altos/stm32f1: Grab both TX/RX DMA mutexes while doing I2C

The I2C engine appears to trigger an extra RX DMA transaction which
scrambles anything sharing the same DMA units.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

src/stm32f1/ao_arch_funcs.h

@@ -350,6 +350,12 @@ ao_dma_set_transfer(uint8_t 		index,
 		    uint16_t		count,
 		    uint32_t		ccr);
 
+void
+ao_dma_mutex_get(uint8_t index);
+
+void
+ao_dma_mutex_put(uint8_t index);
+
 void
 ao_dma_set_isr(uint8_t index, void (*isr)(int index));
 

src/stm32f1/ao_dma_stm.c

@@ -66,6 +66,27 @@ void stm_dma1_channel7_isr(void) { ao_dma_isr(STM_DMA_INDEX(7)); }
 static uint8_t ao_dma_active;
 #endif
 
+void
+ao_dma_mutex_get(uint8_t index)
+{
+	if (ao_dma_allocated[index]) {
+		if (ao_dma_mutex[index])
+			ao_panic(AO_PANIC_DMA);
+		ao_dma_mutex[index] = 0xff;
+	} else
+		ao_mutex_get(&ao_dma_mutex[index]);
+}
+
+void
+ao_dma_mutex_put(uint8_t index)
+{
+	if (ao_dma_allocated[index])
+		ao_dma_mutex[index] = 0;
+	else
+		ao_mutex_put(&ao_dma_mutex[index]);
+}
+
+
 void
 ao_dma_set_transfer(uint8_t 		index,
 		    volatile void	*peripheral,

src/stm32f1/ao_i2c_stm.c

@@ -224,11 +224,11 @@ ao_i2c_send(void *block, uint16_t len, uint8_t index, uint8_t stop)
 {
 	struct stm_i2c	*stm_i2c = ao_i2c_stm_info[index].stm_i2c;
 	uint8_t		tx_dma_index = ao_i2c_stm_info[index].tx_dma_index;
+	uint8_t		rx_dma_index = ao_i2c_stm_info[index].rx_dma_index;
 
 	/* Clear any pending ADDR bit */
 	(void) stm_i2c->sr2;
 	ao_i2c_wait_addr(index);
-	stm_i2c->cr2 = AO_STM_I2C_CR2 | (1 << STM_I2C_CR2_DMAEN);
 	ao_dma_set_transfer(tx_dma_index,
 			    &stm_i2c->dr,
 			    block,
@@ -241,13 +241,14 @@ ao_i2c_send(void *block, uint16_t len, uint8_t index, uint8_t stop)
 			    (0 << STM_DMA_CCR_PINC) |
 			    (0 << STM_DMA_CCR_CIRC) |
 			    (STM_DMA_CCR_DIR_MEM_TO_PER << STM_DMA_CCR_DIR));
+	ao_dma_mutex_get(rx_dma_index);
+	stm_i2c->cr2 = AO_STM_I2C_CR2 | (1 << STM_I2C_CR2_DMAEN);
 
 	ao_dma_start(tx_dma_index);
 	ao_arch_block_interrupts();
 	while (!ao_dma_done[tx_dma_index])
 		if (ao_sleep_for(&ao_dma_done[tx_dma_index], 1 + len))
 			break;
-	ao_dma_done_transfer(tx_dma_index);
 	stm_i2c->cr2 = AO_STM_I2C_CR2 | (1 << STM_I2C_CR2_ITEVTEN) | (1 << STM_I2C_CR2_ITERREN);
 	while ((stm_i2c->sr1 & (1 << STM_I2C_SR1_BTF)) == 0)
 		if (ao_sleep_for(&ao_i2c_state[index], 1 + len))
@@ -258,6 +259,8 @@ ao_i2c_send(void *block, uint16_t len, uint8_t index, uint8_t stop)
 		stm_i2c->cr1 = AO_STM_I2C_CR1 | (1 << STM_I2C_CR1_STOP);
 		ao_i2c_wait_stop(index);
 	}
+	ao_dma_mutex_put(rx_dma_index);
+	ao_dma_done_transfer(tx_dma_index);
 	return true;
 }
 
@@ -311,7 +314,9 @@ ao_i2c_recv(void *block, uint16_t len, uint8_t index, uint8_t stop)
 		ao_arch_release_interrupts();
 		ret = ao_i2c_recv_len[index] == 0;
 	} else {
+		uint8_t		tx_dma_index = ao_i2c_stm_info[index].tx_dma_index;
 		uint8_t		rx_dma_index = ao_i2c_stm_info[index].rx_dma_index;
+		ao_dma_mutex_get(tx_dma_index);
 		ao_dma_set_transfer(rx_dma_index,
 				    &stm_i2c->dr,
 				    block,
@@ -349,8 +354,9 @@ ao_i2c_recv(void *block, uint16_t len, uint8_t index, uint8_t stop)
 				break;
 		ao_arch_release_interrupts();
 		ret = ao_dma_done[rx_dma_index];
-		ao_dma_done_transfer(rx_dma_index);
 		stm_i2c->cr1 = AO_STM_I2C_CR1 | (1 << STM_I2C_CR1_STOP);
+		ao_dma_done_transfer(rx_dma_index);
+		ao_dma_mutex_put(tx_dma_index);
 	}
 	if (stop)
 		ao_i2c_wait_stop(index);