altos/avr: SPI mutex is now held by the caller, not the SPI driver

SPI transactions generally require a read followed by a write, with
the chip select held the whole time. As a result, the SPI bus must be
held across multiple transactions. To make this reliable, the caller
must hold the SPI mutex, instead of the underlying SPI driver.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/avr/ao_spi_usart.c b/src/avr/ao_spi_usart.c
index 6ed708ff38faf9d09e3eb44ff13ee33aea3bc5ee..1996fcd9e98a9cee798aaaf3ace662c2b623924a 100644 (file)
--- a/src/avr/ao_spi_usart.c
+++ b/src/avr/ao_spi_usart.c
@@ -33,14 +33,12 @@ ao_spi_send(void __xdata *block, uint16_t len) __reentrant
 {
        uint8_t *d = block;
 
-       ao_mutex_get(&ao_spi_mutex);
        while (len--) {
                while (!(UCSR1A & (1 << UDRE1)));
                UDR1 = *d++;
                while (!(UCSR1A & (1 << RXC1)));
                (void) UDR1;
        }
-       ao_mutex_put(&ao_spi_mutex);
 }
 
 /* Receive bytes over SPI.
@@ -54,14 +52,12 @@ ao_spi_recv(void __xdata *block, uint16_t len) __reentrant
 {
        uint8_t *d = block;
 
-       ao_mutex_get(&ao_spi_mutex);
        while (len--) {
                while (!(UCSR1A & (1 << UDRE1)));
                UDR1 = 0;
                while (!(UCSR1A & (1 << RXC1)));
                *d++ = UDR1;
        }
-       ao_mutex_put(&ao_spi_mutex);
 }
 
 /*