arch: cxd56xx: Add logic for i2c reset

Add ARCH_HAVE_I2CRESET configration to ARCH_CHIP_CXD56XX
and implement i2c reset function.

arch/arm/Kconfig

@@ -635,6 +635,7 @@ config ARCH_CHIP_CXD56XX
 	select ARCH_HAVE_TEXT_HEAP
 	select ARCH_HAVE_SDIO if MMCSD
 	select ARCH_HAVE_MATH_H
+	select ARCH_HAVE_I2CRESET
 	---help---
 		Sony CXD56XX (ARM Cortex-M4) architectures
 

arch/arm/src/cxd56xx/cxd56_i2c.c

@@ -46,6 +46,7 @@
 #include "cxd56_i2c.h"
 #include "hardware/cxd56_i2c.h"
 #include "cxd56_pinconfig.h"
+#include "cxd56_gpio.h"
 
 #if defined(CONFIG_CXD56_I2C0_SCUSEQ) || defined(CONFIG_CXD56_I2C1_SCUSEQ)
 #include <arch/chip/scu.h>
@@ -702,7 +703,124 @@ static int cxd56_i2c_transfer(struct i2c_master_s *dev,
 #ifdef CONFIG_I2C_RESET
 static int cxd56_i2c_reset(struct i2c_master_s *dev)
 {
-  return OK;
+  struct cxd56_i2cdev_s *priv = (struct cxd56_i2cdev_s *)dev;
+  unsigned int clock_count;
+  unsigned int stretch_count;
+  uint32_t scl_gpio;
+  uint32_t sda_gpio;
+  int ret = -EIO;
+
+  DEBUGASSERT(dev != NULL);
+
+  /* Our caller must own a ref */
+
+  DEBUGASSERT(priv->refs > 0);
+
+  /* Lock out other clients */
+
+  nxmutex_lock(&priv->lock);
+
+  /* Use GPIO configuration to un-wedge the bus */
+
+  cxd56_i2c_pincontrol(priv->port, false);
+
+  switch (priv->port)
+    {
+      case 0:
+        scl_gpio = PIN_I2C0_BCK;
+        sda_gpio = PIN_I2C0_BDT;
+        break;
+      case 1:
+        scl_gpio = PIN_PWM2;
+        sda_gpio = PIN_PWM3;
+        break;
+      case 2:
+      default:
+        scl_gpio = PIN_SPI0_MOSI;
+        sda_gpio = PIN_SPI0_MISO;
+        break;
+    }
+
+  /* Enable input of SCL and SDA pins */
+
+  cxd56_gpio_config(scl_gpio, true);
+  cxd56_gpio_config(sda_gpio, true);
+
+  /* Let SDA go high */
+
+  cxd56_gpio_write(sda_gpio, true);
+
+  /* Clock the bus until any slaves currently driving it let it go. */
+
+  clock_count = 0;
+  while (!cxd56_gpio_read(sda_gpio))
+    {
+      /* Give up if we have tried too hard */
+
+      if (clock_count++ > 10)
+        {
+          goto out;
+        }
+
+      /* Sniff to make sure that clock stretching has finished.
+       *
+       * If the bus never relaxes, the reset has failed.
+       */
+
+      stretch_count = 0;
+      while (!cxd56_gpio_read(scl_gpio))
+        {
+          /* Give up if we have tried too hard */
+
+          if (stretch_count++ > 10)
+            {
+              goto out;
+            }
+
+          up_udelay(10);
+        }
+
+      /* Drive SCL low */
+
+      cxd56_gpio_write(scl_gpio, false);
+      up_udelay(10);
+
+      /* Drive SCL high again */
+
+      cxd56_gpio_write(scl_gpio, true);
+      up_udelay(10);
+    }
+
+  /* Generate a start followed by a stop to reset slave
+   * state machines.
+   */
+
+  cxd56_gpio_write(sda_gpio, false);
+  up_udelay(10);
+  cxd56_gpio_write(scl_gpio, false);
+  up_udelay(10);
+  cxd56_gpio_write(scl_gpio, true);
+  up_udelay(10);
+  cxd56_gpio_write(sda_gpio, true);
+  up_udelay(10);
+
+  ret = OK;
+
+out:
+
+  /* Disable output of SCL and SDA pins */
+
+  cxd56_gpio_write_hiz(scl_gpio);
+  cxd56_gpio_write_hiz(sda_gpio);
+
+  /* Revert the GPIO configuration. */
+
+  cxd56_i2c_pincontrol(priv->port, true);
+
+  /* Release the port for re-use by other clients */
+
+  nxmutex_unlock(&priv->lock);
+  return ret;
 }
 #endif /* CONFIG_I2C_RESET */