.org>
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
---
 drivers/platform/chrome/cros_ec_spi.c | 42 +++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_spi.c b/drivers/platform/chrome/cros_ec_spi.c
index d0f9496076d6..13d413a2fe46 100644
--- a/drivers/platform/chrome/cros_ec_spi.c
+++ b/drivers/platform/chrome/cros_ec_spi.c
@@ -4,6 +4,7 @@
 // Copyright (C) 2012 Google, Inc
 
 #include <linux/delay.h>
+#include <linux/gpio/consumer.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -77,6 +78,8 @@ struct cros_ec_spi {
 	unsigned int start_of_msg_delay;
 	unsigned int end_of_msg_delay;
 	struct kthread_worker *high_pri_worker;
+	struct gpio_desc *boot0;
+	struct gpio_desc *reset;
 };
 
 typedef int (*cros_ec_xfer_fn_t) (struct cros_ec_device *ec_dev,
@@ -690,7 +693,7 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
 	return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_cmd_xfer_spi);
 }
 
-static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
+static int cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
 {
 	struct device_node *np = dev->of_node;
 	u32 val;
@@ -703,6 +706,37 @@ static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
 	ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
 	if (!ret)
 		ec_spi->end_of_msg_delay = val;
+
+	if (!of_device_is_compatible(np, "google,cros-ec-fp"))
+		return 0;
+
+	ec_spi->boot0 = devm_gpiod_get(dev, "boot0", 0);
+	if (IS_ERR(ec_spi->boot0))
+		return PTR_ERR(ec_spi->boot0);
+
+	ec_spi->reset = devm_gpiod_get(dev, "reset", 0);
+	if (IS_ERR(ec_spi->reset))
+		return PTR_ERR(ec_spi->reset);
+
+	/*
+	 * Take the FPMCU out of reset and wait for it to boot if it's in
+	 * bootloader mode or held in reset. This isn't the normal flow because
+	 * typically the BIOS has already powered on the device to avoid the
+	 * multi-second delay waiting for the FPMCU to boot and be responsive.
+	 */
+	if (gpiod_get_value(ec_spi->boot0) || gpiod_get_value(ec_spi->reset)) {
+		/* Boot0 is sampled on reset deassertion */
+		gpiod_set_value(ec_spi->boot0, 0);
+		gpiod_set_value(ec_spi->reset, 1);
+		usleep_range(1000, 2000);
+		gpiod_set_value(ec_spi->reset, 0);
+
+		/* Wait for boot; there isn't a "boot done" signal */
+		dev_info(dev, "Waiting for FPMCU to boot\n");
+		msleep(2000);
+	}
+
+	return 0;
 }
 
 static void cros_ec_spi_high_pri_release(void *worker)
@@ -754,8 +788,10 @@ static int cros_ec_spi_probe(struct spi_device *spi)
 	if (!ec_dev)
 		return -ENOMEM;
 
-	/* Check for any DT properties */
-	cros_ec_spi_dt_probe(ec_spi, dev);
+	/* Check for any DT properties and boot FPMCU if applicable */
+	err = cros_ec_spi_dt_probe(ec_spi, dev);
+	if (err)
+		return err;
 
 	spi_set_drvdata(spi, ec_dev);
 	ec_dev->dev = dev;
-- 
https://chromeos.dev