[PATCH 1/1] arm: qemu: support qfw

[Asherah Connor]

Adds support for QFW on Arm platforms by checking the device tree for a
"qemu,fw-cfg-mmio"-compatible node in arch_early_init_r and initialising
the driver if found.  Both MMIO and DMA are supported on this
architecture.

Signed-off-by: Asherah Connor <ashe at kivikakk.ee>
---

 arch/arm/Kconfig            |   1 +
 arch/arm/Makefile           |   1 +
 arch/arm/mach-qemu/Kconfig  |   2 +
 arch/arm/mach-qemu/Makefile |   1 +
 arch/arm/mach-qemu/qemu.c   | 109 ++++++++++++++++++++++++++++++++++++
 5 files changed, 114 insertions(+)
 create mode 100644 arch/arm/mach-qemu/Makefile
 create mode 100644 arch/arm/mach-qemu/qemu.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index d51abbeaf0..3841ae3ba2 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -937,6 +937,7 @@ config ARCH_QEMU
 	imply DM_RNG
 	imply DM_RTC
 	imply RTC_PL031
+	imply QFW
 
 config ARCH_RMOBILE
 	bool "Renesas ARM SoCs"
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 28b523b37c..90fc3d2d1a 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -70,6 +70,7 @@ machine-$(CONFIG_ARCH_NEXELL)		+= nexell
 machine-$(CONFIG_ARCH_OMAP2PLUS)	+= omap2
 machine-$(CONFIG_ARCH_ORION5X)		+= orion5x
 machine-$(CONFIG_ARCH_OWL)		+= owl
+machine-$(CONFIG_ARCH_QEMU)		+= qemu
 machine-$(CONFIG_ARCH_RMOBILE)		+= rmobile
 machine-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip
 machine-$(CONFIG_ARCH_S5PC1XX)		+= s5pc1xx
diff --git a/arch/arm/mach-qemu/Kconfig b/arch/arm/mach-qemu/Kconfig
index 186c3582eb..50cbfc5efe 100644
--- a/arch/arm/mach-qemu/Kconfig
+++ b/arch/arm/mach-qemu/Kconfig
@@ -19,11 +19,13 @@ config TARGET_QEMU_ARM_32BIT
 	select BOARD_LATE_INIT
 	select CPU_V7A
 	select SYS_ARCH_TIMER
+	select ARCH_EARLY_INIT_R if QFW
 
 config TARGET_QEMU_ARM_64BIT
 	bool "ARMv8, 64bit"
 	select ARM64
 	select BOARD_LATE_INIT
+	select ARCH_EARLY_INIT_R if QFW
 
 endchoice
 
diff --git a/arch/arm/mach-qemu/Makefile b/arch/arm/mach-qemu/Makefile
new file mode 100644
index 0000000000..5f5915fb6e
--- /dev/null
+++ b/arch/arm/mach-qemu/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_QFW) += qemu.o
diff --git a/arch/arm/mach-qemu/qemu.c b/arch/arm/mach-qemu/qemu.c
new file mode 100644
index 0000000000..742cf81d6e
--- /dev/null
+++ b/arch/arm/mach-qemu/qemu.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021, Asherah Connor <ashe at kivikakk.ee>
+ */
+#include <dm.h>
+#include <fdt_support.h>
+#include <qfw.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/*
+ * on Arm, qfw registers are MMIO at offsets; see
+ * https://github.com/qemu/qemu/blob/1af56296/docs/specs/fw_cfg.txt
+ */
+struct qemu_arm_fwcfg_mmio {
+	/*
+	 * Each access to the 64-bit data register can be 8/16/32/64 bits wide.
+	 */
+	union {
+		u8 data8;
+		u16 data16;
+		u32 data32;
+		u64 data64;
+	};
+	u16 selector;
+	u8 padding[6];
+	u64 dma;
+};
+
+static volatile struct qemu_arm_fwcfg_mmio *mmio;
+
+static void qemu_arm_fwcfg_read_entry_pio(uint16_t entry, uint32_t size,
+					  void *address)
+{
+	/*
+	 * using FW_CFG_INVALID selector will resume a previous read at its last
+	 * offset, otherwise read will start at 0 for new selector
+	 *
+	 * MMIO selector register is big-endian
+	 */
+	if (entry != FW_CFG_INVALID)
+		mmio->selector = cpu_to_be16(entry);
+
+	/* data register is string-preserving */
+	while (size >= 8) {
+		*(u64 *)address = mmio->data64;
+		address += 8;
+		size -= 8;
+	}
+	while (size >= 4) {
+		*(u32 *)address = mmio->data32;
+		address += 4;
+		size -= 4;
+	}
+	while (size >= 2) {
+		*(u16 *)address = mmio->data16;
+		address += 2;
+		size -= 2;
+	}
+	while (size >= 1) {
+		*(u8 *)address = mmio->data8;
+		address += 1;
+		size -= 1;
+	}
+}
+
+static void qemu_arm_fwcfg_read_entry_dma(struct fw_cfg_dma_access *dma)
+{
+	/* the DMA address register is big-endian */
+	mmio->dma = cpu_to_be64((uintptr_t)dma);
+
+	while (be32_to_cpu(dma->control) & ~FW_CFG_DMA_ERROR)
+		__asm__ __volatile__ ("yield");
+}
+
+static struct fw_cfg_arch_ops fwcfg_arm_ops = {
+	.arch_read_pio = qemu_arm_fwcfg_read_entry_pio,
+	.arch_read_dma = qemu_arm_fwcfg_read_entry_dma
+};
+
+int arch_early_init_r(void)
+{
+	/* Try to init QFW from device tree. */
+	int offset;
+	fdt32_t *reg;
+	u64 mmio_offset, mmio_size;
+	int addr_cells = fdt_address_cells(gd->fdt_blob, 0);
+	int size_cells = fdt_size_cells(gd->fdt_blob, 0);
+
+	offset = fdt_node_offset_by_compatible(gd->fdt_blob, -1,
+					       "qemu,fw-cfg-mmio");
+	if (offset >= 0) {
+		reg = (fdt32_t *)fdt_getprop(gd->fdt_blob, offset, "reg", 0);
+		if (reg) {
+			mmio_offset = fdt_read_number(reg, addr_cells);
+			reg += addr_cells;
+			mmio_size = fdt_read_number(reg, size_cells);
+
+			/* Sanity check: at least data+selector wide. */
+			if (mmio_size >= 10) {
+				mmio = (struct qemu_arm_fwcfg_mmio
+						*)mmio_offset;
+				qemu_fwcfg_init(&fwcfg_arm_ops);
+			}
+		}
+	}
+
+	return 0;
+}
-- 
2.20.1