Commit 32a7ede (MIPS: dsp: Add assembler support for DSP ASEs) has
enabled the use of DSP ASE specific instructions such as rddsp and wrdsp
under the idea that all code path that will make use of these two
instructions are properly checking for cpu_has_dsp to ensure that the
particular CPU we are running on *actually* supports DSP ASE.
This commit actually causes the following oops on QEMU Malta emulating a
MIPS 24Kc without the DSP ASE implemented:
[ 7.960000] Reserved instruction in kernel
[ 7.960000] Cpu 0
[ 7.960000] $ 0 : 00000000 00000000 00000014 00000005
[ 7.960000] $ 4 : 8fc2de48 00000001 00000000 8f59ddb0
[ 7.960000] $ 8 : 8f5ceec4 00000018 00000c00 00800000
[ 7.960000] $12 : 00000100 00000200 00000000 00457b84
[ 7.960000] $16 : 00000000 8fc2ba78 8f4ec980 00000001
[ 7.960000] $20 : 80418f90 00000000 00000000 000002dd
[ 7.960000] $24 : 0000009c 7730d7b8
[ 7.960000] $28 : 8f59c000 8f59dd38 00000001 80104248
[ 7.960000] Hi : 0000001d
[ 7.960000] Lo : 0000000b
[ 7.960000] epc : 801041ec thread_saved_pc+0x2c/0x38
[ 7.960000] Not tainted
[ 7.960000] ra : 80104248 get_wchan+0x48/0xac
[ 7.960000] Status: 1000b703 KERNEL EXL IE
[ 7.960000] Cause : 10800028
[ 7.960000] PrId : 00019300 (MIPS 24Kc)
[ 7.960000] Modules linked in:
[ 7.960000] Process killall (pid: 1574, threadinfo=8f59c000,
task=8fd14558, tls=773aa440)
[ 7.960000] Stack : 8fc2ba78 8012b008 0000000c 0000001d 00000000
00000000 8f58a380
8f58a380 8fc2ba78 80202668 8f59de78 8f468600 8f59de28
801b2a3c 8f59df00 8f98ba20 74696e69
8f468600 8f59de28 801b7308 0081c007 00000000 00000000
00000000 00000000 00000000 00000000
00000000 8fc2bbb4 00000001 0000001d 0000000b 77f038cc
7fe80648 ffffffff ffffffff 00000000
00000001 0016e000 00000000 ...
[ 7.960000] Call Trace:
[ 7.960000] [<801041ec>] thread_saved_pc+0x2c/0x38
[ 7.960000] [<80104248>] get_wchan+0x48/0xac
The disassembly of thread_saved_pc points to the following:
000006d0 <thread_saved_pc>:
6d0: 8c820208 lw v0,520(a0)
6d4: 3c030000 lui v1,0x0
6d8: 24630000 addiu v1,v1,0
6dc: 10430008 beq v0,v1,700 <thread_saved_pc+0x30>
6e0: 00000000 nop
6e4: 3c020000 lui v0,0x0
6e8: 8c43000c lw v1,12(v0)
6ec: 04620004 bltzl v1,700 <thread_saved_pc+0x30>
6f0: 00001021 move v0,zero
6f4: 8c840200 lw a0,512(a0)
6f8: 00031080 sll v0,v1,0x2
6fc: 7c44100a lwx v0,a0(v0) <------------
700: 03e00008 jr ra
704: 00000000 nop
If we specifically disable -mdsp/-mdspr2 for arch/mips/kernel/process.o,
we get the following (non-crashing) assembly:
00000708 <thread_saved_pc>:
708: 8c820208 lw v0,520(a0)
70c: 3c030000 lui v1,0x0
710: 24630000 addiu v1,v1,0
714: 10430009 beq v0,v1,73c <thread_saved_pc+0x34>
718: 00000000 nop
71c: 3c020000 lui v0,0x0
720: 8c42000c lw v0,12(v0)
724: 04420005 bltzl v0,73c <thread_saved_pc+0x34>
728: 00001021 move v0,zero
72c: 8c830200 lw v1,512(a0)
730: 00021080 sll v0,v0,0x2
734: 00431021 addu v0,v0,v1
738: 8c420000 lw v0,0(v0)
73c: 03e00008 jr ra
740: 00000000 nop
The specific line that leads a different assembly being produced is:
unsigned long thread_saved_pc(struct task_struct *tsk)
...
return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset]; <---
The problem here is that the compiler was given the right to use DSP
instructions with the -mdsp / -mdspr2 command-line switches and
performed some optimization for us and used DSP ASE instructions where
we are not checking that the running CPU actually supports DSP ASE.
This patch fixes the issue by partially reverting commit 32a7ede for
arch/mips/kernel/Makefile in order to remove the -mdsp / -mdspr2
compiler command-line switches such that we are now guaranteed that the
compiler will not optimize using DSP ASE reserved instructions. We also
need to fixup the rddsp/wrdsp and m{t,h}{hi,lo}{0,1,2,3} macros in
arch/mips/include/asm/mipsregs.h to tell the assembler that we are going
to explicitely use DSP ASE reserved instructions. The comment in
arch/mips/kernel/Makefile is also updated to reflect that.
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Acked-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: blogic@openwrt.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Add new clocksource that uses the counter present on the MIPS Global Interrupt Controller. Signed-off-by: Steven J. Hill <sjhill@mips.com> Patchwork: http://patchwork.linux-mips.org/patch/4681/ Signed-off-by: John Crispin <blogic@openwrt.org>
Newer toolchains support the DSP and DSP Rev2 instructions. This patch performs a check for that support and adds compiler and assembler flags for only the files that need use those instructions. Signed-off-by: Steven J. Hill <sjhill@mips.com> Acked-by: Florian Fainelli <florian@openwrt.org> Patchwork: http://patchwork.linux-mips.org/patch/4752/ Signed-off-by: John Crispin <blogic@openwrt.org>
Having received another series of whitespace patches I decided to do this once and for all rather than dealing with this kind of patches trickling in forever. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Nobody seems to be interested anymore and upstream also never had an ethernet driver. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Manuel Lauss <manuel.lauss@gmail.com> writes: I introduced it as a fallback because early revisions of Alchemy hardware we shipped had a non-functional 32kHz timer and had to rely on the r4k timer instead. Previously the r4k timer was initialized regardless, but it's useless with the "wait" instruction. So long story short: I need either the on-chip 32kHz timer OR the r4k timer if the 32kHz one is unusable, but not both, and r4k timer is useless when au1k_idle is in use. The current in-kernel Alchemy boards all work with the 32kHz timer, so I'm not against removing R4K_LIB symbols. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Manuel Lauss <manuel.lauss@gmail.com> writes: I introduced it as a fallback because early revisions of Alchemy hardware we shipped had a non-functional 32kHz timer and had to rely on the r4k timer instead. Previously the r4k timer was initialized regardless, but it's useless with the "wait" instruction. So long story short: I need either the on-chip 32kHz timer OR the r4k timer if the 32kHz one is unusable, but not both, and r4k timer is useless when au1k_idle is in use. The current in-kernel Alchemy boards all work with the 32kHz timer, so I'm not against removing R4K_LIB symbols. Signed-off-by: Steven J. Hill <sjhill@mips.com> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
[ralf@linux-mips.org: Original patch by Maxim Uvarov <muvarov@gmail.com> with plenty of further shining, polishing, debugging and testing by me.] Signed-off-by: Maxim Uvarov <muvarov@gmail.com> Cc: linux-mips@linux-mips.org Cc: kexec@lists.infradead.org Cc: horms@verge.net.au Patchwork: https://patchwork.linux-mips.org/patch/1025/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Pull MIPS update from Ralf Baechle: "Cleanups and fixes for breakage that occured earlier during this merge phase. Also a few patches that didn't make the first pull request. Of those is the Alchemy work that merges code for many of the SOCs and evaluation boards thus among other code shrinkage, reduces the number of MIPS defconfigs by 5." * 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (22 commits) MIPS: SNI: Switch RM400 serial to SCCNXP driver MIPS: Remove unused empty_bad_pmd_table[] declaration. MIPS: MT: Remove kspd. MIPS: Malta: Fix section mismatch. MIPS: asm-offset.c: Delete unused irq_cpustat_t struct offsets. MIPS: Alchemy: Merge PB1100/1500 support into DB1000 code. MIPS: Alchemy: merge PB1550 support into DB1550 code MIPS: Alchemy: Single kernel for DB1200/1300/1550 MIPS: Optimize TLB refill for RI/XI configurations. MIPS: proc: Cleanup printing of ASEs. MIPS: Hardwire detection of DSP ASE Rev 2 for systems, as required. MIPS: Add detection of DSP ASE Revision 2. MIPS: Optimize pgd_init and pmd_init MIPS: perf: Add perf functionality for BMIPS5000 MIPS: perf: Split the Kconfig option CONFIG_MIPS_MT_SMP MIPS: perf: Remove unnecessary #ifdef MIPS: perf: Add cpu feature bit for PCI (performance counter interrupt) MIPS: perf: Change the "mips_perf_event" table unsupported indicator. MIPS: Align swapper_pg_dir to 64K for better TLB Refill code. vmlinux.lds.h: Allow architectures to add sections to the front of .bss ...