MIPS: Alchemy: Determine cohereny at runtime based on cpu type

All Alchemy chips have coherent DMA, but for example the USB or AC97
peripherals on the Au1000/1500/1100 are not.
This patch uses DMA_MAYBE_COHERENT on Alchemy and sets coherentio based
on CPU type.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/6576/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/alchemy/common/setup.c

@@ -30,6 +30,7 @@
 #include <linux/jiffies.h>
 #include <linux/module.h>
 
+#include <asm/dma-coherence.h>
 #include <asm/mipsregs.h>
 #include <asm/time.h>
 
@@ -59,6 +60,15 @@ void __init plat_mem_setup(void)
 		/* Clear to obtain best system bus performance */
 		clear_c0_config(1 << 19); /* Clear Config[OD] */
 
+	hw_coherentio = 0;
+	coherentio = 1;
+	switch (alchemy_get_cputype()) {
+	case ALCHEMY_CPU_AU1000:
+	case ALCHEMY_CPU_AU1500:
+	case ALCHEMY_CPU_AU1100:
+		coherentio = 0;
+	}
+
 	board_setup();	/* board specific setup */
 
 	/* IO/MEM resources. */