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Diffstat (limited to 'Documentation/xtensa')
| -rw-r--r-- | Documentation/xtensa/atomctl.rst | 51 | ||||
| -rw-r--r-- | Documentation/xtensa/booting.rst | 22 | ||||
| -rw-r--r-- | Documentation/xtensa/features.rst | 3 | ||||
| -rw-r--r-- | Documentation/xtensa/index.rst | 14 | ||||
| -rw-r--r-- | Documentation/xtensa/mmu.rst | 198 |
5 files changed, 288 insertions, 0 deletions
diff --git a/Documentation/xtensa/atomctl.rst b/Documentation/xtensa/atomctl.rst new file mode 100644 index 000000000..1ecbd0ba9 --- /dev/null +++ b/Documentation/xtensa/atomctl.rst @@ -0,0 +1,51 @@ +=========================================== +Atomic Operation Control (ATOMCTL) Register +=========================================== + +We Have Atomic Operation Control (ATOMCTL) Register. +This register determines the effect of using a S32C1I instruction +with various combinations of: + + 1. With and without an Coherent Cache Controller which + can do Atomic Transactions to the memory internally. + + 2. With and without An Intelligent Memory Controller which + can do Atomic Transactions itself. + +The Core comes up with a default value of for the three types of cache ops:: + + 0x28: (WB: Internal, WT: Internal, BY:Exception) + +On the FPGA Cards we typically simulate an Intelligent Memory controller +which can implement RCW transactions. For FPGA cards with an External +Memory controller we let it to the atomic operations internally while +doing a Cached (WB) transaction and use the Memory RCW for un-cached +operations. + +For systems without an coherent cache controller, non-MX, we always +use the memory controllers RCW, thought non-MX controlers likely +support the Internal Operation. + +CUSTOMER-WARNING: + Virtually all customers buy their memory controllers from vendors that + don't support atomic RCW memory transactions and will likely want to + configure this register to not use RCW. + +Developers might find using RCW in Bypass mode convenient when testing +with the cache being bypassed; for example studying cache alias problems. + +See Section 4.3.12.4 of ISA; Bits:: + + WB WT BY + 5 4 | 3 2 | 1 0 + +========= ================== ================== =============== + 2 Bit + Field + Values WB - Write Back WT - Write Thru BY - Bypass +========= ================== ================== =============== + 0 Exception Exception Exception + 1 RCW Transaction RCW Transaction RCW Transaction + 2 Internal Operation Internal Operation Reserved + 3 Reserved Reserved Reserved +========= ================== ================== =============== diff --git a/Documentation/xtensa/booting.rst b/Documentation/xtensa/booting.rst new file mode 100644 index 000000000..e1b83707e --- /dev/null +++ b/Documentation/xtensa/booting.rst @@ -0,0 +1,22 @@ +===================================== +Passing boot parameters to the kernel +===================================== + +Boot parameters are represented as a TLV list in the memory. Please see +arch/xtensa/include/asm/bootparam.h for definition of the bp_tag structure and +tag value constants. First entry in the list must have type BP_TAG_FIRST, last +entry must have type BP_TAG_LAST. The address of the first list entry is +passed to the kernel in the register a2. The address type depends on MMU type: + +- For configurations without MMU, with region protection or with MPU the + address must be the physical address. +- For configurations with region translarion MMU or with MMUv3 and CONFIG_MMU=n + the address must be a valid address in the current mapping. The kernel will + not change the mapping on its own. +- For configurations with MMUv2 the address must be a virtual address in the + default virtual mapping (0xd0000000..0xffffffff). +- For configurations with MMUv3 and CONFIG_MMU=y the address may be either a + virtual or physical address. In either case it must be within the default + virtual mapping. It is considered physical if it is within the range of + physical addresses covered by the default KSEG mapping (XCHAL_KSEG_PADDR.. + XCHAL_KSEG_PADDR + XCHAL_KSEG_SIZE), otherwise it is considered virtual. diff --git a/Documentation/xtensa/features.rst b/Documentation/xtensa/features.rst new file mode 100644 index 000000000..6b92c7bfa --- /dev/null +++ b/Documentation/xtensa/features.rst @@ -0,0 +1,3 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. kernel-feat:: $srctree/Documentation/features xtensa diff --git a/Documentation/xtensa/index.rst b/Documentation/xtensa/index.rst new file mode 100644 index 000000000..69952446a --- /dev/null +++ b/Documentation/xtensa/index.rst @@ -0,0 +1,14 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================== +Xtensa Architecture +=================== + +.. toctree:: + :maxdepth: 1 + + atomctl + booting + mmu + + features diff --git a/Documentation/xtensa/mmu.rst b/Documentation/xtensa/mmu.rst new file mode 100644 index 000000000..450573afa --- /dev/null +++ b/Documentation/xtensa/mmu.rst @@ -0,0 +1,198 @@ +============================= +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 + +------------------+ |