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Subject[PATCH v3 5/6] RISC-V: Implement compile-time fixed mappings
Date
This patch implements compile-time virtual to physical mappings. These
compile-time fixed mappings can be used by earlycon, ACPI, and early
ioremap for creating fixed mappings when FIX_EARLYCON_MEM=y.

To start with, we have enabled compile-time fixed mappings for earlycon.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
arch/riscv/Kconfig | 3 +++
arch/riscv/include/asm/fixmap.h | 44 +++++++++++++++++++++++++++++++++
arch/riscv/mm/init.c | 34 +++++++++++++++++++++++++
3 files changed, 81 insertions(+)
create mode 100644 arch/riscv/include/asm/fixmap.h

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 515fc3cc9687..3cfd10d35a28 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -89,6 +89,9 @@ config GENERIC_CSUM
config GENERIC_HWEIGHT
def_bool y

+config FIX_EARLYCON_MEM
+ def_bool y
+
config PGTABLE_LEVELS
int
default 3 if 64BIT
diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
new file mode 100644
index 000000000000..57afe604b495
--- /dev/null
+++ b/arch/riscv/include/asm/fixmap.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ */
+
+#ifndef _ASM_RISCV_FIXMAP_H
+#define _ASM_RISCV_FIXMAP_H
+
+#include <linux/kernel.h>
+#include <linux/sizes.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+
+/*
+ * Here we define all the compile-time 'special' virtual addresses.
+ * The point is to have a constant address at compile time, but to
+ * set the physical address only in the boot process.
+ *
+ * These 'compile-time allocated' memory buffers are page-sized. Use
+ * set_fixmap(idx,phys) to associate physical memory with fixmap indices.
+ */
+enum fixed_addresses {
+ FIX_HOLE,
+ FIX_EARLYCON_MEM_BASE,
+ __end_of_fixed_addresses
+};
+
+#define FIXADDR_SIZE (__end_of_fixed_addresses * PAGE_SIZE)
+#define FIXADDR_TOP (PAGE_OFFSET)
+#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
+
+#define FIXMAP_PAGE_IO PAGE_KERNEL
+
+#define __early_set_fixmap __set_fixmap
+
+#define __late_set_fixmap __set_fixmap
+#define __late_clear_fixmap(idx) __set_fixmap((idx), 0, FIXMAP_PAGE_CLEAR)
+
+extern void __set_fixmap(enum fixed_addresses idx,
+ phys_addr_t phys, pgprot_t prot);
+
+#include <asm-generic/fixmap.h>
+
+#endif /* _ASM_RISCV_FIXMAP_H */
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 7ed6ae90cf6b..efcbdb9b3da3 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -18,6 +18,7 @@
#include <linux/sizes.h>
#include <linux/of_fdt.h>

+#include <asm/fixmap.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/pgtable.h>
@@ -111,8 +112,28 @@ pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
#define NUM_SWAPPER_PMDS ((uintptr_t)-PAGE_OFFSET >> PGDIR_SHIFT)
pmd_t swapper_pmd[PTRS_PER_PMD*((-PAGE_OFFSET)/PGDIR_SIZE)] __page_aligned_bss;
pmd_t trampoline_pmd[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
#endif

+pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
+
+void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
+{
+ unsigned long addr = __fix_to_virt(idx);
+ pte_t *ptep;
+
+ BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
+
+ ptep = &fixmap_pte[pte_index(addr)];
+
+ if (pgprot_val(prot)) {
+ set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot));
+ } else {
+ pte_clear(&init_mm, addr, ptep);
+ local_flush_tlb_page(addr);
+ }
+}
+
asmlinkage void __init setup_vm(void)
{
extern char _start;
@@ -135,20 +156,33 @@ asmlinkage void __init setup_vm(void)

for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
+
swapper_pg_dir[o] =
pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i,
__pgprot(_PAGE_TABLE));
}
for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++)
swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot);
+
+ swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+ pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pmd),
+ __pgprot(_PAGE_TABLE));
+ fixmap_pmd[(FIXADDR_START >> PMD_SHIFT) % PTRS_PER_PMD] =
+ pfn_pmd(PFN_DOWN((uintptr_t)fixmap_pte),
+ __pgprot(_PAGE_TABLE));
#else
trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
pfn_pgd(PFN_DOWN(pa), prot);

for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
+
swapper_pg_dir[o] =
pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot);
}
+
+ swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+ pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pte),
+ __pgprot(_PAGE_TABLE));
#endif
}
--
2.17.1
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