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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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treea94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/xtensa/mmu.rst
parentInitial commit. (diff)
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Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+=============================
+MMUv3 initialization sequence
+=============================
+
+The code in the initialize_mmu macro sets up MMUv3 memory mapping
+identically to MMUv2 fixed memory mapping. Depending on
+CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX symbol this code is
+located in addresses it was linked for (symbol undefined), or not
+(symbol defined), so it needs to be position-independent.
+
+The code has the following assumptions:
+
+ - This code fragment is run only on an MMU v3.
+ - TLBs are in their reset state.
+ - ITLBCFG and DTLBCFG are zero (reset state).
+ - RASID is 0x04030201 (reset state).
+ - PS.RING is zero (reset state).
+ - LITBASE is zero (reset state, PC-relative literals); required to be PIC.
+
+TLB setup proceeds along the following steps.
+
+ Legend:
+
+ - VA = virtual address (two upper nibbles of it);
+ - PA = physical address (two upper nibbles of it);
+ - pc = physical range that contains this code;
+
+After step 2, we jump to virtual address in the range 0x40000000..0x5fffffff
+or 0x00000000..0x1fffffff, depending on whether the kernel was loaded below
+0x40000000 or above. That address corresponds to next instruction to execute
+in this code. After step 4, we jump to intended (linked) address of this code.
+The scheme below assumes that the kernel is loaded below 0x40000000.
+
+ ====== ===== ===== ===== ===== ====== ===== =====
+ - Step0 Step1 Step2 Step3 Step4 Step5
+
+ VA PA PA PA PA VA PA PA
+ ====== ===== ===== ===== ===== ====== ===== =====
+ E0..FF -> E0 -> E0 -> E0 F0..FF -> F0 -> F0
+ C0..DF -> C0 -> C0 -> C0 E0..EF -> F0 -> F0
+ A0..BF -> A0 -> A0 -> A0 D8..DF -> 00 -> 00
+ 80..9F -> 80 -> 80 -> 80 D0..D7 -> 00 -> 00
+ 60..7F -> 60 -> 60 -> 60
+ 40..5F -> 40 -> pc -> pc 40..5F -> pc
+ 20..3F -> 20 -> 20 -> 20
+ 00..1F -> 00 -> 00 -> 00
+ ====== ===== ===== ===== ===== ====== ===== =====
+
+The default location of IO peripherals is above 0xf0000000. This may be changed
+using a "ranges" property in a device tree simple-bus node. See the Devicetree
+Specification, section 4.5 for details on the syntax and semantics of
+simple-bus nodes. The following limitations apply:
+
+1. Only top level simple-bus nodes are considered
+
+2. Only one (first) simple-bus node is considered
+
+3. Empty "ranges" properties are not supported
+
+4. Only the first triplet in the "ranges" property is considered
+
+5. The parent-bus-address value is rounded down to the nearest 256MB boundary
+
+6. The IO area covers the entire 256MB segment of parent-bus-address; the
+ "ranges" triplet length field is ignored
+
+
+MMUv3 address space layouts.
+============================
+
+Default MMUv2-compatible layout::
+
+ Symbol VADDR Size
+ +------------------+
+ | Userspace | 0x00000000 TASK_SIZE
+ +------------------+ 0x40000000
+ +------------------+
+ | Page table | XCHAL_PAGE_TABLE_VADDR 0x80000000 XCHAL_PAGE_TABLE_SIZE
+ +------------------+
+ | KASAN shadow map | KASAN_SHADOW_START 0x80400000 KASAN_SHADOW_SIZE
+ +------------------+ 0x8e400000
+ +------------------+
+ | VMALLOC area | VMALLOC_START 0xc0000000 128MB - 64KB
+ +------------------+ VMALLOC_END
+ +------------------+
+ | Cache aliasing | TLBTEMP_BASE_1 0xc8000000 DCACHE_WAY_SIZE
+ | remap area 1 |
+ +------------------+
+ | Cache aliasing | TLBTEMP_BASE_2 DCACHE_WAY_SIZE
+ | remap area 2 |
+ +------------------+
+ +------------------+
+ | KMAP area | PKMAP_BASE PTRS_PER_PTE *
+ | | DCACHE_N_COLORS *
+ | | PAGE_SIZE
+ | | (4MB * DCACHE_N_COLORS)
+ +------------------+
+ | Atomic KMAP area | FIXADDR_START KM_TYPE_NR *
+ | | NR_CPUS *
+ | | DCACHE_N_COLORS *
+ | | PAGE_SIZE
+ +------------------+ FIXADDR_TOP 0xcffff000
+ +------------------+
+ | Cached KSEG | XCHAL_KSEG_CACHED_VADDR 0xd0000000 128MB
+ +------------------+
+ | Uncached KSEG | XCHAL_KSEG_BYPASS_VADDR 0xd8000000 128MB
+ +------------------+
+ | Cached KIO | XCHAL_KIO_CACHED_VADDR 0xe0000000 256MB
+ +------------------+
+ | Uncached KIO | XCHAL_KIO_BYPASS_VADDR 0xf0000000 256MB
+ +------------------+
+
+
+256MB cached + 256MB uncached layout::
+
+ Symbol VADDR Size
+ +------------------+
+ | Userspace | 0x00000000 TASK_SIZE
+ +------------------+ 0x40000000
+ +------------------+
+ | Page table | XCHAL_PAGE_TABLE_VADDR 0x80000000 XCHAL_PAGE_TABLE_SIZE
+ +------------------+
+ | KASAN shadow map | KASAN_SHADOW_START 0x80400000 KASAN_SHADOW_SIZE
+ +------------------+ 0x8e400000
+ +------------------+
+ | VMALLOC area | VMALLOC_START 0xa0000000 128MB - 64KB
+ +------------------+ VMALLOC_END
+ +------------------+
+ | Cache aliasing | TLBTEMP_BASE_1 0xa8000000 DCACHE_WAY_SIZE
+ | remap area 1 |
+ +------------------+
+ | Cache aliasing | TLBTEMP_BASE_2 DCACHE_WAY_SIZE
+ | remap area 2 |
+ +------------------+
+ +------------------+
+ | KMAP area | PKMAP_BASE PTRS_PER_PTE *
+ | | DCACHE_N_COLORS *
+ | | PAGE_SIZE
+ | | (4MB * DCACHE_N_COLORS)
+ +------------------+
+ | Atomic KMAP area | FIXADDR_START KM_TYPE_NR *
+ | | NR_CPUS *
+ | | DCACHE_N_COLORS *
+ | | PAGE_SIZE
+ +------------------+ FIXADDR_TOP 0xaffff000
+ +------------------+
+ | Cached KSEG | XCHAL_KSEG_CACHED_VADDR 0xb0000000 256MB
+ +------------------+
+ | Uncached KSEG | XCHAL_KSEG_BYPASS_VADDR 0xc0000000 256MB
+ +------------------+
+ +------------------+
+ | Cached KIO | XCHAL_KIO_CACHED_VADDR 0xe0000000 256MB
+ +------------------+
+ | Uncached KIO | XCHAL_KIO_BYPASS_VADDR 0xf0000000 256MB
+ +------------------+
+
+
+512MB cached + 512MB uncached layout::
+
+ Symbol VADDR Size
+ +------------------+
+ | Userspace | 0x00000000 TASK_SIZE
+ +------------------+ 0x40000000
+ +------------------+
+ | Page table | XCHAL_PAGE_TABLE_VADDR 0x80000000 XCHAL_PAGE_TABLE_SIZE
+ +------------------+
+ | KASAN shadow map | KASAN_SHADOW_START 0x80400000 KASAN_SHADOW_SIZE
+ +------------------+ 0x8e400000
+ +------------------+
+ | VMALLOC area | VMALLOC_START 0x90000000 128MB - 64KB
+ +------------------+ VMALLOC_END
+ +------------------+
+ | Cache aliasing | TLBTEMP_BASE_1 0x98000000 DCACHE_WAY_SIZE
+ | remap area 1 |
+ +------------------+
+ | Cache aliasing | TLBTEMP_BASE_2 DCACHE_WAY_SIZE
+ | remap area 2 |
+ +------------------+
+ +------------------+
+ | KMAP area | PKMAP_BASE PTRS_PER_PTE *
+ | | DCACHE_N_COLORS *
+ | | PAGE_SIZE
+ | | (4MB * DCACHE_N_COLORS)
+ +------------------+
+ | Atomic KMAP area | FIXADDR_START KM_TYPE_NR *
+ | | NR_CPUS *
+ | | DCACHE_N_COLORS *
+ | | PAGE_SIZE
+ +------------------+ FIXADDR_TOP 0x9ffff000
+ +------------------+
+ | Cached KSEG | XCHAL_KSEG_CACHED_VADDR 0xa0000000 512MB
+ +------------------+
+ | Uncached KSEG | XCHAL_KSEG_BYPASS_VADDR 0xc0000000 512MB
+ +------------------+
+ | Cached KIO | XCHAL_KIO_CACHED_VADDR 0xe0000000 256MB
+ +------------------+
+ | Uncached KIO | XCHAL_KIO_BYPASS_VADDR 0xf0000000 256MB
+ +------------------+