metag: Cache/TLB handling

Add cache and TLB handling code for metag, including the required
callbacks used by MM switches and DMA operations. Caches can be
partitioned between the hardware threads and the global space, however
this is usually configured by the bootloader so Linux doesn't make any
changes to this configuration. TLBs aren't configurable, so only need
consideration to flush them.

On Meta1 the L1 cache was VIVT which required a full flush on MM switch.
Meta2 has a VIPT L1 cache so it doesn't require the full flush on MM
switch. Meta2 can also have a writeback L2 with hardware prefetch which
requires some special handling. Support is optional, and the L2 can be
detected and initialised by Linux.

Signed-off-by: James Hogan <[email protected]>

arch/metag/include/asm/cache.h

@@ -0,0 +1,23 @@
+#ifndef __ASM_METAG_CACHE_H
+#define __ASM_METAG_CACHE_H
+
+/* L1 cache line size (64 bytes) */
+#define L1_CACHE_SHIFT		6
+#define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
+
+/* Meta requires large data items to be 8 byte aligned. */
+#define ARCH_SLAB_MINALIGN	8
+
+/*
+ * With an L2 cache, we may invalidate dirty lines, so we need to ensure DMA
+ * buffers have cache line alignment.
+ */
+#ifdef CONFIG_METAG_L2C
+#define ARCH_DMA_MINALIGN	L1_CACHE_BYTES
+#else
+#define ARCH_DMA_MINALIGN	8
+#endif
+
+#define __read_mostly __attribute__((__section__(".data..read_mostly")))
+
+#endif

arch/metag/include/asm/cacheflush.h

@@ -0,0 +1,250 @@
+#ifndef _METAG_CACHEFLUSH_H
+#define _METAG_CACHEFLUSH_H
+
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/io.h>
+
+#include <asm/l2cache.h>
+#include <asm/metag_isa.h>
+#include <asm/metag_mem.h>
+
+void metag_cache_probe(void);
+
+void metag_data_cache_flush_all(const void *start);
+void metag_code_cache_flush_all(const void *start);
+
+/*
+ * Routines to flush physical cache lines that may be used to cache data or code
+ * normally accessed via the linear address range supplied. The region flushed
+ * must either lie in local or global address space determined by the top bit of
+ * the pStart address. If Bytes is >= 4K then the whole of the related cache
+ * state will be flushed rather than a limited range.
+ */
+void metag_data_cache_flush(const void *start, int bytes);
+void metag_code_cache_flush(const void *start, int bytes);
+
+#ifdef CONFIG_METAG_META12
+
+/* Write through, virtually tagged, split I/D cache. */
+
+static inline void __flush_cache_all(void)
+{
+	metag_code_cache_flush_all((void *) PAGE_OFFSET);
+	metag_data_cache_flush_all((void *) PAGE_OFFSET);
+}
+
+#define flush_cache_all() __flush_cache_all()
+
+/* flush the entire user address space referenced in this mm structure */
+static inline void flush_cache_mm(struct mm_struct *mm)
+{
+	if (mm == current->mm)
+		__flush_cache_all();
+}
+
+#define flush_cache_dup_mm(mm) flush_cache_mm(mm)
+
+/* flush a range of addresses from this mm */
+static inline void flush_cache_range(struct vm_area_struct *vma,
+				     unsigned long start, unsigned long end)
+{
+	flush_cache_mm(vma->vm_mm);
+}
+
+static inline void flush_cache_page(struct vm_area_struct *vma,
+				    unsigned long vmaddr, unsigned long pfn)
+{
+	flush_cache_mm(vma->vm_mm);
+}
+
+#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE	1
+static inline void flush_dcache_page(struct page *page)
+{
+	metag_data_cache_flush_all((void *) PAGE_OFFSET);
+}
+
+#define flush_dcache_mmap_lock(mapping)		do { } while (0)
+#define flush_dcache_mmap_unlock(mapping)	do { } while (0)
+
+static inline void flush_icache_page(struct vm_area_struct *vma,
+				     struct page *page)
+{
+	metag_code_cache_flush(page_to_virt(page), PAGE_SIZE);
+}
+
+static inline void flush_cache_vmap(unsigned long start, unsigned long end)
+{
+	metag_data_cache_flush_all((void *) PAGE_OFFSET);
+}
+
+static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
+{
+	metag_data_cache_flush_all((void *) PAGE_OFFSET);
+}
+
+#else
+
+/* Write through, physically tagged, split I/D cache. */
+
+#define flush_cache_all()			do { } while (0)
+#define flush_cache_mm(mm)			do { } while (0)
+#define flush_cache_dup_mm(mm)			do { } while (0)
+#define flush_cache_range(vma, start, end)	do { } while (0)
+#define flush_cache_page(vma, vmaddr, pfn)	do { } while (0)
+#define flush_dcache_mmap_lock(mapping)		do { } while (0)
+#define flush_dcache_mmap_unlock(mapping)	do { } while (0)
+#define flush_icache_page(vma, pg)		do { } while (0)
+#define flush_cache_vmap(start, end)		do { } while (0)
+#define flush_cache_vunmap(start, end)		do { } while (0)
+
+#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE	1
+static inline void flush_dcache_page(struct page *page)
+{
+	/* FIXME: We can do better than this. All we are trying to do is
+	 * make the i-cache coherent, we should use the PG_arch_1 bit like
+	 * e.g. powerpc.
+	 */
+#ifdef CONFIG_SMP
+	metag_out32(1, SYSC_ICACHE_FLUSH);
+#else
+	metag_code_cache_flush_all((void *) PAGE_OFFSET);
+#endif
+}
+
+#endif
+
+/* Push n pages at kernel virtual address and clear the icache */
+static inline void flush_icache_range(unsigned long address,
+				      unsigned long endaddr)
+{
+#ifdef CONFIG_SMP
+	metag_out32(1, SYSC_ICACHE_FLUSH);
+#else
+	metag_code_cache_flush((void *) address, endaddr - address);
+#endif
+}
+
+static inline void flush_cache_sigtramp(unsigned long addr, int size)
+{
+	/*
+	 * Flush the icache in case there was previously some code
+	 * fetched from this address, perhaps a previous sigtramp.
+	 *
+	 * We don't need to flush the dcache, it's write through and
+	 * we just wrote the sigtramp code through it.
+	 */
+#ifdef CONFIG_SMP
+	metag_out32(1, SYSC_ICACHE_FLUSH);
+#else
+	metag_code_cache_flush((void *) addr, size);
+#endif
+}
+
+#ifdef CONFIG_METAG_L2C
+
+/*
+ * Perform a single specific CACHEWD operation on an address, masking lower bits
+ * of address first.
+ */
+static inline void cachewd_line(void *addr, unsigned int data)
+{
+	unsigned long masked = (unsigned long)addr & -0x40;
+	__builtin_meta2_cachewd((void *)masked, data);
+}
+
+/* Perform a certain CACHEW op on each cache line in a range */
+static inline void cachew_region_op(void *start, unsigned long size,
+				    unsigned int op)
+{
+	unsigned long offset = (unsigned long)start & 0x3f;
+	int i;
+	if (offset) {
+		size += offset;
+		start -= offset;
+	}
+	i = (size - 1) >> 6;
+	do {
+		__builtin_meta2_cachewd(start, op);
+		start += 0x40;
+	} while (i--);
+}
+
+/* prevent write fence and flushbacks being reordered in L2 */
+static inline void l2c_fence_flush(void *addr)
+{
+	/*
+	 * Synchronise by reading back and re-flushing.
+	 * It is assumed this access will miss, as the caller should have just
+	 * flushed the cache line.
+	 */
+	(void)(volatile u8 *)addr;
+	cachewd_line(addr, CACHEW_FLUSH_L1D_L2);
+}
+
+/* prevent write fence and writebacks being reordered in L2 */
+static inline void l2c_fence(void *addr)
+{
+	/*
+	 * A write back has occurred, but not necessarily an invalidate, so the
+	 * readback in l2c_fence_flush() would hit in the cache and have no
+	 * effect. Therefore fully flush the line first.
+	 */
+	cachewd_line(addr, CACHEW_FLUSH_L1D_L2);
+	l2c_fence_flush(addr);
+}
+
+/* Used to keep memory consistent when doing DMA. */
+static inline void flush_dcache_region(void *start, unsigned long size)
+{
+	/* metag_data_cache_flush won't flush L2 cache lines if size >= 4096 */
+	if (meta_l2c_is_enabled()) {
+		cachew_region_op(start, size, CACHEW_FLUSH_L1D_L2);
+		if (meta_l2c_is_writeback())
+			l2c_fence_flush(start + size - 1);
+	} else {
+		metag_data_cache_flush(start, size);
+	}
+}
+
+/* Write back dirty lines to memory (or do nothing if no writeback caches) */
+static inline void writeback_dcache_region(void *start, unsigned long size)
+{
+	if (meta_l2c_is_enabled() && meta_l2c_is_writeback()) {
+		cachew_region_op(start, size, CACHEW_WRITEBACK_L1D_L2);
+		l2c_fence(start + size - 1);
+	}
+}
+
+/* Invalidate (may also write back if necessary) */
+static inline void invalidate_dcache_region(void *start, unsigned long size)
+{
+	if (meta_l2c_is_enabled())
+		cachew_region_op(start, size, CACHEW_INVALIDATE_L1D_L2);
+	else
+		metag_data_cache_flush(start, size);
+}
+#else
+#define flush_dcache_region(s, l)	metag_data_cache_flush((s), (l))
+#define writeback_dcache_region(s, l)	do {} while (0)
+#define invalidate_dcache_region(s, l)	flush_dcache_region((s), (l))
+#endif
+
+static inline void copy_to_user_page(struct vm_area_struct *vma,
+				     struct page *page, unsigned long vaddr,
+				     void *dst, const void *src,
+				     unsigned long len)
+{
+	memcpy(dst, src, len);
+	flush_icache_range((unsigned long)dst, (unsigned long)dst + len);
+}
+
+static inline void copy_from_user_page(struct vm_area_struct *vma,
+				       struct page *page, unsigned long vaddr,
+				       void *dst, const void *src,
+				       unsigned long len)
+{
+	memcpy(dst, src, len);
+}
+
+#endif /* _METAG_CACHEFLUSH_H */