LoongArch: Add writecombine support for DMW-based ioremap()

Currently, only TLB-based ioremap() support writecombine, so add the
counterpart for DMW-based ioremap() with help of DMW2. The base address
(WRITECOMBINE_BASE) is configured as 0xa000000000000000.

DMW3 is unused by kernel now, however firmware may leave garbage in them
and interfere kernel's address mapping. So clear it as necessary.

BTW, centralize the DMW configuration to macro SETUP_DMWINS.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/addrspace.h

@@ -37,6 +37,10 @@ extern unsigned long vm_map_base;
 #define UNCACHE_BASE		CSR_DMW0_BASE
 #endif
 
+#ifndef WRITECOMBINE_BASE
+#define WRITECOMBINE_BASE	CSR_DMW2_BASE
+#endif
+
 #define DMW_PABITS	48
 #define TO_PHYS_MASK	((1ULL << DMW_PABITS) - 1)
 

arch/loongarch/include/asm/io.h

@@ -25,10 +25,16 @@ extern void __init early_iounmap(void __iomem *addr, unsigned long size);
 static inline void __iomem *ioremap_prot(phys_addr_t offset, unsigned long size,
 					 unsigned long prot_val)
 {
-	if (prot_val & _CACHE_CC)
+	switch (prot_val & _CACHE_MASK) {
+	case _CACHE_CC:
 		return (void __iomem *)(unsigned long)(CACHE_BASE + offset);
-	else
+	case _CACHE_SUC:
 		return (void __iomem *)(unsigned long)(UNCACHE_BASE + offset);
+	case _CACHE_WUC:
+		return (void __iomem *)(unsigned long)(WRITECOMBINE_BASE + offset);
+	default:
+		return NULL;
+	}
 }
 
 #define ioremap(offset, size)		\

arch/loongarch/include/asm/loongarch.h

@@ -877,7 +877,7 @@
 #define LOONGARCH_CSR_DMWIN2		0x182	/* 64 direct map win2: MEM */
 #define LOONGARCH_CSR_DMWIN3		0x183	/* 64 direct map win3: MEM */
 
-/* Direct Map window 0/1 */
+/* Direct Map window 0/1/2/3 */
 #define CSR_DMW0_PLV0		_CONST64_(1 << 0)
 #define CSR_DMW0_VSEG		_CONST64_(0x8000)
 #define CSR_DMW0_BASE		(CSR_DMW0_VSEG << DMW_PABITS)
@@ -889,6 +889,14 @@
 #define CSR_DMW1_BASE		(CSR_DMW1_VSEG << DMW_PABITS)
 #define CSR_DMW1_INIT		(CSR_DMW1_BASE | CSR_DMW1_MAT | CSR_DMW1_PLV0)
 
+#define CSR_DMW2_PLV0		_CONST64_(1 << 0)
+#define CSR_DMW2_MAT		_CONST64_(2 << 4)
+#define CSR_DMW2_VSEG		_CONST64_(0xa000)
+#define CSR_DMW2_BASE		(CSR_DMW2_VSEG << DMW_PABITS)
+#define CSR_DMW2_INIT		(CSR_DMW2_BASE | CSR_DMW2_MAT | CSR_DMW2_PLV0)
+
+#define CSR_DMW3_INIT		0x0
+
 /* Performance Counter registers */
 #define LOONGARCH_CSR_PERFCTRL0		0x200	/* 32 perf event 0 config */
 #define LOONGARCH_CSR_PERFCNTR0		0x201	/* 64 perf event 0 count value */

arch/loongarch/include/asm/stackframe.h

@@ -38,6 +38,17 @@
 	cfi_restore \reg \offset \docfi
 	.endm
 
+	.macro SETUP_DMWINS temp
+	li.d	\temp, CSR_DMW0_INIT	# WUC, PLV0, 0x8000 xxxx xxxx xxxx
+	csrwr	\temp, LOONGARCH_CSR_DMWIN0
+	li.d	\temp, CSR_DMW1_INIT	# CAC, PLV0, 0x9000 xxxx xxxx xxxx
+	csrwr	\temp, LOONGARCH_CSR_DMWIN1
+	li.d	\temp, CSR_DMW2_INIT	# WUC, PLV0, 0xa000 xxxx xxxx xxxx
+	csrwr	\temp, LOONGARCH_CSR_DMWIN2
+	li.d	\temp, CSR_DMW3_INIT	# 0x0, unused
+	csrwr	\temp, LOONGARCH_CSR_DMWIN3
+	.endm
+
 /* Jump to the runtime virtual address. */
 	.macro JUMP_VIRT_ADDR temp1 temp2
 	li.d	\temp1, CACHE_BASE

arch/loongarch/kernel/head.S

@@ -44,11 +44,7 @@ SYM_DATA(kernel_fsize, .long _kernel_fsize);
 SYM_CODE_START(kernel_entry)			# kernel entry point
 
 	/* Config direct window and set PG */
-	li.d		t0, CSR_DMW0_INIT	# UC, PLV0, 0x8000 xxxx xxxx xxxx
-	csrwr		t0, LOONGARCH_CSR_DMWIN0
-	li.d		t0, CSR_DMW1_INIT	# CA, PLV0, 0x9000 xxxx xxxx xxxx
-	csrwr		t0, LOONGARCH_CSR_DMWIN1
-
+	SETUP_DMWINS	t0
 	JUMP_VIRT_ADDR	t0, t1
 
 	/* Enable PG */
@@ -124,11 +120,8 @@ SYM_CODE_END(kernel_entry)
  * function after setting up the stack and tp registers.
  */
 SYM_CODE_START(smpboot_entry)
-	li.d		t0, CSR_DMW0_INIT	# UC, PLV0
-	csrwr		t0, LOONGARCH_CSR_DMWIN0
-	li.d		t0, CSR_DMW1_INIT	# CA, PLV0
-	csrwr		t0, LOONGARCH_CSR_DMWIN1
 
+	SETUP_DMWINS	t0
 	JUMP_VIRT_ADDR	t0, t1
 
 #ifdef CONFIG_PAGE_SIZE_4KB

arch/loongarch/power/suspend_asm.S

@@ -73,11 +73,7 @@ SYM_FUNC_START(loongarch_suspend_enter)
 	 * Reload all of the registers and return.
 	 */
 SYM_INNER_LABEL(loongarch_wakeup_start, SYM_L_GLOBAL)
-	li.d		t0, CSR_DMW0_INIT	# UC, PLV0
-	csrwr		t0, LOONGARCH_CSR_DMWIN0
-	li.d		t0, CSR_DMW1_INIT	# CA, PLV0
-	csrwr		t0, LOONGARCH_CSR_DMWIN1
-
+	SETUP_DMWINS	t0
 	JUMP_VIRT_ADDR	t0, t1
 
 	/* Enable PG */

drivers/firmware/efi/libstub/loongarch.c

@@ -74,6 +74,8 @@ efi_status_t efi_boot_kernel(void *handle, efi_loaded_image_t *image,
 	/* Config Direct Mapping */
 	csr_write64(CSR_DMW0_INIT, LOONGARCH_CSR_DMWIN0);
 	csr_write64(CSR_DMW1_INIT, LOONGARCH_CSR_DMWIN1);
+	csr_write64(CSR_DMW2_INIT, LOONGARCH_CSR_DMWIN2);
+	csr_write64(CSR_DMW3_INIT, LOONGARCH_CSR_DMWIN3);
 
 	real_kernel_entry = (void *)kernel_entry_address(kernel_addr, image);