mv_xor: support big endian systems using descriptor swap feature

The mv_xor driver had never been used in a big-endian context, and
therefore was not using the hardware features to support such an
execution environment. The hardware provides a "descriptor swap" bit
that automatically swaps the bytes of the DMA descriptors, within
blocks of 8 bytes. This requires a different DMA descriptor layout on
big-endian systems, as well as enabling this "descriptor swap" bit.

This mechanism is exactly identical to the one already used in the
mv643xx_eth network driver and the mvneta network driver.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Dan Williams <djbw@fb.com>

2 files changed, 36 insertions, 3 deletions

diff --git a/drivers/dma/mv_xor.c b/drivers/dma/mv_xor.c
index c026b27f76e1..d332b9e3f9ce 100644
--- a/drivers/dma/mv_xor.c
+++ b/drivers/dma/mv_xor.c
@@ -64,7 +64,7 @@ static u32 mv_desc_get_src_addr(struct mv_xor_desc_slot *desc,
                                 int src_idx)
 {
         struct mv_xor_desc *hw_desc = desc->hw_desc;
-        return hw_desc->phy_src_addr[src_idx];
+        return hw_desc->phy_src_addr[mv_phy_src_idx(src_idx)];
 }
 
 
@@ -107,7 +107,7 @@ static void mv_desc_set_src_addr(struct mv_xor_desc_slot *desc,
                                  int index, dma_addr_t addr)
 {
         struct mv_xor_desc *hw_desc = desc->hw_desc;
-        hw_desc->phy_src_addr[index] = addr;
+        hw_desc->phy_src_addr[mv_phy_src_idx(index)] = addr;
         if (desc->type == DMA_XOR)
                 hw_desc->desc_command |= (1 << index);
 }
@@ -192,6 +192,13 @@ static void mv_set_mode(struct mv_xor_chan *chan,
 
         config &= ~0x7;
         config |= op_mode;
+
+#if defined(__BIG_ENDIAN)
+        config |= XOR_DESCRIPTOR_SWAP;
+#else
+        config &= ~XOR_DESCRIPTOR_SWAP;
+#endif
+
         writel_relaxed(config, XOR_CONFIG(chan));
         chan->current_type = type;
 }
diff --git a/drivers/dma/mv_xor.h b/drivers/dma/mv_xor.h
index c619359cb7fe..06b067f24c9b 100644
--- a/drivers/dma/mv_xor.h
+++ b/drivers/dma/mv_xor.h
@@ -29,8 +29,10 @@
 #define MV_XOR_THRESHOLD                1
 #define MV_XOR_MAX_CHANNELS             2
 
+/* Values for the XOR_CONFIG register */
 #define XOR_OPERATION_MODE_XOR          0
 #define XOR_OPERATION_MODE_MEMCPY       2
+#define XOR_DESCRIPTOR_SWAP             BIT(14)
 
 #define XOR_CURR_DESC(chan)     (chan->mmr_base + 0x210 + (chan->idx * 4))
 #define XOR_NEXT_DESC(chan)     (chan->mmr_base + 0x200 + (chan->idx * 4))
@@ -143,7 +145,16 @@ struct mv_xor_desc_slot {
 #endif
 };
 
-/* This structure describes XOR descriptor size 64bytes */
+/*
+ * This structure describes XOR descriptor size 64bytes. The
+ * mv_phy_src_idx() macro must be used when indexing the values of the
+ * phy_src_addr[] array. This is due to the fact that the 'descriptor
+ * swap' feature, used on big endian systems, swaps descriptors data
+ * within blocks of 8 bytes. So two consecutive values of the
+ * phy_src_addr[] array are actually swapped in big-endian, which
+ * explains the different mv_phy_src_idx() implementation.
+ */
+#if defined(__LITTLE_ENDIAN)
 struct mv_xor_desc {
         u32 status;             /* descriptor execution status */
         u32 crc32_result;       /* result of CRC-32 calculation */
@@ -155,6 +166,21 @@ struct mv_xor_desc {
         u32 reserved0;
         u32 reserved1;
 };
+#define mv_phy_src_idx(src_idx) (src_idx)
+#else
+struct mv_xor_desc {
+        u32 crc32_result;       /* result of CRC-32 calculation */
+        u32 status;             /* descriptor execution status */
+        u32 phy_next_desc;      /* next descriptor address pointer */
+        u32 desc_command;       /* type of operation to be carried out */
+        u32 phy_dest_addr;      /* destination block address */
+        u32 byte_count;         /* size of src/dst blocks in bytes */
+        u32 phy_src_addr[8];    /* source block addresses */
+        u32 reserved1;
+        u32 reserved0;
+};
+#define mv_phy_src_idx(src_idx) (src_idx ^ 1)
+#endif
 
 #define to_mv_sw_desc(addr_hw_desc)             \
         container_of(addr_hw_desc, struct mv_xor_desc_slot, hw_desc)