drivers: dma-coherent: use memset_io for DMA_MEMORY_IO mappings

Use memset_io() for DMA_MEMORY_IO mappings which are mapped as I/O
memory, and regular memset() for DMA_MEMORY_MAP mappings.

This fixes the below alignment fault on arm64 for DMA_MEMORY_IO
mappings, where memset() uses the DC ZVA instruction which is invalid on
device memory.

Unhandled fault: alignment fault (0x96000061) at 0xffffff8000380000
Internal error: : 96000061 [#1] PREEMPT SMP
Modules linked in: hdlcd(+) clk_scpi
CPU: 4 PID: 1355 Comm: systemd-udevd Not tainted 4.4.0-rc1+ #5
Hardware name: ARM Juno development board (r0) (DT)
task: ffffffc9763eee00 ti: ffffffc9758c4000 task.ti: ffffffc9758c4000
PC is at __efistub_memset+0x1ac/0x200
LR is at dma_alloc_from_coherent+0xb0/0x120
pc : [<ffffffc00030ff2c>] lr : [<ffffffc00042a918>] pstate: 400001c5
sp : ffffffc9758c79a0
x29: ffffffc9758c79a0 x28: ffffffc000635cd0
x27: 0000000000000124 x26: ffffffc000119ef4
x25: 0000000000010000 x24: 0000000000000140
x23: ffffffc07e9ac3a8 x22: ffffffc9758c7a58
x21: ffffffc9758c7a68 x20: 0000000000000004
x19: ffffffc07e9ac380 x18: 0000000000000001
x17: 0000007fae1bbba8 x16: ffffffc0001b2d1c
x15: ffffffffffffffff x14: 0ffffffffffffffe
x13: 0000000000000010 x12: ffffff800837ffff
x11: ffffff800837ffff x10: 0000000040000000
x9 : 0000000000000000 x8 : ffffff8000380000
x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : 0000000000000000
x3 : 0000000000000004 x2 : 000000000000ffc0
x1 : 0000000000000000 x0 : ffffff8000380000

Signed-off-by: Brian Starkey <[e-mail]>
Reviewed-by: Catalin Marinas <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/base/dma-coherent.c

···
 	 */
 	*dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
 	*ret = mem->virt_base + (pageno << PAGE_SHIFT);
-	memset(*ret, 0, size);
+	if (mem->flags & DMA_MEMORY_MAP)
+		memset(*ret, 0, size);
+	else
+		memset_io(*ret, 0, size);
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 
 	return 1;