drivers: dma_xmc4xxx: Use DAR instead of CTL.BLOCK_TS to set pending_length

When quering the DMA status we need to return the number of pending bytes
left in the transfer. Currently this is inferred by calling
XMC_DMA_CH_GetTransferredData(). However, this function actually returns
the number of items read from the source peripheral (via CTL.BLOCK_TS).
It doesn't guarantee that the last item was fully transferred to the
destination.

When using the ADDR_ADJ_INCREMENT/DECREMENT options it is better to use
DAR register to infer the number of transferred bytes. This points to the
memory address where the next data will be written. It only increments
after the ongoing transfer from source to destination is completed.

Signed-off-by: Andriy Gelman <[email protected]>

Author: talih0

drivers/dma/dma_xmc4xxx.c

@@ -32,9 +32,12 @@ LOG_MODULE_REGISTER(dma_xmc4xxx, CONFIG_DMA_LOG_LEVEL);
 struct dma_xmc4xxx_channel {
 	dma_callback_t cb;
 	void *user_data;
+	uint32_t dest_address;
 	uint16_t block_ts;
 	uint8_t source_data_size;
 	uint8_t dlr_line;
+	uint8_t channel_direction;
+	uint8_t dest_addr_adj;
 };
 
 struct dma_xmc4xxx_config {
@@ -62,7 +65,7 @@ do {
 		if (dma_channel->cb) {                                                     \
 			dma_channel->cb(dev, dma_channel->user_data, channel, (ret));      \
 		}                                                                          \
-}                                                                                          \
+	}                                                                                  \
 } while (0)
 
 /* Isr is level triggered, so we don't have to loop over all the channels */
@@ -287,6 +290,9 @@ static int dma_xmc4xxx_config(const struct device *dev, uint32_t channel, struct
 	dev_data->channels[channel].block_ts = block->block_size / config->source_data_size;
 	dev_data->channels[channel].source_data_size = config->source_data_size;
 	dev_data->channels[channel].dlr_line = dlr_line;
+	dev_data->channels[channel].channel_direction = config->channel_direction;
+	dev_data->channels[channel].dest_addr_adj = block->dest_addr_adj;
+	dev_data->channels[channel].dest_address = block->dest_address;
 
 	XMC_DMA_CH_DisableEvent(dma, channel, ALL_EVENTS);
 	XMC_DMA_CH_EnableEvent(dma, channel, XMC_DMA_CH_EVENT_TRANSFER_COMPLETE);
@@ -368,6 +374,7 @@ static int dma_xmc4xxx_reload(const struct device *dev, uint32_t channel, uint32
 		return -EINVAL;
 	}
 	dma_channel->block_ts = block_ts;
+	dma_channel->dest_address = dst;
 
 	/* do we need to clear any errors */
 	dma->CH[channel].SAR = src;
@@ -384,6 +391,7 @@ static int dma_xmc4xxx_get_status(const struct device *dev, uint32_t channel,
 	const struct dma_xmc4xxx_config *dev_cfg = dev->config;
 	XMC_DMA_t *dma = dev_cfg->dma;
 	struct dma_xmc4xxx_channel *dma_channel;
+	uint32_t transferred_bytes;
 
 	if (channel >= dev_data->ctx.dma_channels) {
 		LOG_ERR("Invalid channel number");
@@ -393,8 +401,20 @@ static int dma_xmc4xxx_get_status(const struct device *dev, uint32_t channel,
 
 	stat->busy = XMC_DMA_CH_IsEnabled(dma, channel);
 
-	stat->pending_length  = dma_channel->block_ts - XMC_DMA_CH_GetTransferredData(dma, channel);
-	stat->pending_length *= dma_channel->source_data_size;
+	/* Use DAR to check for transferred bytes when possible. Value CTL.BLOCK_TS does not */
+	/* appear to guarantee that the last value is fully transferred to dest. */
+	if (dma_channel->dest_addr_adj == DMA_ADDR_ADJ_INCREMENT) {
+		transferred_bytes = dma->CH[channel].DAR - dma_channel->dest_address;
+		stat->pending_length = dma_channel->block_ts - transferred_bytes;
+	} else if (dma_channel->dest_addr_adj == DMA_ADDR_ADJ_DECREMENT) {
+		transferred_bytes =  dma_channel->dest_address - dma->CH[channel].DAR;
+		stat->pending_length = dma_channel->block_ts - transferred_bytes;
+	} else {
+		transferred_bytes = XMC_DMA_CH_GetTransferredData(dma, channel);
+		stat->pending_length = dma_channel->block_ts - transferred_bytes;
+		stat->pending_length *= dma_channel->source_data_size;
+	}
+
 	/* stat->dir and other remaining fields are not set. They are not */
 	/* useful for xmc4xxx peripheral drivers. */