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>

2 files changed, 170 insertions, 0 deletions

diff --git a/arch/csky/mm/Makefile b/arch/csky/mm/Makefile
index c94ef6481098..2c51918eb4fc 100644
--- a/arch/csky/mm/Makefile
+++ b/arch/csky/mm/Makefile
@@ -14,3 +14,4 @@ obj-y +=			syscache.o
 obj-y +=			tlb.o
 obj-y +=			asid.o
 obj-y +=			context.o
+obj-$(CONFIG_HAVE_TCM) +=	tcm.o
diff --git a/arch/csky/mm/tcm.c b/arch/csky/mm/tcm.c
new file mode 100644
index 000000000000..ddeb36328819
--- /dev/null
+++ b/arch/csky/mm/tcm.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/highmem.h>
+#include <linux/genalloc.h>
+#include <asm/tlbflush.h>
+#include <asm/fixmap.h>
+
+#if (CONFIG_ITCM_RAM_BASE == 0xffffffff)
+#error "You should define ITCM_RAM_BASE"
+#endif
+
+#ifdef CONFIG_HAVE_DTCM
+#if (CONFIG_DTCM_RAM_BASE == 0xffffffff)
+#error "You should define DTCM_RAM_BASE"
+#endif
+
+#if (CONFIG_DTCM_RAM_BASE == CONFIG_ITCM_RAM_BASE)
+#error "You should define correct DTCM_RAM_BASE"
+#endif
+#endif
+
+extern char __tcm_start, __tcm_end, __dtcm_start;
+
+static struct gen_pool *tcm_pool;
+
+static void __init tcm_mapping_init(void)
+{
+	pte_t *tcm_pte;
+	unsigned long vaddr, paddr;
+	int i;
+
+	paddr = CONFIG_ITCM_RAM_BASE;
+
+	if (pfn_valid(PFN_DOWN(CONFIG_ITCM_RAM_BASE)))
+		goto panic;
+
+#ifndef CONFIG_HAVE_DTCM
+	for (i = 0; i < TCM_NR_PAGES; i++) {
+#else
+	for (i = 0; i < CONFIG_ITCM_NR_PAGES; i++) {
+#endif
+		vaddr = __fix_to_virt(FIX_TCM - i);
+
+		tcm_pte =
+			pte_offset_kernel((pmd_t *)pgd_offset_k(vaddr), vaddr);
+
+		set_pte(tcm_pte, pfn_pte(__phys_to_pfn(paddr), PAGE_KERNEL));
+
+		flush_tlb_one(vaddr);
+
+		paddr = paddr + PAGE_SIZE;
+	}
+
+#ifdef CONFIG_HAVE_DTCM
+	if (pfn_valid(PFN_DOWN(CONFIG_DTCM_RAM_BASE)))
+		goto panic;
+
+	paddr = CONFIG_DTCM_RAM_BASE;
+
+	for (i = 0; i < CONFIG_DTCM_NR_PAGES; i++) {
+		vaddr = __fix_to_virt(FIX_TCM - CONFIG_ITCM_NR_PAGES - i);
+
+		tcm_pte =
+			pte_offset_kernel((pmd_t *) pgd_offset_k(vaddr), vaddr);
+
+		set_pte(tcm_pte, pfn_pte(__phys_to_pfn(paddr), PAGE_KERNEL));
+
+		flush_tlb_one(vaddr);
+
+		paddr = paddr + PAGE_SIZE;
+	}
+#endif
+
+#ifndef CONFIG_HAVE_DTCM
+	memcpy((void *)__fix_to_virt(FIX_TCM),
+				&__tcm_start, &__tcm_end - &__tcm_start);
+
+	pr_info("%s: mapping tcm va:0x%08lx to pa:0x%08x\n",
+			__func__, __fix_to_virt(FIX_TCM), CONFIG_ITCM_RAM_BASE);
+
+	pr_info("%s: __tcm_start va:0x%08lx size:%d\n",
+			__func__, (unsigned long)&__tcm_start, &__tcm_end - &__tcm_start);
+#else
+	memcpy((void *)__fix_to_virt(FIX_TCM),
+				&__tcm_start, &__dtcm_start - &__tcm_start);
+
+	pr_info("%s: mapping itcm va:0x%08lx to pa:0x%08x\n",
+			__func__, __fix_to_virt(FIX_TCM), CONFIG_ITCM_RAM_BASE);
+
+	pr_info("%s: __itcm_start va:0x%08lx size:%d\n",
+			__func__, (unsigned long)&__tcm_start, &__dtcm_start - &__tcm_start);
+
+	memcpy((void *)__fix_to_virt(FIX_TCM - CONFIG_ITCM_NR_PAGES),
+				&__dtcm_start, &__tcm_end - &__dtcm_start);
+
+	pr_info("%s: mapping dtcm va:0x%08lx to pa:0x%08x\n",
+			__func__, __fix_to_virt(FIX_TCM - CONFIG_ITCM_NR_PAGES),
+						CONFIG_DTCM_RAM_BASE);
+
+	pr_info("%s: __dtcm_start va:0x%08lx size:%d\n",
+			__func__, (unsigned long)&__dtcm_start, &__tcm_end - &__dtcm_start);
+
+#endif
+	return;
+panic:
+	panic("TCM init error");
+}
+
+void *tcm_alloc(size_t len)
+{
+	unsigned long vaddr;
+
+	if (!tcm_pool)
+		return NULL;
+
+	vaddr = gen_pool_alloc(tcm_pool, len);
+	if (!vaddr)
+		return NULL;
+
+	return (void *) vaddr;
+}
+EXPORT_SYMBOL(tcm_alloc);
+
+void tcm_free(void *addr, size_t len)
+{
+	gen_pool_free(tcm_pool, (unsigned long) addr, len);
+}
+EXPORT_SYMBOL(tcm_free);
+
+static int __init tcm_setup_pool(void)
+{
+#ifndef CONFIG_HAVE_DTCM
+	u32 pool_size = (u32) (TCM_NR_PAGES * PAGE_SIZE)
+				- (u32) (&__tcm_end - &__tcm_start);
+
+	u32 tcm_pool_start = __fix_to_virt(FIX_TCM)
+				+ (u32) (&__tcm_end - &__tcm_start);
+#else
+	u32 pool_size = (u32) (CONFIG_DTCM_NR_PAGES * PAGE_SIZE)
+				- (u32) (&__tcm_end - &__dtcm_start);
+
+	u32 tcm_pool_start = __fix_to_virt(FIX_TCM - CONFIG_ITCM_NR_PAGES)
+				+ (u32) (&__tcm_end - &__dtcm_start);
+#endif
+	int ret;
+
+	tcm_pool = gen_pool_create(2, -1);
+
+	ret = gen_pool_add(tcm_pool, tcm_pool_start, pool_size, -1);
+	if (ret) {
+		pr_err("%s: gen_pool add failed!\n", __func__);
+		return ret;
+	}
+
+	pr_info("%s: Added %d bytes @ 0x%08x to memory pool\n",
+		__func__, pool_size, tcm_pool_start);
+
+	return 0;
+}
+
+static int __init tcm_init(void)
+{
+	tcm_mapping_init();
+
+	tcm_setup_pool();
+
+	return 0;
+}
+arch_initcall(tcm_init);