[PATCH v4 1/4] i2c: at91: Send bus clear command if SDA is down
From: Codrin Ciubotariu
Date: Tue Feb 25 2020 - 10:50:25 EST
After a transfer timeout, some faulty I2C slave devices might hold down
the SDA pin. We can generate a bus clear command, hoping that the slave
might release the pins.
If the CLEAR command is not supported, we will use gpio recovery, if
available, to reset the bus.
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
---
Changes in v4:
- moved the HW bus clear command in a recover_bus() function, to be able
to just call i2c_recover_bus() if a transfer fails;
- recovery gpios are no longer taken if HW bus clear command is
supported;
Changes in v3:
- removed unnecessary condition from info print;
- removed unneded declarations;
Changes in v2:
- called i2c_recover_bus() after an error occurs, if SDA is down;
- release gpios if recovery information is incomplete;
drivers/i2c/busses/i2c-at91-core.c | 2 ++
drivers/i2c/busses/i2c-at91-master.c | 49 ++++++++++++++++++++++++----
drivers/i2c/busses/i2c-at91.h | 7 +++-
3 files changed, 50 insertions(+), 8 deletions(-)
diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
index 3da1a8acecb5..e14edd236108 100644
--- a/drivers/i2c/busses/i2c-at91-core.c
+++ b/drivers/i2c/busses/i2c-at91-core.c
@@ -131,6 +131,7 @@ static struct at91_twi_pdata sama5d2_config = {
.has_dig_filtr = true,
.has_adv_dig_filtr = true,
.has_ana_filtr = true,
+ .has_clear_cmd = false, /* due to errata, CLEAR cmd is not working */
};
static struct at91_twi_pdata sam9x60_config = {
@@ -142,6 +143,7 @@ static struct at91_twi_pdata sam9x60_config = {
.has_dig_filtr = true,
.has_adv_dig_filtr = true,
.has_ana_filtr = true,
+ .has_clear_cmd = true,
};
static const struct of_device_id atmel_twi_dt_ids[] = {
diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
index 0aba51a7df32..776e95962ab6 100644
--- a/drivers/i2c/busses/i2c-at91-master.c
+++ b/drivers/i2c/busses/i2c-at91-master.c
@@ -480,7 +480,6 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
unsigned long time_left;
bool has_unre_flag = dev->pdata->has_unre_flag;
bool has_alt_cmd = dev->pdata->has_alt_cmd;
- struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
/*
* WARNING: the TXCOMP bit in the Status Register is NOT a clear on
@@ -641,11 +640,12 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
}
- if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
- dev_dbg(dev->dev,
- "SDA is down; clear bus using gpio\n");
- i2c_recover_bus(&dev->adapter);
- }
+ /*
+ * some faulty I2C slave devices might hold SDA down;
+ * we can send a bus clear command, hoping that the pins will be
+ * released
+ */
+ i2c_recover_bus(&dev->adapter);
return ret;
}
@@ -830,7 +830,7 @@ static void at91_unprepare_twi_recovery(struct i2c_adapter *adap)
pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
}
-static int at91_init_twi_recovery_info(struct platform_device *pdev,
+static int at91_init_twi_recovery_gpio(struct platform_device *pdev,
struct at91_twi_dev *dev)
{
struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
@@ -880,6 +880,41 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev,
return 0;
}
+static int at91_twi_recover_bus_cmd(struct i2c_adapter *adap)
+{
+ struct at91_twi_dev *dev = i2c_get_adapdata(adap);
+
+ dev->transfer_status |= at91_twi_read(dev, AT91_TWI_SR);
+ if (!(dev->transfer_status & AT91_TWI_SDA)) {
+ dev_dbg(dev->dev, "SDA is down; sending bus clear command\n");
+ if (dev->use_alt_cmd) {
+ unsigned int acr;
+
+ acr = at91_twi_read(dev, AT91_TWI_ACR);
+ acr &= ~AT91_TWI_ACR_DATAL_MASK;
+ at91_twi_write(dev, AT91_TWI_ACR, acr);
+ }
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);
+ }
+
+ return 0;
+}
+
+static int at91_init_twi_recovery_info(struct platform_device *pdev,
+ struct at91_twi_dev *dev)
+{
+ struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
+ bool has_clear_cmd = dev->pdata->has_clear_cmd;
+
+ if (!has_clear_cmd)
+ return at91_init_twi_recovery_gpio(pdev, dev);
+
+ rinfo->recover_bus = at91_twi_recover_bus_cmd;
+ dev->adapter.bus_recovery_info = rinfo;
+
+ return 0;
+}
+
int at91_twi_probe_master(struct platform_device *pdev,
u32 phy_addr, struct at91_twi_dev *dev)
{
diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
index f57a6cab96b4..7e7b4955ca7f 100644
--- a/drivers/i2c/busses/i2c-at91.h
+++ b/drivers/i2c/busses/i2c-at91.h
@@ -36,6 +36,7 @@
#define AT91_TWI_SVDIS BIT(5) /* Slave Transfer Disable */
#define AT91_TWI_QUICK BIT(6) /* SMBus quick command */
#define AT91_TWI_SWRST BIT(7) /* Software Reset */
+#define AT91_TWI_CLEAR BIT(15) /* Bus clear command */
#define AT91_TWI_ACMEN BIT(16) /* Alternative Command Mode Enable */
#define AT91_TWI_ACMDIS BIT(17) /* Alternative Command Mode Disable */
#define AT91_TWI_THRCLR BIT(24) /* Transmit Holding Register Clear */
@@ -69,6 +70,8 @@
#define AT91_TWI_NACK BIT(8) /* Not Acknowledged */
#define AT91_TWI_EOSACC BIT(11) /* End Of Slave Access */
#define AT91_TWI_LOCK BIT(23) /* TWI Lock due to Frame Errors */
+#define AT91_TWI_SCL BIT(24) /* TWI SCL status */
+#define AT91_TWI_SDA BIT(25) /* TWI SDA status */
#define AT91_TWI_INT_MASK \
(AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
@@ -81,7 +84,8 @@
#define AT91_TWI_THR 0x0034 /* Transmit Holding Register */
#define AT91_TWI_ACR 0x0040 /* Alternative Command Register */
-#define AT91_TWI_ACR_DATAL(len) ((len) & 0xff)
+#define AT91_TWI_ACR_DATAL_MASK GENMASK(15, 0)
+#define AT91_TWI_ACR_DATAL(len) ((len) & AT91_TWI_ACR_DATAL_MASK)
#define AT91_TWI_ACR_DIR BIT(8)
#define AT91_TWI_FILTR 0x0044
@@ -118,6 +122,7 @@ struct at91_twi_pdata {
bool has_dig_filtr;
bool has_adv_dig_filtr;
bool has_ana_filtr;
+ bool has_clear_cmd;
struct at_dma_slave dma_slave;
};
--
2.20.1