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/Kconfig

@@ -63,6 +63,7 @@ config MIPS_ALCHEMY
 	select CEVT_R4K
 	select CSRC_R4K
 	select IRQ_CPU
+	select DMA_MAYBE_COHERENT	# Au1000,1500,1100 aren't, rest is
 	select SYS_HAS_CPU_MIPS32_R1
 	select SYS_SUPPORTS_32BIT_KERNEL
 	select SYS_SUPPORTS_APM_EMULATION

arch/mips/alchemy/Kconfig

@@ -20,7 +20,6 @@ choice
 
 config MIPS_MTX1
 	bool "4G Systems MTX-1 board"
-	select DMA_NONCOHERENT
 	select HW_HAS_PCI
 	select ALCHEMY_GPIOINT_AU1000
 	select SYS_SUPPORTS_LITTLE_ENDIAN
@@ -29,7 +28,6 @@ config MIPS_MTX1
 config MIPS_DB1000
 	bool "Alchemy DB1000/DB1500/DB1100 PB1500/1100 boards"
 	select ALCHEMY_GPIOINT_AU1000
-	select DMA_NONCOHERENT
 	select HW_HAS_PCI
 	select SYS_SUPPORTS_BIG_ENDIAN
 	select SYS_SUPPORTS_LITTLE_ENDIAN
@@ -39,13 +37,11 @@ config MIPS_DB1235
 	bool "Alchemy DB1200/PB1200/DB1300/DB1550/PB1550 boards"
 	select ARCH_REQUIRE_GPIOLIB
 	select HW_HAS_PCI
-	select DMA_COHERENT
 	select SYS_SUPPORTS_LITTLE_ENDIAN
 	select SYS_HAS_EARLY_PRINTK
 
 config MIPS_XXS1500
 	bool "MyCable XXS1500 board"
-	select DMA_NONCOHERENT
 	select ALCHEMY_GPIOINT_AU1000
 	select SYS_SUPPORTS_LITTLE_ENDIAN
 	select SYS_HAS_EARLY_PRINTK
@@ -54,7 +50,6 @@ config MIPS_GPR
 	bool "Trapeze ITS GPR board"
 	select ALCHEMY_GPIOINT_AU1000
 	select HW_HAS_PCI
-	select DMA_NONCOHERENT
 	select SYS_SUPPORTS_LITTLE_ENDIAN
 	select SYS_HAS_EARLY_PRINTK
 

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. */

arch/mips/pci/pci-alchemy.c

@@ -16,6 +16,7 @@
 #include <linux/syscore_ops.h>
 #include <linux/vmalloc.h>
 
+#include <asm/dma-coherence.h>
 #include <asm/mach-au1x00/au1000.h>
 #include <asm/tlbmisc.h>
 
@@ -411,17 +412,15 @@ static int alchemy_pci_probe(struct platform_device *pdev)
 	}
 	ctx->alchemy_pci_ctrl.io_map_base = (unsigned long)virt_io;
 
-#ifdef CONFIG_DMA_NONCOHERENT
 	/* Au1500 revisions older than AD have borked coherent PCI */
 	if ((alchemy_get_cputype() == ALCHEMY_CPU_AU1500) &&
-	    (read_c0_prid() < 0x01030202)) {
+	    (read_c0_prid() < 0x01030202) && !coherentio) {
 		val = __raw_readl(ctx->regs + PCI_REG_CONFIG);
 		val |= PCI_CONFIG_NC;
 		__raw_writel(val, ctx->regs + PCI_REG_CONFIG);
 		wmb();
 		dev_info(&pdev->dev, "non-coherent PCI on Au1500 AA/AB/AC\n");
 	}
-#endif
 
 	if (pd->board_map_irq)
 		ctx->board_map_irq = pd->board_map_irq;