mips: add support for noncached_alloc()

This patch adds support for noncached_alloc() which was only supported by
ARM platform.

Unlike the ARM platform, MMU is not used in u-boot for MIPS. Instead, KSEG
is provided to access uncached memory. So most code of this patch is copied
from cache.c of ARM platform, with only two differences:
1. MMU is untouched in noncached_set_region()
2. Address returned by noncached_alloc() is converted using KSEG1ADDR()

Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>

arch/mips/include/asm/system.h

@@ -282,4 +282,24 @@ static inline void instruction_hazard_barrier(void)
 	: "=&r"(tmp));
 }
 
+#ifdef CONFIG_SYS_NONCACHED_MEMORY
+/* 1MB granularity */
+#define MMU_SECTION_SHIFT	20
+#define MMU_SECTION_SIZE	(1 << MMU_SECTION_SHIFT)
+
+/**
+ * noncached_init() - Initialize non-cached memory region
+ *
+ * Initialize non-cached memory area. This memory region will be typically
+ * located right below the malloc() area and be accessed from KSEG1.
+ *
+ * It is called during the generic post-relocation init sequence.
+ *
+ * Return: 0 if OK
+ */
+int noncached_init(void);
+
+phys_addr_t noncached_alloc(size_t size, size_t align);
+#endif /* CONFIG_SYS_NONCACHED_MEMORY */
+
 #endif /* _ASM_SYSTEM_H */

arch/mips/lib/cache.c

@@ -6,6 +6,7 @@
 
 #include <common.h>
 #include <cpu_func.h>
+#include <malloc.h>
 #include <asm/cache.h>
 #include <asm/cacheops.h>
 #include <asm/cm.h>
@@ -197,3 +198,45 @@ void dcache_disable(void)
 	/* ensure the pipeline doesn't contain now-invalid instructions */
 	instruction_hazard_barrier();
 }
+
+#ifdef CONFIG_SYS_NONCACHED_MEMORY
+static unsigned long noncached_start;
+static unsigned long noncached_end;
+static unsigned long noncached_next;
+
+void noncached_set_region(void)
+{
+}
+
+int noncached_init(void)
+{
+	phys_addr_t start, end;
+	size_t size;
+
+	/* If this calculation changes, update board_f.c:reserve_noncached() */
+	end = ALIGN(mem_malloc_start, MMU_SECTION_SIZE) - MMU_SECTION_SIZE;
+	size = ALIGN(CONFIG_SYS_NONCACHED_MEMORY, MMU_SECTION_SIZE);
+	start = end - size;
+
+	debug("mapping memory %pa-%pa non-cached\n", &start, &end);
+
+	noncached_start = start;
+	noncached_end = end;
+	noncached_next = start;
+
+	return 0;
+}
+
+phys_addr_t noncached_alloc(size_t size, size_t align)
+{
+	phys_addr_t next = ALIGN(noncached_next, align);
+
+	if (next >= noncached_end || (noncached_end - next) < size)
+		return 0;
+
+	debug("allocated %zu bytes of uncached memory @%pa\n", size, &next);
+	noncached_next = next + size;
+
+	return CKSEG1ADDR(next);
+}
+#endif /* CONFIG_SYS_NONCACHED_MEMORY */