[PR 18] GRETH: added support for non-snooping GRETH 10/100 systems

[Daniel Hellstrom]

When data cache snooping is not present the cache needs
flushing, the SPARC LEON CPUs does not have to ability
to flush individual cache rows and flushing all cache is
expensive. Instead the LDA instruction is used to force
cache miss on individual loads during the IP-align copy
operation required anyway.

GRETH GBIT non-snooping systems are still unsupported,
since it use zero-copy (can deal with unaligned DMA).

Also, made the GRETH driver only built on LEON2/LEON3
platforms.

Signed-off-by: Daniel Hellstrom <daniel at gaisler.com>
---
 c/src/libchip/network/greth.c |   80 +++++++++++++++++++++++++++++++++++++---
 1 files changed, 74 insertions(+), 6 deletions(-)

diff --git a/c/src/libchip/network/greth.c b/c/src/libchip/network/greth.c
index b0e70b4..6af5283 100644
--- a/c/src/libchip/network/greth.c
+++ b/c/src/libchip/network/greth.c
@@ -12,10 +12,15 @@
  */
 
 #include <rtems.h>
-
-#define GRETH_SUPPORTED
 #include <bsp.h>
 
+/* This driver is only supported by the LEON BSPs */
+#if defined(LEON3) || defined(LEON2)
+  #define GRETH_SUPPORTED
+#endif
+
+#ifdef GRETH_SUPPORTED
+
 #include <inttypes.h>
 #include <errno.h>
 #include <rtems/bspIo.h>
@@ -57,6 +62,14 @@ extern rtems_isr_entry set_vector( rtems_isr_entry, rtems_vector_number, int );
 extern void ipalign(struct mbuf *m);
 #endif
 
+static inline unsigned int sparc_load_no_cache(unsigned int addr)
+{
+	unsigned int tmp;
+	asm volatile (" lda [%1] 1, %0\n" : "=r"(tmp) : "r"(addr) );
+	return tmp;
+}
+#define NO_CACHE_LOAD(addr) sparc_load_no_cache(addr)
+
 /*
  * Number of OCs supported by this driver
  */
@@ -499,6 +512,47 @@ auto_neg_done:
     print_init_info(sc);
 }
 
+#ifdef CPU_U32_FIX
+
+/*
+ * Routine to align the received packet so that the ip header
+ * is on a 32-bit boundary. Necessary for cpu's that do not
+ * allow unaligned loads and stores and when the 32-bit DMA
+ * mode is used.
+ *
+ * Transfers are done on word basis to avoid possibly slow byte
+ * and half-word writes.
+ */
+
+void ipalign(struct mbuf *m)
+{
+  unsigned int *first, *last, data;
+  unsigned int tmp = 0;
+
+  if ((((int) m->m_data) & 2) && (m->m_len)) {
+    last = (unsigned int *) ((((int) m->m_data) + m->m_len + 8) & ~3);
+    first = (unsigned int *) (((int) m->m_data) & ~3);
+		/* tmp = *first << 16; */
+		asm volatile (" lda [%1] 1, %0\n" : "=r"(tmp) : "r"(first) );
+		tmp = tmp << 16;
+    first++;
+    do {
+      /* When snooping is not available the LDA instruction must be used
+       * to avoid the cache to return an illegal value.
+       * Load with forced cache miss
+       * data = *first; 
+       */
+      asm volatile (" lda [%1] 1, %0\n" : "=r"(data) : "r"(first) );
+      *first = tmp | (data >> 16);
+      tmp = data << 16;
+      first++;
+    } while (first <= last);
+
+    m->m_data = (caddr_t)(((int) m->m_data) + 2);
+  }
+}
+#endif
+
 void
 greth_Daemon (void *arg)
 {
@@ -510,6 +564,8 @@ greth_Daemon (void *arg)
     rtems_event_set events;
     rtems_interrupt_level level;
     int first;
+    int tmp;
+    unsigned int addr;
 
     for (;;)
       {
@@ -539,7 +595,7 @@ greth_Daemon (void *arg)
     /* Scan for Received packets */
 again:
     while (!((len_status =
-		    dp->rxdesc[dp->rx_ptr].ctrl) & GRETH_RXD_ENABLE))
+		    NO_CACHE_LOAD(&dp->rxdesc[dp->rx_ptr].ctrl)) & GRETH_RXD_ENABLE))
 	    {
                     bad = 0;
                     if (len_status & GRETH_RXD_TOOLONG)
@@ -583,6 +639,17 @@ again:
                                     len - sizeof (struct ether_header);
 
                             eh = mtod (m, struct ether_header *);
+
+                            /* OVERRIDE CACHED ETHERNET HEADER FOR NON-SNOOPING SYSTEMS */
+                            addr = (unsigned int)eh;
+                            asm volatile (" lda [%1] 1, %0\n" : "=r"(tmp) : "r"(addr) );
+                            addr+=4;
+                            asm volatile (" lda [%1] 1, %0\n" : "=r"(tmp) : "r"(addr) );
+                            addr+=4;
+                            asm volatile (" lda [%1] 1, %0\n" : "=r"(tmp) : "r"(addr) );
+                            addr+=4;
+                            asm volatile (" lda [%1] 1, %0\n" : "=r"(tmp) : "r"(addr) );
+
                             m->m_data += sizeof (struct ether_header);
 #ifdef CPU_U32_FIX
                             if(!(dp->gbit_mac))
@@ -641,7 +708,7 @@ sendpacket (struct ifnet *ifp, struct mbuf *m)
     /*
      * Is there a free descriptor available?
      */
-    if ( dp->txdesc[dp->tx_ptr].ctrl & GRETH_TXD_ENABLE ){
+    if ( NO_CACHE_LOAD(&dp->txdesc[dp->tx_ptr].ctrl) & GRETH_TXD_ENABLE ){
             /* No. */
             inside = 0;
             return 1;
@@ -651,7 +718,7 @@ sendpacket (struct ifnet *ifp, struct mbuf *m)
     n = m;
 
     len = 0;
-    temp = (unsigned char *) dp->txdesc[dp->tx_ptr].addr;
+    temp = (unsigned char *) NO_CACHE_LOAD(&dp->txdesc[dp->tx_ptr].addr);
 #ifdef GRETH_DEBUG
     printf("TXD: 0x%08x : BUF: 0x%08x\n", (int) m->m_data, (int) temp);
 #endif
@@ -814,7 +881,7 @@ int greth_process_tx_gbit(struct greth_softc *sc)
      */
     for (;;){
         /* Reap Sent packets */
-        while((sc->tx_cnt > 0) && !(sc->txdesc[sc->tx_dptr].ctrl) && !(sc->txdesc[sc->tx_dptr].ctrl & GRETH_TXD_ENABLE)) {
+        while((sc->tx_cnt > 0) && !(NO_CACHE_LOAD(&sc->txdesc[sc->tx_dptr].ctrl) & GRETH_TXD_ENABLE)) {
             m_free(sc->txmbuf[sc->tx_dptr]);
             sc->tx_dptr = (sc->tx_dptr + 1) % sc->txbufs;
             sc->tx_cnt--;
@@ -1146,3 +1213,4 @@ rtems_greth_driver_attach (struct rtems_bsdnet_ifconfig *config,
     return 1;
 };
 
+#endif
-- 
1.7.0.4