drivers/pktmem: adjust allocPktBuf and freePktBuf

adjust packet buffer handling for targets with page size less than packet buffer size
JIRA: RTOS-507

drivers/pktmem.c

@@ -17,15 +17,24 @@
 #include <string.h>
 
 
+// FIXME: transfer to appropriate file with platform-specific definitions
+#if defined(__ARM_ARCH_7EM__)
+#define CACHE_LINE_SIZE 32
+#else
 #define CACHE_LINE_SIZE 64
-#define PAGE_SIZE       4096
+#endif
 
 #define TRUE_LRU 0
 
+#define PKT_BUF_SIZE (2048 - CACHE_LINE_SIZE)
+
+#if PAGE_SIZE < PKT_BUF_SIZE
+#define PKT_BUF_CNT 1
+#else
+#define PKT_BUF_CNT (size_t)((PAGE_SIZE - CACHE_LINE_SIZE) / PKT_BUF_SIZE)
+#define PKT_BUF_IDX 11 /* log2(PAGE_SIZE) - ceil(log2(PKT_BUF_CNT)) */
+#endif
 
-#define PKT_BUF_SIZE       (2048 - CACHE_LINE_SIZE)
-#define PKT_BUF_CNT        (size_t)((PAGE_SIZE - CACHE_LINE_SIZE) / PKT_BUF_SIZE)
-#define PKT_BUF_IDX        11 /* log2(PAGE_SIZE) - ceil(log2(PKT_BUF_CNT)) */
 #define PKT_BUF_CACHE_SIZE 16
 
 
@@ -65,7 +74,11 @@ static void net_listDel(buf_page_head_t *ph)
 static void net_freePktBuf(void *p)
 {
 	buf_page_head_t *ph = (void *)((uintptr_t)p & ~(PAGE_SIZE - 1));
+#if PAGE_SIZE < PKT_BUF_SIZE
+	unsigned which = 0;
+#else
 	unsigned which = ((size_t)p & (PAGE_SIZE - 1)) >> PKT_BUF_IDX;
+#endif
 	unsigned old_mask;
 
 	old_mask = ph->free_mask;
@@ -114,7 +127,11 @@ static ssize_t net_allocPktBuf(void **bufp)
 	if (pkt_bufs_free == 0) {
 		SYS_ARCH_UNPROTECT(old_level);
 
+#if PAGE_SIZE < PKT_BUF_SIZE
+		ph = dmammap(PKT_BUF_SIZE);
+#else
 		ph = dmammap(PAGE_SIZE);
+#endif
 		if (ph == NULL) {
 			printf("mmap: no memory?\n");
 			return 0;