1b2441318SGreg Kroah-Hartman/* SPDX-License-Identifier: GPL-2.0 */ 21da177e4SLinus Torvalds/* 31da177e4SLinus Torvalds * arch/alpha/lib/ev6-clear_user.S 41da177e4SLinus Torvalds * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> 51da177e4SLinus Torvalds * 61da177e4SLinus Torvalds * Zero user space, handling exceptions as we go. 71da177e4SLinus Torvalds * 81da177e4SLinus Torvalds * We have to make sure that $0 is always up-to-date and contains the 91da177e4SLinus Torvalds * right "bytes left to zero" value (and that it is updated only _after_ 101da177e4SLinus Torvalds * a successful copy). There is also some rather minor exception setup 111da177e4SLinus Torvalds * stuff. 121da177e4SLinus Torvalds * 131da177e4SLinus Torvalds * Much of the information about 21264 scheduling/coding comes from: 141da177e4SLinus Torvalds * Compiler Writer's Guide for the Alpha 21264 151da177e4SLinus Torvalds * abbreviated as 'CWG' in other comments here 161da177e4SLinus Torvalds * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html 171da177e4SLinus Torvalds * Scheduling notation: 181da177e4SLinus Torvalds * E - either cluster 191da177e4SLinus Torvalds * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 201da177e4SLinus Torvalds * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 211da177e4SLinus Torvalds * Try not to change the actual algorithm if possible for consistency. 221da177e4SLinus Torvalds * Determining actual stalls (other than slotting) doesn't appear to be easy to do. 231da177e4SLinus Torvalds * From perusing the source code context where this routine is called, it is 241da177e4SLinus Torvalds * a fair assumption that significant fractions of entire pages are zeroed, so 251da177e4SLinus Torvalds * it's going to be worth the effort to hand-unroll a big loop, and use wh64. 261da177e4SLinus Torvalds * ASSUMPTION: 271da177e4SLinus Torvalds * The believed purpose of only updating $0 after a store is that a signal 281da177e4SLinus Torvalds * may come along during the execution of this chunk of code, and we don't 291da177e4SLinus Torvalds * want to leave a hole (and we also want to avoid repeating lots of work) 301da177e4SLinus Torvalds */ 311da177e4SLinus Torvalds 32*f3c78e94SMasahiro Yamada#include <linux/export.h> 331da177e4SLinus Torvalds/* Allow an exception for an insn; exit if we get one. */ 341da177e4SLinus Torvalds#define EX(x,y...) \ 351da177e4SLinus Torvalds 99: x,##y; \ 361da177e4SLinus Torvalds .section __ex_table,"a"; \ 371da177e4SLinus Torvalds .long 99b - .; \ 381da177e4SLinus Torvalds lda $31, $exception-99b($31); \ 391da177e4SLinus Torvalds .previous 401da177e4SLinus Torvalds 411da177e4SLinus Torvalds .set noat 421da177e4SLinus Torvalds .set noreorder 431da177e4SLinus Torvalds .align 4 441da177e4SLinus Torvalds 4585250231SAl Viro .globl __clear_user 4685250231SAl Viro .ent __clear_user 4785250231SAl Viro .frame $30, 0, $26 481da177e4SLinus Torvalds .prologue 0 491da177e4SLinus Torvalds 501da177e4SLinus Torvalds # Pipeline info : Slotting & Comments 5185250231SAl Viro__clear_user: 5285250231SAl Viro and $17, $17, $0 5385250231SAl Viro and $16, 7, $4 # .. E .. .. : find dest head misalignment 541da177e4SLinus Torvalds beq $0, $zerolength # U .. .. .. : U L U L 551da177e4SLinus Torvalds 561da177e4SLinus Torvalds addq $0, $4, $1 # .. .. .. E : bias counter 571da177e4SLinus Torvalds and $1, 7, $2 # .. .. E .. : number of misaligned bytes in tail 581da177e4SLinus Torvalds# Note - we never actually use $2, so this is a moot computation 591da177e4SLinus Torvalds# and we can rewrite this later... 601da177e4SLinus Torvalds srl $1, 3, $1 # .. E .. .. : number of quadwords to clear 611da177e4SLinus Torvalds beq $4, $headalign # U .. .. .. : U L U L 621da177e4SLinus Torvalds 631da177e4SLinus Torvalds/* 641da177e4SLinus Torvalds * Head is not aligned. Write (8 - $4) bytes to head of destination 6585250231SAl Viro * This means $16 is known to be misaligned 661da177e4SLinus Torvalds */ 6785250231SAl Viro EX( ldq_u $5, 0($16) ) # .. .. .. L : load dst word to mask back in 681da177e4SLinus Torvalds beq $1, $onebyte # .. .. U .. : sub-word store? 6985250231SAl Viro mskql $5, $16, $5 # .. U .. .. : take care of misaligned head 7085250231SAl Viro addq $16, 8, $16 # E .. .. .. : L U U L 711da177e4SLinus Torvalds 7285250231SAl Viro EX( stq_u $5, -8($16) ) # .. .. .. L : 731da177e4SLinus Torvalds subq $1, 1, $1 # .. .. E .. : 741da177e4SLinus Torvalds addq $0, $4, $0 # .. E .. .. : bytes left -= 8 - misalignment 751da177e4SLinus Torvalds subq $0, 8, $0 # E .. .. .. : U L U L 761da177e4SLinus Torvalds 771da177e4SLinus Torvalds .align 4 781da177e4SLinus Torvalds/* 791da177e4SLinus Torvalds * (The .align directive ought to be a moot point) 801da177e4SLinus Torvalds * values upon initial entry to the loop 811da177e4SLinus Torvalds * $1 is number of quadwords to clear (zero is a valid value) 821da177e4SLinus Torvalds * $2 is number of trailing bytes (0..7) ($2 never used...) 8385250231SAl Viro * $16 is known to be aligned 0mod8 841da177e4SLinus Torvalds */ 851da177e4SLinus Torvalds$headalign: 861da177e4SLinus Torvalds subq $1, 16, $4 # .. .. .. E : If < 16, we can not use the huge loop 8785250231SAl Viro and $16, 0x3f, $2 # .. .. E .. : Forward work for huge loop 881da177e4SLinus Torvalds subq $2, 0x40, $3 # .. E .. .. : bias counter (huge loop) 891da177e4SLinus Torvalds blt $4, $trailquad # U .. .. .. : U L U L 901da177e4SLinus Torvalds 911da177e4SLinus Torvalds/* 921da177e4SLinus Torvalds * We know that we're going to do at least 16 quads, which means we are 931da177e4SLinus Torvalds * going to be able to use the large block clear loop at least once. 941da177e4SLinus Torvalds * Figure out how many quads we need to clear before we are 0mod64 aligned 951da177e4SLinus Torvalds * so we can use the wh64 instruction. 961da177e4SLinus Torvalds */ 971da177e4SLinus Torvalds 981da177e4SLinus Torvalds nop # .. .. .. E 991da177e4SLinus Torvalds nop # .. .. E .. 1001da177e4SLinus Torvalds nop # .. E .. .. 1011da177e4SLinus Torvalds beq $3, $bigalign # U .. .. .. : U L U L : Aligned 0mod64 1021da177e4SLinus Torvalds 1031da177e4SLinus Torvalds$alignmod64: 10485250231SAl Viro EX( stq_u $31, 0($16) ) # .. .. .. L 1051da177e4SLinus Torvalds addq $3, 8, $3 # .. .. E .. 1061da177e4SLinus Torvalds subq $0, 8, $0 # .. E .. .. 1071da177e4SLinus Torvalds nop # E .. .. .. : U L U L 1081da177e4SLinus Torvalds 1091da177e4SLinus Torvalds nop # .. .. .. E 1101da177e4SLinus Torvalds subq $1, 1, $1 # .. .. E .. 11185250231SAl Viro addq $16, 8, $16 # .. E .. .. 1121da177e4SLinus Torvalds blt $3, $alignmod64 # U .. .. .. : U L U L 1131da177e4SLinus Torvalds 1141da177e4SLinus Torvalds$bigalign: 1151da177e4SLinus Torvalds/* 1161da177e4SLinus Torvalds * $0 is the number of bytes left 1171da177e4SLinus Torvalds * $1 is the number of quads left 11885250231SAl Viro * $16 is aligned 0mod64 1191da177e4SLinus Torvalds * we know that we'll be taking a minimum of one trip through 1201da177e4SLinus Torvalds * CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle 1211da177e4SLinus Torvalds * We are _not_ going to update $0 after every single store. That 1221da177e4SLinus Torvalds * would be silly, because there will be cross-cluster dependencies 1231da177e4SLinus Torvalds * no matter how the code is scheduled. By doing it in slightly 1241da177e4SLinus Torvalds * staggered fashion, we can still do this loop in 5 fetches 1251da177e4SLinus Torvalds * The worse case will be doing two extra quads in some future execution, 1261da177e4SLinus Torvalds * in the event of an interrupted clear. 1271da177e4SLinus Torvalds * Assumes the wh64 needs to be for 2 trips through the loop in the future 1281da177e4SLinus Torvalds * The wh64 is issued on for the starting destination address for trip +2 1291da177e4SLinus Torvalds * through the loop, and if there are less than two trips left, the target 1301da177e4SLinus Torvalds * address will be for the current trip. 1311da177e4SLinus Torvalds */ 1321da177e4SLinus Torvalds nop # E : 1331da177e4SLinus Torvalds nop # E : 1341da177e4SLinus Torvalds nop # E : 13585250231SAl Viro bis $16,$16,$3 # E : U L U L : Initial wh64 address is dest 1361da177e4SLinus Torvalds /* This might actually help for the current trip... */ 1371da177e4SLinus Torvalds 1381da177e4SLinus Torvalds$do_wh64: 1391da177e4SLinus Torvalds wh64 ($3) # .. .. .. L1 : memory subsystem hint 1401da177e4SLinus Torvalds subq $1, 16, $4 # .. .. E .. : Forward calculation - repeat the loop? 14185250231SAl Viro EX( stq_u $31, 0($16) ) # .. L .. .. 1421da177e4SLinus Torvalds subq $0, 8, $0 # E .. .. .. : U L U L 1431da177e4SLinus Torvalds 14485250231SAl Viro addq $16, 128, $3 # E : Target address of wh64 14585250231SAl Viro EX( stq_u $31, 8($16) ) # L : 14685250231SAl Viro EX( stq_u $31, 16($16) ) # L : 1471da177e4SLinus Torvalds subq $0, 16, $0 # E : U L L U 1481da177e4SLinus Torvalds 1491da177e4SLinus Torvalds nop # E : 15085250231SAl Viro EX( stq_u $31, 24($16) ) # L : 15185250231SAl Viro EX( stq_u $31, 32($16) ) # L : 1521da177e4SLinus Torvalds subq $0, 168, $5 # E : U L L U : two trips through the loop left? 1531da177e4SLinus Torvalds /* 168 = 192 - 24, since we've already completed some stores */ 1541da177e4SLinus Torvalds 1551da177e4SLinus Torvalds subq $0, 16, $0 # E : 15685250231SAl Viro EX( stq_u $31, 40($16) ) # L : 15785250231SAl Viro EX( stq_u $31, 48($16) ) # L : 15885250231SAl Viro cmovlt $5, $16, $3 # E : U L L U : Latency 2, extra mapping cycle 1591da177e4SLinus Torvalds 1601da177e4SLinus Torvalds subq $1, 8, $1 # E : 1611da177e4SLinus Torvalds subq $0, 16, $0 # E : 16285250231SAl Viro EX( stq_u $31, 56($16) ) # L : 1631da177e4SLinus Torvalds nop # E : U L U L 1641da177e4SLinus Torvalds 1651da177e4SLinus Torvalds nop # E : 1661da177e4SLinus Torvalds subq $0, 8, $0 # E : 16785250231SAl Viro addq $16, 64, $16 # E : 1681da177e4SLinus Torvalds bge $4, $do_wh64 # U : U L U L 1691da177e4SLinus Torvalds 1701da177e4SLinus Torvalds$trailquad: 1711da177e4SLinus Torvalds # zero to 16 quadwords left to store, plus any trailing bytes 1721da177e4SLinus Torvalds # $1 is the number of quadwords left to go. 1731da177e4SLinus Torvalds # 1741da177e4SLinus Torvalds nop # .. .. .. E 1751da177e4SLinus Torvalds nop # .. .. E .. 1761da177e4SLinus Torvalds nop # .. E .. .. 1771da177e4SLinus Torvalds beq $1, $trailbytes # U .. .. .. : U L U L : Only 0..7 bytes to go 1781da177e4SLinus Torvalds 1791da177e4SLinus Torvalds$onequad: 18085250231SAl Viro EX( stq_u $31, 0($16) ) # .. .. .. L 1811da177e4SLinus Torvalds subq $1, 1, $1 # .. .. E .. 1821da177e4SLinus Torvalds subq $0, 8, $0 # .. E .. .. 1831da177e4SLinus Torvalds nop # E .. .. .. : U L U L 1841da177e4SLinus Torvalds 1851da177e4SLinus Torvalds nop # .. .. .. E 1861da177e4SLinus Torvalds nop # .. .. E .. 18785250231SAl Viro addq $16, 8, $16 # .. E .. .. 1881da177e4SLinus Torvalds bgt $1, $onequad # U .. .. .. : U L U L 1891da177e4SLinus Torvalds 1901da177e4SLinus Torvalds # We have an unknown number of bytes left to go. 1911da177e4SLinus Torvalds$trailbytes: 1921da177e4SLinus Torvalds nop # .. .. .. E 1931da177e4SLinus Torvalds nop # .. .. E .. 1941da177e4SLinus Torvalds nop # .. E .. .. 1951da177e4SLinus Torvalds beq $0, $zerolength # U .. .. .. : U L U L 1961da177e4SLinus Torvalds 1971da177e4SLinus Torvalds # $0 contains the number of bytes left to copy (0..31) 1981da177e4SLinus Torvalds # so we will use $0 as the loop counter 1991da177e4SLinus Torvalds # We know for a fact that $0 > 0 zero due to previous context 2001da177e4SLinus Torvalds$onebyte: 20185250231SAl Viro EX( stb $31, 0($16) ) # .. .. .. L 2021da177e4SLinus Torvalds subq $0, 1, $0 # .. .. E .. : 20385250231SAl Viro addq $16, 1, $16 # .. E .. .. : 2041da177e4SLinus Torvalds bgt $0, $onebyte # U .. .. .. : U L U L 2051da177e4SLinus Torvalds 2061da177e4SLinus Torvalds$zerolength: 2071da177e4SLinus Torvalds$exception: # Destination for exception recovery(?) 2081da177e4SLinus Torvalds nop # .. .. .. E : 2091da177e4SLinus Torvalds nop # .. .. E .. : 2101da177e4SLinus Torvalds nop # .. E .. .. : 21185250231SAl Viro ret $31, ($26), 1 # L0 .. .. .. : L U L U 21285250231SAl Viro .end __clear_user 21385250231SAl Viro EXPORT_SYMBOL(__clear_user) 214