ARM: Fix dma_dcache_sync()

[mmel]

Summary

Drivers can request DMA to buffers that are not in memory represented in the vm page arrays. Because of this, store KVA of already mapped buffer to synclist and use it in dma_dcache_sync().

[jah]

sys/arm/arm/busdma_machdep-v6.c

1124–1135

Since you're storing the paddr in the sl alongside pages, why not always assign paddr to curaddr in sync_phys() and sync_buf()? Then you could always use paddr as the starting address for cache maintenance, and you won't need this function.

[mmoll]

I can at least confirm that this patch fixes the following problem on a Banana Pi Pro

Fatal kernel mode data abort: 'Translation Fault (L1)' on read
trapframe: 0xc0913ae8
FSR=00000005, FAR=00000020, spsr=20000013
r0 =c3ad3c48, r1 =c3ad3c38, r2 =00000001, r3 =00000001
r4 =00000cc0, r5 =00000000, r6 =c3b1fc00, r7 =00000000
r8 =00000040, r9 =c3ad3c00, r10=c0858c2c, r11=c0913ba8
r12=c3b31000, ssp=c0913b78, slr=c07418e8, pc =c0715f90

[ thread pid 0 tid 100000 ]
Stopped at      _bus_dmamap_sync+0x280: ldr     r0, [r5, #0x020]

[mmel]

Good catch! Moreover, sl->dataoffs becomes superfluous because we have physical address in all cases. And sorry for my delay...