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>

1 files changed, 30 insertions, 2 deletions

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);