[Qemu-devel] [PATCH 07/17] imx_fec: Emulate SHIFT16 in ENETx_RACC

[Andrey Smirnov]

Needed to support latest Linux kernel driver which relies on that
functionality.

Cc: Peter Maydell <address@hidden>
Cc: Jason Wang <address@hidden>
Cc: address@hidden
Cc: address@hidden
Cc: address@hidden
Signed-off-by: Andrey Smirnov <address@hidden>
---
 hw/net/imx_fec.c         | 23 +++++++++++++++++++++++
 include/hw/net/imx_fec.h |  2 ++
 2 files changed, 25 insertions(+)

diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c
index 8a77136d38..bd62d7a75f 100644
--- a/hw/net/imx_fec.c
+++ b/hw/net/imx_fec.c
@@ -1037,6 +1037,7 @@ static ssize_t imx_enet_receive(NetClientState *nc, const 
uint8_t *buf,
     uint32_t buf_addr;
     unsigned int buf_len;
     size_t size = len;
+    bool shift16 = s->regs[ENET_RACC] & ENET_RACC_SHIFT16;
 
     FEC_PRINTF("len %d\n", (int)size);
 
@@ -1049,6 +1050,10 @@ static ssize_t imx_enet_receive(NetClientState *nc, 
const uint8_t *buf,
     /* 4 bytes for the CRC.  */
     size += 4;
 
+    if (shift16) {
+        size += 2;
+    }
+
     /* Huge frames are truncted.  */
     if (size > s->regs[ENET_FTRL]) {
         size = s->regs[ENET_FTRL];
@@ -1085,6 +1090,24 @@ static ssize_t imx_enet_receive(NetClientState *nc, 
const uint8_t *buf,
             buf_len += size - 4;
         }
         buf_addr = bd.data;
+
+        if (shift16) {
+            /*
+             * If SHIFT16 bit of ENETx_RACC register is set we need to
+             * align the payload to 4-byte boundary.
+             */
+            const uint8_t zeros[2] = { 0 };
+
+            dma_memory_write(&address_space_memory, buf_addr,
+                             zeros, sizeof(zeros));
+
+            buf_addr += sizeof(zeros);
+            buf_len  -= sizeof(zeros);
+
+            shift16 = false; /* We only do this once per Ethernet
+                              * frame */
+        }
+
         dma_memory_write(&address_space_memory, buf_addr, buf, buf_len);
         buf += buf_len;
         if (size < 4) {
diff --git a/include/hw/net/imx_fec.h b/include/hw/net/imx_fec.h
index 4bc8f03ec2..20a6aa98b4 100644
--- a/include/hw/net/imx_fec.h
+++ b/include/hw/net/imx_fec.h
@@ -169,6 +169,8 @@
 #define ENET_TWFR_TFWR_LENGTH  (6)
 #define ENET_TWFR_STRFWD       (1 << 8)
 
+#define ENET_RACC_SHIFT16      BIT(7)
+
 /* Buffer Descriptor.  */
 typedef struct {
     uint16_t length;
-- 
2.13.5