ARC: [plat-hsdk]: allow to switch between AXI DMAC port configurations

We want to use DW AXI DMAC on HSDK board in our automated verification
to test cache & dma kernel code changes. This is perfect candidate
as we don't depend on any external peripherals like MMC card / USB
storage / etc.
To increase test coverage we want to test both options:
* DW AXI DMAC is connected through IOC port & dma direct ops used
* DW AXI DMAC is connected to DDR port & dma noncoherent ops used

Introduce 'arc_hsdk_axi_dmac_coherent' global variable which can be
modified by debugger (same way as we patch 'ioc_enable') to switch
between these options without recompiling the kernel.
Depend on this value we tweak memory bridge configuration and
"dma-coherent" DTS property of DW AXI DMAC.

Signed-off-by: Eugeniy Paltsev <[e-mail]>
Acked-by: Alexey Brodkin <[e-mail]>
Signed-off-by: Vineet Gupta <[e-mail]>

arch/arc/boot/dts/Makefile

···
 # for CONFIG_OF_ALL_DTBS test
 dtstree	:= $(srctree)/$(src)
 dtb-	:= $(patsubst $(dtstree)/%.dts,%.dtb, $(wildcard $(dtstree)/*.dts))
+
+# board-specific dtc flags
+DTC_FLAGS_hsdk += --pad 20

arch/arc/plat-hsdk/platform.c

···
  */
 
 #include <linux/init.h>
+#include <linux/of_fdt.h>
+#include <linux/libfdt.h>
 #include <linux/smp.h>
 #include <asm/arcregs.h>
 #include <asm/io.h>
 #include <asm/mach_desc.h>
+
+int arc_hsdk_axi_dmac_coherent __section(.data) = 0;
 
 #define ARC_CCM_UNUSED_ADDR	0x60000000
 
···
 	iowrite32(GPIO_INT_CONNECTED_MASK, (void __iomem *) GPIO_INTEN);
 }
 
+static int __init hsdk_tweak_node_coherency(const char *path, bool coherent)
+{
+	void *fdt = initial_boot_params;
+	const void *prop;
+	int node, ret;
+	bool dt_coh_set;
+
+	node = fdt_path_offset(fdt, path);
+	if (node < 0)
+		goto tweak_fail;
+
+	prop = fdt_getprop(fdt, node, "dma-coherent", &ret);
+	if (!prop && ret != -FDT_ERR_NOTFOUND)
+		goto tweak_fail;
+
+	dt_coh_set = ret != -FDT_ERR_NOTFOUND;
+	ret = 0;
+
+	/* need to remove "dma-coherent" property */
+	if (dt_coh_set && !coherent)
+		ret = fdt_delprop(fdt, node, "dma-coherent");
+
+	/* need to set "dma-coherent" property */
+	if (!dt_coh_set && coherent)
+		ret = fdt_setprop(fdt, node, "dma-coherent", NULL, 0);
+
+	if (ret < 0)
+		goto tweak_fail;
+
+	return 0;
+
+tweak_fail:
+	pr_err("failed to tweak %s to %scoherent\n", path, coherent ? "" : "non");
+	return -EFAULT;
+}
+
 enum hsdk_axi_masters {
 	M_HS_CORE = 0,
 	M_HS_RTT,
···
 
 #define CREG_PAE		((void __iomem *)(CREG_BASE + 0x180))
 #define CREG_PAE_UPDT		((void __iomem *)(CREG_BASE + 0x194))
+
+static void __init hsdk_init_memory_bridge_axi_dmac(void)
+{
+	bool coherent = !!arc_hsdk_axi_dmac_coherent;
+	u32 axi_m_slv1, axi_m_oft1;
+
+	/*
+	 * Don't tweak memory bridge configuration if we failed to tweak DTB
+	 * as we will end up in a inconsistent state.
+	 */
+	if (hsdk_tweak_node_coherency("/soc/dmac@80000", coherent))
+		return;
+
+	if (coherent) {
+		axi_m_slv1 = 0x77999999;
+		axi_m_oft1 = 0x76DCBA98;
+	} else {
+		axi_m_slv1 = 0x77777777;
+		axi_m_oft1 = 0x76543210;
+	}
+
+	writel(0x77777777, CREG_AXI_M_SLV0(M_DMAC_0));
+	writel(0xFEDCBA98, CREG_AXI_M_OFT0(M_DMAC_0));
+	writel(axi_m_slv1, CREG_AXI_M_SLV1(M_DMAC_0));
+	writel(axi_m_oft1, CREG_AXI_M_OFT1(M_DMAC_0));
+	writel(UPDATE_VAL, CREG_AXI_M_UPDT(M_DMAC_0));
+
+	writel(0x77777777, CREG_AXI_M_SLV0(M_DMAC_1));
+	writel(0xFEDCBA98, CREG_AXI_M_OFT0(M_DMAC_1));
+	writel(axi_m_slv1, CREG_AXI_M_SLV1(M_DMAC_1));
+	writel(axi_m_oft1, CREG_AXI_M_OFT1(M_DMAC_1));
+	writel(UPDATE_VAL, CREG_AXI_M_UPDT(M_DMAC_1));
+}
 
 static void __init hsdk_init_memory_bridge(void)
 {
···
 	writel(0x76543210, CREG_AXI_M_OFT1(M_GPU));
 	writel(UPDATE_VAL, CREG_AXI_M_UPDT(M_GPU));
 
-	writel(0x77777777, CREG_AXI_M_SLV0(M_DMAC_0));
-	writel(0x77777777, CREG_AXI_M_SLV1(M_DMAC_0));
-	writel(0xFEDCBA98, CREG_AXI_M_OFT0(M_DMAC_0));
-	writel(0x76543210, CREG_AXI_M_OFT1(M_DMAC_0));
-	writel(UPDATE_VAL, CREG_AXI_M_UPDT(M_DMAC_0));
-
-	writel(0x77777777, CREG_AXI_M_SLV0(M_DMAC_1));
-	writel(0x77777777, CREG_AXI_M_SLV1(M_DMAC_1));
-	writel(0xFEDCBA98, CREG_AXI_M_OFT0(M_DMAC_1));
-	writel(0x76543210, CREG_AXI_M_OFT1(M_DMAC_1));
-	writel(UPDATE_VAL, CREG_AXI_M_UPDT(M_DMAC_1));
-
 	writel(0x00000000, CREG_AXI_M_SLV0(M_DVFS));
 	writel(0x60000000, CREG_AXI_M_SLV1(M_DVFS));
 	writel(0x00000000, CREG_AXI_M_OFT0(M_DVFS));
 	writel(0x00000000, CREG_AXI_M_OFT1(M_DVFS));
 	writel(UPDATE_VAL, CREG_AXI_M_UPDT(M_DVFS));
+
+	hsdk_init_memory_bridge_axi_dmac();
 
 	/*
 	 * PAE remapping for DMA clients does not work due to an RTL bug, so