ALSA: oxygen: add UART I/O functions

Add functions to allow model drivers to communicate with external chips
by doing I/O with the not-used-for-MIDI UART.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

sound/pci/oxygen/oxygen.h

@@ -79,6 +79,7 @@ struct oxygen_model {
 	void (*update_dac_volume)(struct oxygen *chip);
 	void (*update_dac_mute)(struct oxygen *chip);
 	void (*gpio_changed)(struct oxygen *chip);
+	void (*uart_input)(struct oxygen *chip);
 	void (*ac97_switch)(struct oxygen *chip,
 			    unsigned int reg, unsigned int mute);
 	const unsigned int *dac_tlv;
@@ -125,6 +126,8 @@ struct oxygen {
 		__le32 _32[OXYGEN_IO_SIZE / 4];
 	} saved_registers;
 	u16 saved_ac97_registers[2][0x40];
+	unsigned int uart_input_count;
+	u8 uart_input[32];
 	struct oxygen_model model;
 };
 
@@ -174,6 +177,9 @@ void oxygen_write_ac97_masked(struct oxygen *chip, unsigned int codec,
 void oxygen_write_spi(struct oxygen *chip, u8 control, unsigned int data);
 void oxygen_write_i2c(struct oxygen *chip, u8 device, u8 map, u8 data);
 
+void oxygen_reset_uart(struct oxygen *chip);
+void oxygen_write_uart(struct oxygen *chip, u8 data);
+
 static inline void oxygen_set_bits8(struct oxygen *chip,
 				    unsigned int reg, u8 value)
 {

sound/pci/oxygen/oxygen_io.c

@@ -20,6 +20,7 @@
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <sound/core.h>
+#include <sound/mpu401.h>
 #include <asm/io.h>
 #include "oxygen.h"
 
@@ -232,3 +233,23 @@ void oxygen_write_i2c(struct oxygen *chip, u8 device, u8 map, u8 data)
 		      device | OXYGEN_2WIRE_DIR_WRITE);
 }
 EXPORT_SYMBOL(oxygen_write_i2c);
+
+static void _write_uart(struct oxygen *chip, unsigned int port, u8 data)
+{
+	if (oxygen_read8(chip, OXYGEN_MPU401 + 1) & MPU401_TX_FULL)
+		msleep(1);
+	oxygen_write8(chip, OXYGEN_MPU401 + port, data);
+}
+
+void oxygen_reset_uart(struct oxygen *chip)
+{
+	_write_uart(chip, 1, MPU401_RESET);
+	_write_uart(chip, 1, MPU401_ENTER_UART);
+}
+EXPORT_SYMBOL(oxygen_reset_uart);
+
+void oxygen_write_uart(struct oxygen *chip, u8 data)
+{
+	_write_uart(chip, 0, data);
+}
+EXPORT_SYMBOL(oxygen_write_uart);

sound/pci/oxygen/oxygen_lib.c

@@ -35,6 +35,30 @@ MODULE_DESCRIPTION("C-Media CMI8788 helper library");
 MODULE_LICENSE("GPL v2");
 
 
+static inline int oxygen_uart_input_ready(struct oxygen *chip)
+{
+	return !(oxygen_read8(chip, OXYGEN_MPU401 + 1) & MPU401_RX_EMPTY);
+}
+
+static void oxygen_read_uart(struct oxygen *chip)
+{
+	if (unlikely(!oxygen_uart_input_ready(chip))) {
+		/* no data, but read it anyway to clear the interrupt */
+		oxygen_read8(chip, OXYGEN_MPU401);
+		return;
+	}
+	do {
+		u8 data = oxygen_read8(chip, OXYGEN_MPU401);
+		if (data == MPU401_ACK)
+			continue;
+		if (chip->uart_input_count >= ARRAY_SIZE(chip->uart_input))
+			chip->uart_input_count = 0;
+		chip->uart_input[chip->uart_input_count++] = data;
+	} while (oxygen_uart_input_ready(chip));
+	if (chip->model.uart_input)
+		chip->model.uart_input(chip);
+}
+
 static irqreturn_t oxygen_interrupt(int dummy, void *dev_id)
 {
 	struct oxygen *chip = dev_id;
@@ -87,8 +111,12 @@ static irqreturn_t oxygen_interrupt(int dummy, void *dev_id)
 	if (status & OXYGEN_INT_GPIO)
 		schedule_work(&chip->gpio_work);
 
-	if ((status & OXYGEN_INT_MIDI) && chip->midi)
-		snd_mpu401_uart_interrupt(0, chip->midi->private_data);
+	if (status & OXYGEN_INT_MIDI) {
+		if (chip->midi)
+			snd_mpu401_uart_interrupt(0, chip->midi->private_data);
+		else
+			oxygen_read_uart(chip);
+	}
 
 	if (status & OXYGEN_INT_AC97)
 		wake_up(&chip->ac97_waitqueue);