On 4/30/2020 5:38 PM, Lu, Brent wrote:
Hi,
yes that seems bit weird. It is bit better as it does not modify common code,
but still... Maybe going back to your original idea of replacing memcpy, try
replacing it with readq? It should generate one instruction read (although it is
only for x64_64, for 32 bit kernel we would still need to do something else).
Thanks,
Amadeusz
Hi,
I've compared the assembly to see if there is clue. Both kernels are using 64-bit
mov to read register and the only difference is optimized or not. Both
implementations are looking good to me. Currently I don't have answer why
slower kernel hits the problem while optimized one survived.
1. Old kernel. Code is optimized and not able to reproduce the issue on this kernel.
(gdb) disas sst_shim32_read64
Dump of assembler code for function sst_shim32_read64:
0x000000000000096c <+0>: call 0x971 <sst_shim32_read64+5>
=> call __fentry__
0x0000000000000971 <+5>: push rbp
0x0000000000000972 <+6>: mov rbp,rsp
0x0000000000000975 <+9>: mov eax,esi
0x0000000000000977 <+11>: mov rax,QWORD PTR [rdi+rax*1]
=> perform 64-bit mov
0x000000000000097b <+15>: pop rbp
0x000000000000097c <+16>: ret
End of assembler dump.
Hi,
That's why I would suggest trying with readq, it should also generate
one instruction read x86_64 platforms, I looked a bit more and there is
fallback to generate two 32 bit reads on 32bit platforms, so my previous
concern about having to write separate handling for those platforms was
unneeded. So I would recommend checking using it.
diff --git a/sound/soc/intel/common/sst-dsp.c
b/sound/soc/intel/common/sst-dsp.c
index ec66be269b69..e96f636387d9 100644
--- a/sound/soc/intel/common/sst-dsp.c
+++ b/sound/soc/intel/common/sst-dsp.c
@@ -34,16 +34,13 @@ EXPORT_SYMBOL_GPL(sst_shim32_read);
void sst_shim32_write64(void __iomem *addr, u32 offset, u64 value)
{
- memcpy_toio(addr + offset, &value, sizeof(value));
+ writeq(value, addr + offset);
}
EXPORT_SYMBOL_GPL(sst_shim32_write64);
u64 sst_shim32_read64(void __iomem *addr, u32 offset)
{
- u64 val;
-
- memcpy_fromio(&val, addr + offset, sizeof(val));
- return val;
+ return readq(addr + offset);
}
EXPORT_SYMBOL_GPL(sst_shim32_read64);
Thanks,
Amadeusz
