ec/kontron/kempld: Add minimal GPIO driver

The patch adds an interface for configuring GPIOs inside the Kontron
CPLD/EC. This allows to statically define the mode for each GPIO pin
in devicetree.cb of the motherboard or carrier board. For example:

chip ec/kontron/kempld
	device gpio 0 on
		register "gpio[0]"  = "KEMPLD_GPIO_INPUT"
		register "gpio[4]"  = "KEMPLD_GPIO_OUTPUT_LOW"
		register "gpio[5]"  = "KEMPLD_GPIO_OUTPUT_HIGH"
		register "gpio[11]" = "KEMPLD_GPIO_DEFAULT"
	end
end

In this case, <device gpio 0>, like all other devices, is not a real
device inside the EC. These definitions are used to understand the EC
resources and systematize configuration options, but if mark this as
<off>, the initialization step will be skipped in the driver code.

Use KEMPLD_GPIO_DEFAULT or skip it in devicetree.cb to not configure
the GPIO and keep the default mode after CPLD reset.

This work is based on code from the drivers/gpio/gpio-kempld.c linux
driver. Tested on Kontron mAL-10 COMe module [1].

[1] CB:54380 , Change-Id: I7d354aa32ac8c64f54b2bcbdb4f1b8915f55264e

Change-Id: Id767aa451fbf2ca1c0dccfc9aa2c024c6f37c1bb
Signed-off-by: Maxim Polyakov <max.senia.poliak@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47595
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

5 files changed, 95 insertions, 1 deletions

diff --git a/src/ec/kontron/kempld/Makefile.inc b/src/ec/kontron/kempld/Makefile.inc
index 0d5988625e..e7bafa39e7 100644
--- a/src/ec/kontron/kempld/Makefile.inc
+++ b/src/ec/kontron/kempld/Makefile.inc
@@ -2,3 +2,4 @@ bootblock-$(CONFIG_EC_KONTRON_KEMPLD) += early_kempld.c
 ramstage-$(CONFIG_EC_KONTRON_KEMPLD) += early_kempld.c
 ramstage-$(CONFIG_EC_KONTRON_KEMPLD) += kempld.c
 ramstage-$(CONFIG_EC_KONTRON_KEMPLD) += kempld_i2c.c
+ramstage-$(CONFIG_EC_KONTRON_KEMPLD) += kempld_gpio.c
diff --git a/src/ec/kontron/kempld/chip.h b/src/ec/kontron/kempld/chip.h
index 30f40fe097..c44a103182 100644
--- a/src/ec/kontron/kempld/chip.h
+++ b/src/ec/kontron/kempld/chip.h
@@ -3,7 +3,15 @@
 #ifndef EC_KONTRON_KEMPLD_CHIP_H
 #define EC_KONTRON_KEMPLD_CHIP_H
 
-#define KEMPLD_NUM_UARTS 2
+#define KEMPLD_NUM_UARTS	2
+#define KEMPLD_NUM_GPIOS	16
+
+enum kempld_gpio_mode {
+	KEMPLD_GPIO_DEFAULT = 0,
+	KEMPLD_GPIO_INPUT,
+	KEMPLD_GPIO_OUTPUT_LOW,
+	KEMPLD_GPIO_OUTPUT_HIGH,
+};
 
 enum kempld_uart_io {
 	KEMPLD_UART_3F8 = 0,
@@ -26,6 +34,7 @@ struct kempld_uart {
 
 struct ec_kontron_kempld_config {
 	struct kempld_uart uart[KEMPLD_NUM_UARTS];
+	enum kempld_gpio_mode gpio[KEMPLD_NUM_GPIOS];
 	unsigned short i2c_frequency;
 };
 
diff --git a/src/ec/kontron/kempld/kempld.c b/src/ec/kontron/kempld/kempld.c
index f8371a8d82..0489bac042 100644
--- a/src/ec/kontron/kempld/kempld.c
+++ b/src/ec/kontron/kempld/kempld.c
@@ -93,6 +93,14 @@ static void kempld_enable_dev(struct device *const dev)
 			printk(BIOS_WARNING, "KEMPLD: Spurious device %s.\n", dev_path(dev));
 			break;
 		}
+	} else if (dev->path.type == DEVICE_PATH_GPIO) {
+		if (dev->path.gpio.id == 0) {
+			if (kempld_gpio_pads_config(dev) < 0)
+				printk(BIOS_ERR, "KEMPLD: GPIO configuration failed!\n");
+		} else {
+			printk(BIOS_WARNING, "KEMPLD: Spurious GPIO device %s.\n",
+			       dev_path(dev));
+		}
 	}
 }
 
diff --git a/src/ec/kontron/kempld/kempld_gpio.c b/src/ec/kontron/kempld/kempld_gpio.c
new file mode 100644
index 0000000000..8699c1f477
--- /dev/null
+++ b/src/ec/kontron/kempld/kempld_gpio.c
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <stdint.h>
+#include <arch/io.h>
+#include <delay.h>
+#include "chip.h"
+#include "kempld.h"
+#include "kempld_internal.h"
+
+enum kempld_gpio_direction {
+	KEMPLD_GPIO_DIR_IN  = 0,
+	KEMPLD_GPIO_DIR_OUT = 1
+};
+
+static void kempld_gpio_value_set(u8 pin_num, u8 value)
+{
+	const u8 mask = KEMPLD_GPIO_MASK(pin_num);
+	u8 reg_val = kempld_read8(KEMPLD_GPIO_LVL(pin_num));
+	reg_val = value ? reg_val | mask : reg_val & ~mask;
+	kempld_write8(KEMPLD_GPIO_LVL(pin_num), reg_val);
+}
+
+static void kempld_gpio_direction_set(u8 pin_num, enum kempld_gpio_direction dir)
+{
+	const u8 mask = KEMPLD_GPIO_MASK(pin_num);
+	u8 reg_val = kempld_read8(KEMPLD_GPIO_DIR(pin_num));
+	reg_val = dir == KEMPLD_GPIO_DIR_OUT ? reg_val | mask : reg_val & ~mask;
+	kempld_write8(KEMPLD_GPIO_DIR(pin_num), reg_val);
+}
+
+static int kempld_configure_gpio(u8 pin_num, enum kempld_gpio_mode mode)
+{
+	if (kempld_get_mutex(100) < 0)
+		return -1;
+
+	switch (mode) {
+	case KEMPLD_GPIO_DEFAULT:
+		break;
+
+	case KEMPLD_GPIO_INPUT:
+		kempld_gpio_direction_set(pin_num, KEMPLD_GPIO_DIR_IN);
+		break;
+
+	case KEMPLD_GPIO_OUTPUT_LOW:
+		kempld_gpio_value_set(pin_num, 0);
+		kempld_gpio_direction_set(pin_num, KEMPLD_GPIO_DIR_OUT);
+		break;
+
+	case KEMPLD_GPIO_OUTPUT_HIGH:
+		kempld_gpio_value_set(pin_num, 1);
+		kempld_gpio_direction_set(pin_num, KEMPLD_GPIO_DIR_OUT);
+		break;
+	}
+
+	kempld_release_mutex();
+	return 0;
+}
+
+int kempld_gpio_pads_config(struct device *dev)
+{
+	const struct ec_kontron_kempld_config *config = dev->chip_info;
+
+	if (!config)
+		return -1;
+
+	for (u8 i = 0; i < KEMPLD_NUM_GPIOS; ++i) {
+		if (kempld_configure_gpio(i, config->gpio[i]) < 0)
+			return -1;
+	}
+	return 0;
+}
diff --git a/src/ec/kontron/kempld/kempld_internal.h b/src/ec/kontron/kempld/kempld_internal.h
index 993fe8edd1..2c64f7946b 100644
--- a/src/ec/kontron/kempld/kempld_internal.h
+++ b/src/ec/kontron/kempld/kempld_internal.h
@@ -28,6 +28,11 @@
 
 #define KEMPLD_CLK 33333333 /* 33MHz */
 
+#define KEMPLD_GPIO_MASK(pin_num)	(1 << ((pin_num) % 8))
+#define KEMPLD_GPIO_DIR(pin_num)	(0x40 + (pin_num) / 8)
+#define KEMPLD_GPIO_LVL(pin_num)	(0x42 + (pin_num) / 8)
+
 void kempld_i2c_device_init(struct device *const dev);
+int kempld_gpio_pads_config(struct device *dev);
 
 #endif /* EC_KONTRON_KEMPLD_INTERNAL_H */