[PATCH v2 1/4] serial: Add RISC-V HTIF console driver

Anup Patel
2022-01-27T06:11:55Z

Quite a few RISC-V emulators and ISS (including Spike) have host
transfer interface (HTIF) based console. This patch adds HTIF
based console driver for RISC-V platforms which depends totally
on DT node for HTIF register base address.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Reviewed-by: Rick Chen <rick@andestech.com>
---
drivers/serial/Kconfig | 8 ++
drivers/serial/Makefile | 1 +
drivers/serial/serial_htif.c | 178 +++++++++++++++++++++++++++++++++++
3 files changed, 187 insertions(+)
create mode 100644 drivers/serial/serial_htif.c

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 6c8fdda9a0..345d1881f5 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -866,6 +866,14 @@ config PXA_SERIAL
If you have a machine based on a Marvell XScale PXA2xx CPU you
can enable its onboard serial ports by enabling this option.

+config HTIF_CONSOLE
+ bool "RISC-V HTIF console support"
+ depends on DM_SERIAL && 64BIT
+ help
+ Select this to enable host transfer interface (HTIF) based serial
+ console. The HTIF device is quite common in RISC-V emulators and
+ RISC-V ISS so this driver allows using U-Boot on such platforms.
+
config SIFIVE_SERIAL
bool "SiFive UART support"
depends on DM_SERIAL
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 8168af640f..52e70aa191 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -73,6 +73,7 @@ obj-$(CONFIG_OWL_SERIAL) += serial_owl.o
obj-$(CONFIG_OMAP_SERIAL) += serial_omap.o
obj-$(CONFIG_MTK_SERIAL) += serial_mtk.o
obj-$(CONFIG_MT7620_SERIAL) += serial_mt7620.o
+obj-$(CONFIG_HTIF_CONSOLE) += serial_htif.o
obj-$(CONFIG_SIFIVE_SERIAL) += serial_sifive.o
obj-$(CONFIG_XEN_SERIAL) += serial_xen.o

diff --git a/drivers/serial/serial_htif.c b/drivers/serial/serial_htif.c
new file mode 100644
index 0000000000..5d2bf0aaeb
--- /dev/null
+++ b/drivers/serial/serial_htif.c
@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Ventana Micro Systems Inc.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <fdtdec.h>
+#include <log.h>
+#include <watchdog.h>
+#include <asm/global_data.h>
+#include <asm/io.h>
+#include <linux/compiler.h>
+#include <serial.h>
+#include <linux/err.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define HTIF_DATA_BITS 48
+#define HTIF_DATA_MASK ((1ULL << HTIF_DATA_BITS) - 1)
+#define HTIF_DATA_SHIFT 0
+#define HTIF_CMD_BITS 8
+#define HTIF_CMD_MASK ((1ULL << HTIF_CMD_BITS) - 1)
+#define HTIF_CMD_SHIFT 48
+#define HTIF_DEV_BITS 8
+#define HTIF_DEV_MASK ((1ULL << HTIF_DEV_BITS) - 1)
+#define HTIF_DEV_SHIFT 56
+
+#define HTIF_DEV_SYSTEM 0
+#define HTIF_DEV_CONSOLE 1
+
+#define HTIF_CONSOLE_CMD_GETC 0
+#define HTIF_CONSOLE_CMD_PUTC 1
+
+#if __riscv_xlen == 64
+# define TOHOST_CMD(dev, cmd, payload) \
+ (((u64)(dev) << HTIF_DEV_SHIFT) | \
+ ((u64)(cmd) << HTIF_CMD_SHIFT) | \
+ (u64)(payload))
+#else
+# define TOHOST_CMD(dev, cmd, payload) ({ \
+ if ((dev) || (cmd)) \
+ __builtin_trap(); \
+ (payload); })
+#endif
+#define FROMHOST_DEV(fromhost_value) \
+ ((u64)((fromhost_value) >> HTIF_DEV_SHIFT) & HTIF_DEV_MASK)
+#define FROMHOST_CMD(fromhost_value) \
+ ((u64)((fromhost_value) >> HTIF_CMD_SHIFT) & HTIF_CMD_MASK)
+#define FROMHOST_DATA(fromhost_value) \
+ ((u64)((fromhost_value) >> HTIF_DATA_SHIFT) & HTIF_DATA_MASK)
+
+struct htif_plat {
+ void *fromhost;
+ void *tohost;
+ int console_char;
+};
+
+static void __check_fromhost(struct htif_plat *plat)
+{
+ u64 fh = readq(plat->fromhost);
+
+ if (!fh)
+ return;
+ writeq(0, plat->fromhost);
+
+ /* this should be from the console */
+ if (FROMHOST_DEV(fh) != HTIF_DEV_CONSOLE)
+ __builtin_trap();
+ switch (FROMHOST_CMD(fh)) {
+ case HTIF_CONSOLE_CMD_GETC:
+ plat->console_char = 1 + (u8)FROMHOST_DATA(fh);
+ break;
+ case HTIF_CONSOLE_CMD_PUTC:
+ break;
+ default:
+ __builtin_trap();
+ }
+}
+
+static void __set_tohost(struct htif_plat *plat,
+ u64 dev, u64 cmd, u64 data)
+{
+ while (readq(plat->tohost))
+ __check_fromhost(plat);
+ writeq(TOHOST_CMD(dev, cmd, data), plat->tohost);
+}
+
+static int htif_serial_putc(struct udevice *dev, const char ch)
+{
+ struct htif_plat *plat = dev_get_plat(dev);
+
+ __set_tohost(plat, HTIF_DEV_CONSOLE, HTIF_CONSOLE_CMD_PUTC, ch);
+ return 0;
+}
+
+static int htif_serial_getc(struct udevice *dev)
+{
+ int ch;
+ struct htif_plat *plat = dev_get_plat(dev);
+
+ if (plat->console_char < 0)
+ __check_fromhost(plat);
+
+ if (plat->console_char >= 0) {
+ ch = plat->console_char;
+ plat->console_char = -1;
+ __set_tohost(plat, HTIF_DEV_CONSOLE, HTIF_CONSOLE_CMD_GETC, 0);
+ return (ch) ? ch - 1 : -EAGAIN;
+ }
+
+ return -EAGAIN;
+}
+
+static int htif_serial_pending(struct udevice *dev, bool input)
+{
+ struct htif_plat *plat = dev_get_plat(dev);
+
+ if (!input)
+ return 0;
+
+ if (plat->console_char < 0)
+ __check_fromhost(plat);
+
+ return (plat->console_char >= 0) ? 1 : 0;
+}
+
+static int htif_serial_probe(struct udevice *dev)
+{
+ struct htif_plat *plat = dev_get_plat(dev);
+
+ /* Queue first getc request */
+ __set_tohost(plat, HTIF_DEV_CONSOLE, HTIF_CONSOLE_CMD_GETC, 0);
+
+ return 0;
+}
+
+static int htif_serial_of_to_plat(struct udevice *dev)
+{
+ fdt_addr_t addr;
+ struct htif_plat *plat = dev_get_plat(dev);
+
+ addr = dev_read_addr_index(dev, 0);
+ if (addr == FDT_ADDR_T_NONE)
+ return -ENODEV;
+ plat->fromhost = (void *)(uintptr_t)addr;
+ plat->tohost = plat->fromhost + sizeof(u64);
+
+ addr = dev_read_addr_index(dev, 1);
+ if (addr != FDT_ADDR_T_NONE)
+ plat->tohost = (void *)(uintptr_t)addr;
+
+ plat->console_char = -1;
+
+ return 0;
+}
+
+static const struct dm_serial_ops htif_serial_ops = {
+ .putc = htif_serial_putc,
+ .getc = htif_serial_getc,
+ .pending = htif_serial_pending,
+};
+
+static const struct udevice_id htif_serial_ids[] = {
+ { .compatible = "ucb,htif0" },
+ { }
+};
+
+U_BOOT_DRIVER(serial_htif) = {
+ .name = "serial_htif",
+ .id = UCLASS_SERIAL,
+ .of_match = htif_serial_ids,
+ .of_to_plat = htif_serial_of_to_plat,
+ .plat_auto = sizeof(struct htif_plat),
+ .probe = htif_serial_probe,
+ .ops = &htif_serial_ops,
+};
--
2.25.1