[PATCH 2/4] i2c: core: add generic I2C GPIO recovery
Codrin Ciubotariu
codrin.ciubotariu at microchip.com
Tue Aug 4 05:59:24 EDT 2020
Multiple I2C bus drivers use similar bindings to obtain information needed
for I2C recovery. For example, for platforms using device-tree, the
properties look something like this:
&i2c {
...
pinctrl-names = "default", "gpio";
pinctrl-0 = <&pinctrl_i2c_default>;
pinctrl-1 = <&pinctrl_i2c_gpio>;
sda-gpios = <&pio 0 GPIO_ACTIVE_HIGH>;
scl-gpios = <&pio 1 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
...
}
For this reason, we can add this common initialization in the core. This
way, other I2C bus drivers will be able to support GPIO recovery just by
providing a pointer to platform's pinctrl and calling i2c_recover_bus()
when SDA is stuck low.
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu at microchip.com>
---
Changes from RFC:
- removed comment with "recovery" pinctrl state from description;
- pinctrl state is changed to gpio after calling prepare_recovery()
callback;
- addressed requested changes on comments;
- removed cleanup_pinctrl label from i2c_gpio_init_pinctrl_recovery()
- added glitch protection for SDA line when its corresponding gpio is
taken at initialization;
drivers/i2c/i2c-core-base.c | 126 ++++++++++++++++++++++++++++++++++++
include/linux/i2c.h | 11 ++++
2 files changed, 137 insertions(+)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 69217d2193da..cf0c5eb152e1 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -32,6 +32,7 @@
#include <linux/of_device.h>
#include <linux/of.h>
#include <linux/of_irq.h>
+#include <linux/pinctrl/consumer.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/pm_wakeirq.h>
@@ -181,6 +182,8 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap)
if (bri->prepare_recovery)
bri->prepare_recovery(adap);
+ if (bri->pinctrl)
+ pinctrl_select_state(bri->pinctrl, bri->pins_gpio);
/*
* If we can set SDA, we will always create a STOP to ensure additional
@@ -236,6 +239,8 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap)
if (bri->unprepare_recovery)
bri->unprepare_recovery(adap);
+ if (bri->pinctrl)
+ pinctrl_select_state(bri->pinctrl, bri->pins_default);
return ret;
}
@@ -251,6 +256,125 @@ int i2c_recover_bus(struct i2c_adapter *adap)
}
EXPORT_SYMBOL_GPL(i2c_recover_bus);
+static void i2c_gpio_init_pinctrl_recovery(struct i2c_adapter *adap)
+{
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+ struct device *dev = &adap->dev;
+ struct pinctrl *p = bri->pinctrl;
+
+ /*
+ * we can't change states without pinctrl, so remove the states if
+ * populated
+ */
+ if (!p) {
+ bri->pins_default = NULL;
+ bri->pins_gpio = NULL;
+ return;
+ }
+
+ if (!bri->pins_default) {
+ bri->pins_default = pinctrl_lookup_state(p,
+ PINCTRL_STATE_DEFAULT);
+ if (IS_ERR(bri->pins_default)) {
+ dev_dbg(dev, PINCTRL_STATE_DEFAULT " state not found for GPIO recovery\n");
+ bri->pins_default = NULL;
+ }
+ }
+ if (!bri->pins_gpio) {
+ bri->pins_gpio = pinctrl_lookup_state(p, "gpio");
+ if (IS_ERR(bri->pins_gpio))
+ bri->pins_gpio = pinctrl_lookup_state(p, "recovery");
+
+ if (IS_ERR(bri->pins_gpio)) {
+ dev_dbg(dev, "no gpio or recovery state found for GPIO recovery\n");
+ bri->pins_gpio = NULL;
+ }
+ }
+
+ /* for pinctrl state changes, we need all the information */
+ if (!bri->pins_default || !bri->pins_gpio) {
+ bri->pinctrl = NULL;
+ bri->pins_default = NULL;
+ bri->pins_gpio = NULL;
+ } else {
+ dev_info(dev, "using pinctrl states for GPIO recovery");
+ }
+}
+
+static int i2c_gpio_init_generic_recovery(struct i2c_adapter *adap)
+{
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+ struct device *dev = &adap->dev;
+ struct gpio_desc *gpiod;
+ int ret = 0;
+
+ /*
+ * don't touch the recovery information if the driver is not using
+ * generic SCL recovery
+ */
+ if (bri->recover_bus && bri->recover_bus != i2c_generic_scl_recovery)
+ return 0;
+
+ /*
+ * pins might be taken as GPIO, so we should inform pinctrl about
+ * this and move the state to GPIO
+ */
+ if (bri->pinctrl)
+ pinctrl_select_state(bri->pinctrl, bri->pins_gpio);
+
+ /*
+ * if there is incomplete or no recovery information, see if generic
+ * GPIO recovery is available
+ */
+ if (!bri->scl_gpiod) {
+ gpiod = devm_gpiod_get(dev, "scl", GPIOD_OUT_HIGH_OPEN_DRAIN);
+ if (PTR_ERR(gpiod) == -EPROBE_DEFER) {
+ ret = -EPROBE_DEFER;
+ goto cleanup_pinctrl_state;
+ }
+ if (!IS_ERR(gpiod)) {
+ bri->scl_gpiod = gpiod;
+ bri->recover_bus = i2c_generic_scl_recovery;
+ dev_info(dev, "using generic GPIOs for recovery\n");
+ }
+ }
+
+ /* SDA GPIOD line is optional, so we care about DEFER only */
+ if (!bri->sda_gpiod) {
+ /*
+ * We have SCL. Pull SCL low and wait a bit so that SDA glitches
+ * have no effect.
+ */
+ gpiod_direction_output(bri->scl_gpiod, 0);
+ udelay(10);
+ gpiod = devm_gpiod_get(dev, "sda", GPIOD_IN);
+
+ /* Wait a bit in case of a SDA glitch, and then release SCL. */
+ udelay(10);
+ gpiod_direction_output(bri->scl_gpiod, 1);
+
+ if (PTR_ERR(gpiod) == -EPROBE_DEFER) {
+ ret = -EPROBE_DEFER;
+ goto cleanup_pinctrl_state;
+ }
+ if (!IS_ERR(gpiod))
+ bri->sda_gpiod = gpiod;
+ }
+
+cleanup_pinctrl_state:
+ /* change the state of the pins back to their default state */
+ if (bri->pinctrl)
+ pinctrl_select_state(bri->pinctrl, bri->pins_default);
+
+ return ret;
+}
+
+static int i2c_gpio_init_recovery(struct i2c_adapter *adap)
+{
+ i2c_gpio_init_pinctrl_recovery(adap);
+ return i2c_gpio_init_generic_recovery(adap);
+}
+
static void i2c_init_recovery(struct i2c_adapter *adap)
{
struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
@@ -259,6 +383,8 @@ static void i2c_init_recovery(struct i2c_adapter *adap)
if (!bri)
return;
+ i2c_gpio_init_recovery(adap);
+
if (!bri->recover_bus) {
err_str = "no recover_bus() found";
goto err;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 176bf971cbe0..93b6b698f150 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -606,6 +606,14 @@ struct i2c_timings {
* may configure padmux here for SDA/SCL line or something else they want.
* @scl_gpiod: gpiod of the SCL line. Only required for GPIO recovery.
* @sda_gpiod: gpiod of the SDA line. Only required for GPIO recovery.
+ * @pinctrl: pinctrl used by GPIO recovery to change the state of the I2C pins.
+ * Optional.
+ * @pins_default: default state of SCL/SDA lines, when they are assigned to the
+ * I2C bus. Optional. Populated internally for GPIO recovery, if a state with
+ * the name PINCTRL_STATE_DEFAULT is found and pinctrl is valid.
+ * @pins_gpio: recovery state of SCL/SDA lines, when they are used as GPIOs.
+ * Optional. Populated internally for GPIO recovery, if this state is called
+ * "gpio" or "recovery" and pinctrl is valid.
*/
struct i2c_bus_recovery_info {
int (*recover_bus)(struct i2c_adapter *adap);
@@ -622,6 +630,9 @@ struct i2c_bus_recovery_info {
/* gpio recovery */
struct gpio_desc *scl_gpiod;
struct gpio_desc *sda_gpiod;
+ struct pinctrl *pinctrl;
+ struct pinctrl_state *pins_default;
+ struct pinctrl_state *pins_gpio;
};
int i2c_recover_bus(struct i2c_adapter *adap);
--
2.25.1
More information about the linux-arm-kernel
mailing list