skylake: gpio: Add support for setting 1.8V tolerant

Add the voltage tolerance GPIO attribute for configuring I2C/I2S buses
that are at 1.8V.  This is currently done by passing in a value to FSP
but it is needed earlier than FSP if the I2C bus is used in verstage.

This does not remove the need for the FSP input parameter, that is
still required so FSP doesn't disable what has been set in coreboot.
The mainboards that are affected are updated in this commit.

This was tested by exercising I2C transactions to the 1.8V codec while
in verstage on the google/chell mainboard.

Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Change-Id: I93d22c2e3bc0617c87f03c37a8746e22a112cc9c
Reviewed-on: https://review.coreboot.org/15103
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

3 files changed, 27 insertions, 11 deletions

diff --git a/src/soc/intel/skylake/gpio.c b/src/soc/intel/skylake/gpio.c
index a7d88326d1..78495c6467 100644
--- a/src/soc/intel/skylake/gpio.c
+++ b/src/soc/intel/skylake/gpio.c
@@ -305,9 +305,8 @@ static void gpio_configure_pad(const struct pad_config *cfg)
 {
 	uint32_t *dw_regs;
 	uint32_t reg;
-	uint32_t termination;
 	uint32_t dw0;
-	const uint32_t termination_mask = PAD_TERM_MASK << PAD_TERM_SHIFT;
+	uint32_t mask;
 
 	dw_regs = gpio_dw_regs(cfg->pad);
 
@@ -318,10 +317,16 @@ static void gpio_configure_pad(const struct pad_config *cfg)
 
 	write32(&dw_regs[0], dw0);
 	reg = read32(&dw_regs[1]);
-	reg &= ~termination_mask;
-	termination = cfg->attrs;
-	termination &= termination_mask;
-	reg |= termination;
+
+	/* Apply termination field */
+	mask = PAD_TERM_MASK << PAD_TERM_SHIFT;
+	reg &= ~mask;
+	reg |= cfg->attrs & mask;
+
+	/* Apply voltage tolerance field */
+	mask = PAD_TOL_MASK << PAD_TOL_SHIFT;
+	reg &= ~mask;
+	reg |= cfg->attrs & mask;
 	write32(&dw_regs[1], reg);
 
 	gpio_handle_pad_mode(cfg);
@@ -329,7 +334,7 @@ static void gpio_configure_pad(const struct pad_config *cfg)
 	if ((dw0 & PAD_FIELD(GPIROUTSMI, MASK)) == PAD_FIELD(GPIROUTSMI, YES))
 		gpi_enable_smi(cfg->pad);
 
-	if(gpio_debug)
+	if (gpio_debug)
 		printk(BIOS_DEBUG,
 			"Write Pad: Base(%p) - conf0 = %x conf1= %x pad # = %d\n",
 			&dw_regs[0], dw0, reg, cfg->pad);
diff --git a/src/soc/intel/skylake/include/soc/gpio.h b/src/soc/intel/skylake/include/soc/gpio.h
index f2246e9116..6733889d1a 100644
--- a/src/soc/intel/skylake/include/soc/gpio.h
+++ b/src/soc/intel/skylake/include/soc/gpio.h
@@ -108,6 +108,12 @@ void gpio_configure_pads(const struct pad_config *cfgs, size_t num);
 	_PAD_CFG(pad_, term_, \
 	_DW0_VALS(rst_, RAW, NO, LEVEL, NO, NO, NO, NO, NO, NO, func_, NO, NO))
 
+/* Native 1.8V tolerant pad, only applies to some pads like I2C/I2S. */
+#define PAD_CFG_NF_1V8(pad_, term_, rst_, func_) \
+	_PAD_CFG_ATTRS(pad_, term_, \
+	_DW0_VALS(rst_, RAW, NO, LEVEL, NO, NO, \
+		NO, NO, NO, NO, func_, NO, NO), PAD_FIELD(PAD_TOL, 1V8))
+
 /* Unused PINS will be controlled by GPIO controller (PMODE = GPIO) and
    GPIO TX/RX will be disabled. */
 #define PAD_CFG_NC(pad_) \
@@ -149,9 +155,9 @@ void gpio_configure_pads(const struct pad_config *cfgs, size_t num);
 		NO, NO, YES, NO, GPIO, NO, YES), PAD_FIELD(HOSTSW, ACPI))
 
 /*
- * The 'attrs' field carries the termination in bits 13:10 to match up with
- * thd DW1 pad configuration register. Additionally, other attributes can
- * be applied such as the ones below. Bit allocation matters.
+ * The 'attrs' field carries the termination in bits 13:10 and tolerance in bit
+ * 25 to match up with thd DW1 pad configuration register. Additionally, other
+ * attributes can be applied such as the ones below. Bit allocation matters.
  */
 #define HOSTSW_SHIFT		0
 #define HOSTSW_MASK		1
@@ -160,7 +166,7 @@ void gpio_configure_pads(const struct pad_config *cfgs, size_t num);
 
 struct pad_config {
 	uint16_t pad;
-	uint16_t attrs;
+	uint32_t attrs;
 	uint32_t dw0;
 };
 
diff --git a/src/soc/intel/skylake/include/soc/gpio_defs.h b/src/soc/intel/skylake/include/soc/gpio_defs.h
index 6f9c11134b..4008dfe31d 100644
--- a/src/soc/intel/skylake/include/soc/gpio_defs.h
+++ b/src/soc/intel/skylake/include/soc/gpio_defs.h
@@ -495,6 +495,11 @@
 #define  PAD_TERM_20K_PU	12
 #define  PAD_TERM_667_PU	13
 #define  PAD_TERM_NATIVE	15
+	/* TOL - voltage tolerance */
+#define  PAD_TOL_SHIFT		25
+#define  PAD_TOL_MASK		0x1
+#define  PAD_TOL_3V3		0	/* 3.3V default */
+#define  PAD_TOL_1V8		1	/* 1.8V tolerant */
 
 #define GPI_GPE_STS_OFFSET	0x140
 #define GPI_GPE_EN_OFFSET	0x160