i2c: at91: Send bus clear command if SDA is down

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@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
index 3da1a8a..e14edd2 100644 (file)
--- 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 0aba51a..776e959 100644 (file)
--- 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 @@ error:
                               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 f57a6ca..7e7b495 100644 (file)
--- 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;
 };