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>

3 files changed, 57 insertions, 2 deletions

diff --git a/sound/pci/oxygen/oxygen.h b/sound/pci/oxygen/oxygen.h
index f82a96290f72..19107c6307e5 100644
--- a/sound/pci/oxygen/oxygen.h
+++ b/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)
 {
diff --git a/sound/pci/oxygen/oxygen_io.c b/sound/pci/oxygen/oxygen_io.c
index 83f135f80df4..deba7389aec3 100644
--- a/sound/pci/oxygen/oxygen_io.c
+++ b/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);
diff --git a/sound/pci/oxygen/oxygen_lib.c b/sound/pci/oxygen/oxygen_lib.c
index b1997216b4af..84f481d41efa 100644
--- a/sound/pci/oxygen/oxygen_lib.c
+++ b/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);