[Qemu-devel] [PATCH v2 06/12] xilinx_spips: Update striping to be big-endian bit order

[Francisco Iglesias <frasse.iglesias@gmail.com>]

Update striping functionality to be big-endian bit order and output even
bits into lower memory and odd bits into upper.

Signed-off-by: Francisco Iglesias <frasse.iglesias@gmail.com>
---
 hw/ssi/xilinx_spips.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
index 93b9e43..d052fc6 100644
--- a/hw/ssi/xilinx_spips.c
+++ b/hw/ssi/xilinx_spips.c
@@ -209,14 +209,14 @@ static void xilinx_spips_reset(DeviceState *d)
     xilinx_spips_update_cs_lines(s);
 }
 
-/* N way (num) in place bit striper. Lay out row wise bits (LSB to MSB)
+/* N way (num) in place bit striper. Lay out row wise bits (MSB to LSB)
  * column wise (from element 0 to N-1). num is the length of x, and dir
  * reverses the direction of the transform. Best illustrated by example:
  * Each digit in the below array is a single bit (num == 3):
  *
- * {{ 76543210, }  ----- stripe (dir == false) -----> {{ FCheb630, }
- *  { hgfedcba, }                                      { GDAfc741, }
- *  { HGFEDCBA, }} <---- upstripe (dir == true) -----  { HEBgda52, }}
+ * {{ 76543210, }  ----- stripe (dir == false) -----> {{ 741gdaFC, }
+ *  { hgfedcba, }                                      { 630fcHEB, }
+ *  { HGFEDCBA, }} <---- upstripe (dir == true) -----  { 52hebGDA, }}
  */
 
 static inline void stripe8(uint8_t *x, int num, bool dir)
@@ -224,15 +224,15 @@ static inline void stripe8(uint8_t *x, int num, bool dir)
     uint8_t r[num];
     memset(r, 0, sizeof(uint8_t) * num);
     int idx[2] = {0, 0};
-    int bit[2] = {0, 0};
+    int bit[2] = {0, 7};
     int d = dir;
 
     for (idx[0] = 0; idx[0] < num; ++idx[0]) {
-        for (bit[0] = 0; bit[0] < 8; ++bit[0]) {
-            r[idx[d]] |= x[idx[!d]] & 1 << bit[!d] ? 1 << bit[d] : 0;
+        for (bit[0] = 7; bit[0] != -1; bit[0] += -1) {
+            r[idx[!d]] |= x[idx[d]] & 1 << bit[d] ? 1 << bit[!d] : 0;
             idx[1] = (idx[1] + 1) % num;
             if (!idx[1]) {
-                bit[1]++;
+                bit[1] += -1;
             }
         }
     }
@@ -267,8 +267,9 @@ static void xilinx_spips_flush_txfifo(XilinxSPIPS *s)
         }
 
         for (i = 0; i < num_effective_busses(s); ++i) {
+            int bus = num_effective_busses(s) - 1 - i;
             DB_PRINT_L(debug_level, "tx = %02x\n", tx_rx[i]);
-            tx_rx[i] = ssi_transfer(s->spi[i], (uint32_t)tx_rx[i]);
+            tx_rx[i] = ssi_transfer(s->spi[bus], (uint32_t)tx_rx[i]);
             DB_PRINT_L(debug_level, "rx = %02x\n", tx_rx[i]);
         }
 
-- 
2.9.3