soc/amd/stoneyridge: Move I2C bus clear out of gpio.c

Relocate the I2C bus reset code from gpio.c to i2c.c.  When it first
went in, gpio.c was a natural location due to the nature of the
algorithm.  This is preparation for moving most of gpio.c to common
code.

Change-Id: I3b2d8e1b54e7c5929220d763bd99fe01b0636aaa
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32650
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/src/soc/amd/stoneyridge/i2c.c b/src/soc/amd/stoneyridge/i2c.c
index e99f3509ff..c3e5539e19 100644
--- a/src/soc/amd/stoneyridge/i2c.c
+++ b/src/soc/amd/stoneyridge/i2c.c
@@ -13,12 +13,16 @@
  * GNU General Public License for more details.
  */
 
+#include <device/mmio.h>
 #include <arch/acpi.h>
 #include <console/console.h>
+#include <delay.h>
 #include <drivers/i2c/designware/dw_i2c.h>
+#include <amdblocks/acpimmio.h>
 #include <soc/iomap.h>
 #include <soc/pci_devs.h>
 #include <soc/southbridge.h>
+#include <soc/i2c.h>
 #include "chip.h"
 
 #define I2C_BUS_ADDRESS(x) (I2C_BASE_ADDRESS + I2C_DEVICE_SIZE * (x))
@@ -140,3 +144,98 @@ struct device_operations stoneyridge_i2c_mmio_ops = {
 	.acpi_name = i2c_acpi_name,
 	.acpi_fill_ssdt_generator = dw_i2c_acpi_fill_ssdt,
 };
+
+/*
+ * I2C pins are open drain with external pull up, so in order to bit bang them
+ * all, SCL pins must become GPIO inputs with no pull, then they need to be
+ * toggled between input-no-pull and output-low. This table is for the initial
+ * conversion of all SCL pins to input with no pull.
+ */
+static const struct soc_amd_gpio i2c_2_gpi[] = {
+	PAD_GPI(I2C0_SCL_PIN, PULL_NONE),
+	PAD_GPI(I2C1_SCL_PIN, PULL_NONE),
+	PAD_GPI(I2C2_SCL_PIN, PULL_NONE),
+	PAD_GPI(I2C3_SCL_PIN, PULL_NONE),
+};
+#define saved_pins_count ARRAY_SIZE(i2c_2_gpi)
+
+/*
+ * To program I2C pins without destroying their programming, the registers
+ * that will be changed need to be saved first.
+ */
+static void save_i2c_pin_registers(uint8_t gpio,
+					struct soc_amd_i2c_save *save_table)
+{
+	uint32_t *gpio_ptr;
+
+	gpio_ptr = (uint32_t *)gpio_get_address(gpio);
+	save_table->mux_value = iomux_read8(gpio);
+	save_table->control_value = read32(gpio_ptr);
+}
+
+static void restore_i2c_pin_registers(uint8_t gpio,
+					struct soc_amd_i2c_save *save_table)
+{
+	uint32_t *gpio_ptr;
+
+	gpio_ptr = (uint32_t *)gpio_get_address(gpio);
+	iomux_write8(gpio, save_table->mux_value);
+	iomux_read8(gpio);
+	write32(gpio_ptr, save_table->control_value);
+	read32(gpio_ptr);
+}
+
+/* Slaves to be reset are controlled by devicetree register i2c_scl_reset */
+void sb_reset_i2c_slaves(void)
+{
+	const struct soc_amd_stoneyridge_config *cfg;
+	const struct device *dev = pcidev_path_on_root(GNB_DEVFN);
+	struct soc_amd_i2c_save save_table[saved_pins_count];
+	uint8_t i, j, control;
+
+	if (!dev || !dev->chip_info)
+		return;
+	cfg = dev->chip_info;
+	control = cfg->i2c_scl_reset & GPIO_I2C_MASK;
+	if (control == 0)
+		return;
+
+	/* Save and reprogram I2C SCL pins */
+	for (i = 0; i < saved_pins_count; i++)
+		save_i2c_pin_registers(i2c_2_gpi[i].gpio, &save_table[i]);
+	sb_program_gpios(i2c_2_gpi, saved_pins_count);
+
+	/*
+	 * Toggle SCL back and forth 9 times under 100KHz. A single read is
+	 * needed after the writes to force the posted write to complete.
+	 */
+	for (j = 0; j < 9; j++) {
+		if (control & GPIO_I2C0_SCL)
+			write32((uint32_t *)GPIO_I2C0_ADDRESS, GPIO_SCL_LOW);
+		if (control & GPIO_I2C1_SCL)
+			write32((uint32_t *)GPIO_I2C1_ADDRESS, GPIO_SCL_LOW);
+		if (control & GPIO_I2C2_SCL)
+			write32((uint32_t *)GPIO_I2C2_ADDRESS, GPIO_SCL_LOW);
+		if (control & GPIO_I2C3_SCL)
+			write32((uint32_t *)GPIO_I2C3_ADDRESS, GPIO_SCL_LOW);
+
+		read32((uint32_t *)GPIO_I2C3_ADDRESS); /* Flush posted write */
+		udelay(4); /* 4usec gets 85KHz for 1 pin, 70KHz for 4 pins */
+
+		if (control & GPIO_I2C0_SCL)
+			write32((uint32_t *)GPIO_I2C0_ADDRESS, GPIO_SCL_HIGH);
+		if (control & GPIO_I2C1_SCL)
+			write32((uint32_t *)GPIO_I2C1_ADDRESS, GPIO_SCL_HIGH);
+		if (control & GPIO_I2C2_SCL)
+			write32((uint32_t *)GPIO_I2C2_ADDRESS, GPIO_SCL_HIGH);
+		if (control & GPIO_I2C3_SCL)
+			write32((uint32_t *)GPIO_I2C3_ADDRESS, GPIO_SCL_HIGH);
+
+		read32((uint32_t *)GPIO_I2C3_ADDRESS); /* Flush posted write */
+		udelay(4);
+	}
+
+	/* Restore I2C pins. */
+	for (i = 0; i < saved_pins_count; i++)
+		restore_i2c_pin_registers(i2c_2_gpi[i].gpio, &save_table[i]);
+}