mmc: atmel-mci: fix burst/chunk size modification

The use of DMA slave config operation requires that the burst size
(aka chunk size) is specified through this interface.
Modify atmel-mci slave driver to use this specification on its side.

Signed-off-by: Nicolas Ferre <[e-mail]>
Signed-off-by: Ludovic Desroches <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/host/atmel-mci-regs.h

···
 #define atmci_writel(port,reg,value)			\
 	__raw_writel((value), (port)->regs + reg)
 
+/*
+ * Fix sconfig's burst size according to atmel MCI. We need to convert them as:
+ * 1 -> 0, 4 -> 1, 8 -> 2, 16 -> 3.
+ *
+ * This can be done by finding most significant bit set.
+ */
+static inline unsigned int atmci_convert_chksize(unsigned int maxburst)
+{
+	if (maxburst > 1)
+		return fls(maxburst) - 2;
+	else
+		return 0;
+}
+
 #endif /* __DRIVERS_MMC_ATMEL_MCI_H__ */

drivers/mmc/host/atmel-mci.c

···
 	enum dma_data_direction		direction;
 	enum dma_transfer_direction	slave_dirn;
 	unsigned int			sglen;
+	u32				maxburst;
 	u32 iflags;
 
 	data->error = -EINPROGRESS;
···
 	if (!chan)
 		return -ENODEV;
 
-	if (host->caps.has_dma)
-		atmci_writel(host, ATMCI_DMA, ATMCI_DMA_CHKSIZE(3) | ATMCI_DMAEN);
-
 	if (data->flags & MMC_DATA_READ) {
 		direction = DMA_FROM_DEVICE;
 		host->dma_conf.direction = slave_dirn = DMA_DEV_TO_MEM;
+		maxburst = atmci_convert_chksize(host->dma_conf.src_maxburst);
 	} else {
 		direction = DMA_TO_DEVICE;
 		host->dma_conf.direction = slave_dirn = DMA_MEM_TO_DEV;
+		maxburst = atmci_convert_chksize(host->dma_conf.dst_maxburst);
 	}
+
+	atmci_writel(host, ATMCI_DMA, ATMCI_DMA_CHKSIZE(maxburst) | ATMCI_DMAEN);
 
 	sglen = dma_map_sg(chan->device->dev, data->sg,
 			data->sg_len, direction);