[RFC 2/4] ARM: mstar: Add machine for MStar msc313 family SoCs

[Daniel Palmer <daniel@0x0f.com>]

Initial support for the MStar msc313 series of Cortex A7 based
IP camera SoCs.

These chips are interesting in that they contain a Cortex A7,
peripherals and system memory in a single tiny QFN package that
can be hand soldered allowing almost anyone to embed Linux
in their projects.
---
 MAINTAINERS                  |  1 +
 arch/arm/Kconfig             |  2 +
 arch/arm/Makefile            |  1 +
 arch/arm/mach-mstar/Kconfig  | 14 ++++++
 arch/arm/mach-mstar/Makefile |  1 +
 arch/arm/mach-mstar/msc313.c | 96 ++++++++++++++++++++++++++++++++++++
 6 files changed, 115 insertions(+)
 create mode 100644 arch/arm/mach-mstar/Kconfig
 create mode 100644 arch/arm/mach-mstar/Makefile
 create mode 100644 arch/arm/mach-mstar/msc313.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 252fa7171aea..b046773af438 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1959,6 +1959,7 @@ ARM/MStar SoC support
 M:	Daniel Palmer <daniel@thingy.jp>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 F:	Documentation/devicetree/bindings/arm/mstar.yaml
+F:	arch/arm/mach-mstar/
 S:	Maintained
 
 ARM/NEC MOBILEPRO 900/c MACHINE SUPPORT
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 24360211534a..c5c6d31e4301 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -760,6 +760,8 @@ source "arch/arm/mach-mmp/Kconfig"
 
 source "arch/arm/mach-moxart/Kconfig"
 
+source "arch/arm/mach-mstar/Kconfig"
+
 source "arch/arm/mach-mv78xx0/Kconfig"
 
 source "arch/arm/mach-mvebu/Kconfig"
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index c3624ca6c0bc..581e32505408 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -191,6 +191,7 @@ machine-$(CONFIG_ARCH_MXC)		+= imx
 machine-$(CONFIG_ARCH_MEDIATEK)		+= mediatek
 machine-$(CONFIG_ARCH_MILBEAUT)		+= milbeaut
 machine-$(CONFIG_ARCH_MXS)		+= mxs
+machine-$(CONFIG_ARCH_MSTAR)		+= mstar
 machine-$(CONFIG_ARCH_NOMADIK)		+= nomadik
 machine-$(CONFIG_ARCH_NPCM)		+= npcm
 machine-$(CONFIG_ARCH_NSPIRE)		+= nspire
diff --git a/arch/arm/mach-mstar/Kconfig b/arch/arm/mach-mstar/Kconfig
new file mode 100644
index 000000000000..d6b0a515da91
--- /dev/null
+++ b/arch/arm/mach-mstar/Kconfig
@@ -0,0 +1,14 @@
+menuconfig ARCH_MSTAR
+	bool "MStar SoC Support"
+	depends on ARCH_MULTI_V7
+	select ARM_GIC
+	help
+	  Support for MStar ARMv7 SoCs
+
+if ARCH_MSTAR
+
+config MACH_MSC313
+	bool "MStar MSC313(d/e) SoC support"
+	default ARCH_MSTAR
+
+endif
diff --git a/arch/arm/mach-mstar/Makefile b/arch/arm/mach-mstar/Makefile
new file mode 100644
index 000000000000..231105cdc872
--- /dev/null
+++ b/arch/arm/mach-mstar/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_MACH_MSC313) += msc313.o
\ No newline at end of file
diff --git a/arch/arm/mach-mstar/msc313.c b/arch/arm/mach-mstar/msc313.c
new file mode 100644
index 000000000000..c104635f39e4
--- /dev/null
+++ b/arch/arm/mach-mstar/msc313.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Device Tree support for MStar MSC313 SoCs
+ *
+ * Copyright (c) 2019 thingy.jp
+ * Author: Daniel Palmer <daniel@thingy.jp>
+ */
+
+#include <linux/init.h>
+#include <asm/mach/arch.h>
+#include <asm/mach/map.h>
+#include <linux/of.h>
+#include <asm/io.h>
+
+/*
+ * The IO space is remapped to the same place
+ * the vendor kernel does so that the hardcoded
+ * addresses all over the vendor drivers line up.
+ */
+
+#define MSC313_IO_PHYS		0x1f000000
+#define MSC313_IO_OFFSET	0xde000000
+#define MSC313_IO_VIRT		(MSC313_IO_PHYS + MSC313_IO_OFFSET)
+#define MSC313_IO_SIZE		0x00400000
+
+/*
+ * In the u-boot code the area these registers are in is
+ * called "L3 bridge".
+ *
+ * It's not exactly known what is the L3 bridge is but
+ * the vendor code for both u-boot and linux share calls
+ * to "flush the miu pipe". This seems to be to force pending
+ * CPU writes to memory so that the state is right before
+ * DMA capable devices try to read descriptors and data
+ * the CPU has prepared. Without doing this ethernet doesn't
+ * work reliably for example.
+ */
+
+#define MSC313_L3BRIDGE_FLUSH		0x204414
+#define MSC313_L3BRIDGE_STATUS		0x204440
+#define MSC313_L3BRIDGE_FLUSH_TRIGGER	BIT(0)
+#define MSC313_L3BRIDGE_STATUS_DONE	BIT(12)
+
+static void __iomem *miu_status;
+static void __iomem *miu_flush;
+
+static struct map_desc msc313_io_desc[] __initdata = {
+		{MSC313_IO_VIRT, __phys_to_pfn(MSC313_IO_PHYS),
+				MSC313_IO_SIZE, MT_DEVICE},
+};
+
+static void __init msc313_map_io(void)
+{
+	iotable_init(msc313_io_desc, ARRAY_SIZE(msc313_io_desc));
+	miu_flush = (void __iomem *) (msc313_io_desc[0].virtual
+			+ MSC313_L3BRIDGE_FLUSH);
+	miu_status = (void __iomem *) (msc313_io_desc[0].virtual
+			+ MSC313_L3BRIDGE_STATUS);
+}
+
+static const char * const msc313_board_dt_compat[] = {
+	"mstar,msc313",
+	NULL,
+};
+
+static DEFINE_SPINLOCK(msc313_mb_lock);
+
+static void msc313_mb(void)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&msc313_mb_lock, flags);
+	/* toggle the flush miu pipe fire bit */
+	writel_relaxed(0, miu_flush);
+	writel_relaxed(MSC313_L3BRIDGE_FLUSH_TRIGGER, miu_flush);
+	while (!(readl_relaxed(miu_status) & MSC313_L3BRIDGE_STATUS_DONE)) {
+		/* wait for flush to complete */
+	}
+	spin_unlock_irqrestore(&msc313_mb_lock, flags);
+}
+
+static void __init msc313_barriers_init(void)
+{
+	soc_mb = msc313_mb;
+}
+
+static void __init msc313_init(void)
+{
+	msc313_barriers_init();
+}
+
+DT_MACHINE_START(MSTAR_DT, "MStar MSC313 (Device Tree)")
+	.dt_compat	= msc313_board_dt_compat,
+	.init_machine = msc313_init,
+	.map_io = msc313_map_io,
+MACHINE_END
-- 
2.23.0


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