csky: Tightly-Coupled Memory or Sram support

The implementation are not only used by TCM but also used by sram on
SOC bus. It follow existed linux tcm software interface, so that old
tcm application codes could be re-used directly.

Software interface list in asm/tcm.h:
 - Variables/Const: 	__tcmdata, __tcmconst
 - Functions:		__tcmfunc, __tcmlocalfunc
 - Malloc/Free:		tcm_alloc, tcm_free

In linux menuconfig:
 - Choose a TCM contain instrctions + data or separated in ITCM/DTCM.
 - Determine TCM_BASE (DTCM_BASE) in phyiscal address.
 - Determine size of TCM or ITCM(DTCM) in page counts.

Here is hello tcm example from Documentation/arm/tcm.rst which could
be directly used:

/* Uninitialized data */
static u32 __tcmdata tcmvar;
/* Initialized data */
static u32 __tcmdata tcmassigned = 0x2BADBABEU;
/* Constant */
static const u32 __tcmconst tcmconst = 0xCAFEBABEU;

static void __tcmlocalfunc tcm_to_tcm(void)
{
	int i;
	for (i = 0; i < 100; i++)
		tcmvar ++;
}

static void __tcmfunc hello_tcm(void)
{
	/* Some abstract code that runs in ITCM */
	int i;
	for (i = 0; i < 100; i++) {
		tcmvar ++;
	}
	tcm_to_tcm();
}

static void __init test_tcm(void)
{
	u32 *tcmem;
	int i;

	hello_tcm();
	printk("Hello TCM executed from ITCM RAM\n");

	printk("TCM variable from testrun: %u @ %p\n", tcmvar, &tcmvar);
	tcmvar = 0xDEADBEEFU;
	printk("TCM variable: 0x%x @ %p\n", tcmvar, &tcmvar);

	printk("TCM assigned variable: 0x%x @ %p\n", tcmassigned, &tcmassigned);

	printk("TCM constant: 0x%x @ %p\n", tcmconst, &tcmconst);

	/* Allocate some TCM memory from the pool */
	tcmem = tcm_alloc(20);
	if (tcmem) {
		printk("TCM Allocated 20 bytes of TCM @ %p\n", tcmem);
		tcmem[0] = 0xDEADBEEFU;
		tcmem[1] = 0x2BADBABEU;
		tcmem[2] = 0xCAFEBABEU;
		tcmem[3] = 0xDEADBEEFU;
		tcmem[4] = 0x2BADBABEU;
		for (i = 0; i < 5; i++)
			printk("TCM tcmem[%d] = %08x\n", i, tcmem[i]);
		tcm_free(tcmem, 20);
	}
}

TODO:
 - Separate fixup mapping from highmem
 - Support abiv1

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

3 files changed, 50 insertions, 1 deletions

diff --git a/arch/csky/include/asm/fixmap.h b/arch/csky/include/asm/fixmap.h
index 380ff0a307df..4350578faa1c 100644
--- a/arch/csky/include/asm/fixmap.h
+++ b/arch/csky/include/asm/fixmap.h
@@ -5,12 +5,16 @@
 #define __ASM_CSKY_FIXMAP_H
 
 #include <asm/page.h>
+#include <asm/memory.h>
 #ifdef CONFIG_HIGHMEM
 #include <linux/threads.h>
 #include <asm/kmap_types.h>
 #endif
 
 enum fixed_addresses {
+#ifdef CONFIG_HAVE_TCM
+	FIX_TCM = TCM_NR_PAGES,
+#endif
 #ifdef CONFIG_HIGHMEM
 	FIX_KMAP_BEGIN,
 	FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
@@ -18,7 +22,6 @@ enum fixed_addresses {
 	__end_of_fixed_addresses
 };
 
-#define FIXADDR_TOP	0xffffc000
 #define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
 #define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)
 
diff --git a/arch/csky/include/asm/memory.h b/arch/csky/include/asm/memory.h
new file mode 100644
index 000000000000..cdffbd0a500b
--- /dev/null
+++ b/arch/csky/include/asm/memory.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_CSKY_MEMORY_H
+#define __ASM_CSKY_MEMORY_H
+
+#include <linux/compiler.h>
+#include <linux/const.h>
+#include <linux/types.h>
+#include <linux/sizes.h>
+
+#define FIXADDR_TOP	_AC(0xffffc000, UL)
+
+#ifdef CONFIG_HAVE_TCM
+#ifdef CONFIG_HAVE_DTCM
+#define TCM_NR_PAGES	(CONFIG_ITCM_NR_PAGES + CONFIG_DTCM_NR_PAGES)
+#else
+#define TCM_NR_PAGES	(CONFIG_ITCM_NR_PAGES)
+#endif
+#define FIXADDR_TCM	_AC(FIXADDR_TOP - (TCM_NR_PAGES * PAGE_SIZE), UL)
+#endif
+
+#endif
diff --git a/arch/csky/include/asm/tcm.h b/arch/csky/include/asm/tcm.h
new file mode 100644
index 000000000000..2b135cefb73f
--- /dev/null
+++ b/arch/csky/include/asm/tcm.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_CSKY_TCM_H
+#define __ASM_CSKY_TCM_H
+
+#ifndef CONFIG_HAVE_TCM
+#error "You should not be including tcm.h unless you have a TCM!"
+#endif
+
+#include <linux/compiler.h>
+
+/* Tag variables with this */
+#define __tcmdata __section(.tcm.data)
+/* Tag constants with this */
+#define __tcmconst __section(.tcm.rodata)
+/* Tag functions inside TCM called from outside TCM with this */
+#define __tcmfunc __section(.tcm.text) noinline
+/* Tag function inside TCM called from inside TCM  with this */
+#define __tcmlocalfunc __section(.tcm.text)
+
+void *tcm_alloc(size_t len);
+void tcm_free(void *addr, size_t len);
+
+#endif