[RFC PATCH 2/2] xen/arm: Add MESON UART driver for Amlogic S905 SoC

[Amit Singh Tomar <amittomer25@gmail.com>]

This patch adds driver for UART controller present on Amlogic S905 SoC.
https://dn.odroid.com/S905/DataSheet/S905_Public_Datasheet_V1.1.4.pdf

Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>
---
 xen/drivers/char/Kconfig      |   8 ++
 xen/drivers/char/Makefile     |   1 +
 xen/drivers/char/meson-uart.c | 290 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 299 insertions(+)
 create mode 100644 xen/drivers/char/meson-uart.c

diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig
index cc78ec3..b9fee4e 100644
--- a/xen/drivers/char/Kconfig
+++ b/xen/drivers/char/Kconfig
@@ -20,6 +20,14 @@ config HAS_MVEBU
 	  This selects the Marvell MVEBU UART. If you have a ARMADA 3700
 	  based board, say Y.
 
+config HAS_MESON
+    bool
+    default y
+    depends on ARM_64
+    help
+      This selects the Marvell MESON UART. If you have a Amlogic S905
+      based board, say Y.
+
 config HAS_PL011
 	bool
 	default y
diff --git a/xen/drivers/char/Makefile b/xen/drivers/char/Makefile
index b68c330..7c646d7 100644
--- a/xen/drivers/char/Makefile
+++ b/xen/drivers/char/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_HAS_NS16550) += ns16550.o
 obj-$(CONFIG_HAS_CADENCE_UART) += cadence-uart.o
 obj-$(CONFIG_HAS_PL011) += pl011.o
 obj-$(CONFIG_HAS_EXYNOS4210) += exynos4210-uart.o
+obj-$(CONFIG_HAS_MESON) += meson-uart.o
 obj-$(CONFIG_HAS_MVEBU) += mvebu-uart.o
 obj-$(CONFIG_HAS_OMAP) += omap-uart.o
 obj-$(CONFIG_HAS_SCIF) += scif-uart.o
diff --git a/xen/drivers/char/meson-uart.c b/xen/drivers/char/meson-uart.c
new file mode 100644
index 0000000..8fe7e62
--- /dev/null
+++ b/xen/drivers/char/meson-uart.c
@@ -0,0 +1,290 @@
+/*
+ * xen/drivers/char/meson-uart.c
+ *
+ * Driver for Amlogic MESON UART
+ *
+ * Copyright (c) 2018, Amit Singh Tomar <amittomer25@gmail.com>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms and conditions of the GNU General Public
+ * License, version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <xen/irq.h>
+#include <xen/serial.h>
+#include <xen/vmap.h>
+#include <asm/io.h>
+
+/* Register offsets */
+#define UART_WFIFO                  0x00
+#define UART_RFIFO                  0x04
+#define UART_CONTROL                0x08
+#define UART_STATUS                 0x0c
+#define UART_MISC                   0x10
+#define UART_REG5                   0x14
+
+/* UART_CONTROL bits */
+#define UART_TX_EN                  BIT(12)
+#define UART_RX_EN                  BIT(13)
+#define UART_TX_RST                 BIT(22)
+#define UART_RX_RST                 BIT(23)
+#define UART_CLEAR_ERR              BIT(24)
+#define UART_RX_INT_EN              BIT(27)
+#define UART_TX_INT_EN              BIT(28)
+
+/* UART_STATUS bits */
+#define UART_PARITY_ERR             BIT(16)
+#define UART_FRAME_ERR              BIT(17)
+#define UART_TX_FIFO_WERR           BIT(18)
+#define UART_RX_EMPTY               BIT(20)
+#define UART_TX_FULL                BIT(21)
+#define UART_TX_EMPTY               BIT(22)
+#define UART_TX_CNT_MASK            GENMASK(14, 8)
+
+
+#define UART_XMIT_IRQ_CNT_MASK      GENMASK(15, 8)
+#define UART_RECV_IRQ_CNT_MASK      GENMASK(7, 0)
+
+#define TX_FIFO_SIZE                64
+
+static struct meson_s905_uart {
+    unsigned int irq;
+    void __iomem *regs;
+    struct irqaction irqaction;
+    struct vuart_info vuart;
+} meson_s905_com = {0};
+
+#define meson_s905_read(uart, off)           readl((uart)->regs + off)
+#define meson_s905_write(uart, off, val)     writel(val, (uart->regs) + off)
+
+static void meson_s905_uart_interrupt(int irq, void *data,
+        struct cpu_user_regs *regs)
+{
+    struct serial_port *port = data;
+    struct meson_s905_uart *uart = port->uart;
+    uint32_t st = meson_s905_read(uart, UART_STATUS);
+
+    if ( !(st & UART_RX_EMPTY) )
+    {
+        serial_rx_interrupt(port, regs);
+    }
+
+    if ( !(st & UART_TX_FULL) )
+    {
+        if ( st & UART_TX_INT_EN )
+            serial_tx_interrupt(port, regs);
+    }
+
+}
+
+static void __init meson_s905_uart_init_preirq(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+    uint32_t reg;
+
+    reg = meson_s905_read(uart, UART_CONTROL);
+    reg &= ~(UART_RX_RST | UART_TX_RST | UART_CLEAR_ERR);
+    meson_s905_write(uart, UART_CONTROL, reg);
+
+    /* Disbale Rx/Tx interrupts */
+    reg = meson_s905_read(uart, UART_CONTROL);
+    reg &= ~(UART_RX_INT_EN | UART_TX_INT_EN);
+    meson_s905_write(uart, UART_CONTROL, reg);
+}
+
+static void __init meson_s905_uart_init_postirq(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+    uint32_t reg;
+
+    uart->irqaction.handler = meson_s905_uart_interrupt;
+    uart->irqaction.name    = "meson_s905_uart";
+    uart->irqaction.dev_id  = port;
+
+    if ( setup_irq(uart->irq, 0, &uart->irqaction) != 0 )
+    {
+        printk("Failed to allocated meson_s905_uart IRQ %d\n", uart->irq);
+        return;
+    }
+
+    /* Configure Rx/Tx interrupts based on bytes in FIFO */
+    reg = meson_s905_read(uart, UART_MISC);
+    reg = (UART_RECV_IRQ_CNT_MASK & 1) |
+           (UART_XMIT_IRQ_CNT_MASK & ((TX_FIFO_SIZE / 2) << 8));
+    meson_s905_write(uart, UART_MISC, reg);
+
+    /* Make sure Rx/Tx interrupts are enabled now */
+    reg = meson_s905_read(uart, UART_CONTROL);
+    reg |= (UART_RX_INT_EN | UART_TX_INT_EN);
+    meson_s905_write(uart, UART_CONTROL, reg);
+}
+
+static void meson_s905_uart_suspend(struct serial_port *port)
+{
+    BUG();
+}
+
+static void meson_s905_uart_resume(struct serial_port *port)
+{
+    BUG();
+}
+
+static void meson_s905_uart_putc(struct serial_port *port, char c)
+{
+    struct meson_s905_uart *uart = port->uart;
+
+    meson_s905_write(uart, UART_WFIFO, c);
+}
+
+static int meson_s905_uart_getc(struct serial_port *port, char *c)
+{
+    struct meson_s905_uart *uart = port->uart;
+
+    if ( (meson_s905_read(uart, UART_STATUS) & UART_RX_EMPTY) )
+        return 0;
+
+    *c =  meson_s905_read(uart, UART_RFIFO) & 0xff;
+
+    return 1;
+}
+
+static int __init meson_s905_irq(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+
+    return uart->irq;
+}
+
+static const struct vuart_info *meson_s905_vuart_info(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+
+    return &uart->vuart;
+}
+
+static void meson_s905_uart_stop_tx(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+    uint32_t reg;
+
+    reg = meson_s905_read(uart, UART_CONTROL);
+    reg &= ~UART_TX_INT_EN;
+    meson_s905_write(uart, UART_CONTROL, reg);
+}
+
+static void meson_s905_uart_start_tx(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+    uint32_t reg;
+
+    reg = meson_s905_read(uart, UART_CONTROL);
+    reg |= UART_TX_INT_EN;
+    meson_s905_write(uart, UART_CONTROL, reg);
+}
+
+static int meson_s905_uart_tx_ready(struct serial_port *port)
+{
+    struct meson_s905_uart *uart = port->uart;
+    uint32_t reg;
+
+    reg = meson_s905_read(uart, UART_STATUS);
+
+    if ( reg & UART_TX_EMPTY )
+        return TX_FIFO_SIZE;
+    if ( reg & UART_TX_FULL )
+        return 0;
+
+    return (reg & UART_TX_CNT_MASK) >> 8;
+}
+
+static struct uart_driver __read_mostly meson_uart_driver = {
+    .init_preirq  = meson_s905_uart_init_preirq,
+    .init_postirq = meson_s905_uart_init_postirq,
+    .endboot      = NULL,
+    .suspend      = meson_s905_uart_suspend,
+    .resume       = meson_s905_uart_resume,
+    .putc         = meson_s905_uart_putc,
+    .getc         = meson_s905_uart_getc,
+    .tx_ready     = meson_s905_uart_tx_ready,
+    .stop_tx      = meson_s905_uart_stop_tx,
+    .start_tx     = meson_s905_uart_start_tx,
+    .irq          = meson_s905_irq,
+    .vuart_info   = meson_s905_vuart_info,
+};
+
+static int __init meson_uart_init(struct dt_device_node *dev, const void *data)
+{
+    const char *config = data;
+    struct meson_s905_uart *uart;
+    int res;
+    u64 addr, size;
+
+    if ( strcmp(config, "") )
+        printk("WARNING: UART configuration is not supported\n");
+
+    uart = &meson_s905_com;
+
+    res = dt_device_get_address(dev, 0, &addr, &size);
+    if ( res )
+    {
+        printk("meson_s905: Unable to retrieve the base address of the UART\n");
+        return res;
+    }
+
+    res = platform_get_irq(dev, 0);
+    if ( res < 0 )
+    {
+        printk("meson_s905: Unable to retrieve the IRQ\n");
+        return -EINVAL;
+    }
+
+    uart->irq  = res;
+
+    uart->regs = ioremap_nocache(addr, size);
+    if ( !uart->regs )
+    {
+        printk("meson_s905: Unable to map the UART memory\n");
+        return -ENOMEM;
+    }
+
+    uart->vuart.base_addr = addr;
+    uart->vuart.size = size;
+    uart->vuart.data_off = UART_CONTROL;
+    uart->vuart.status_off = UART_STATUS;
+    uart->vuart.status = UART_RX_EMPTY | UART_TX_EMPTY;
+
+    /* Register with generic serial driver. */
+    serial_register_uart(SERHND_DTUART, &meson_uart_driver, uart);
+
+    dt_device_set_used_by(dev, DOMID_XEN);
+
+    return 0;
+}
+
+static const struct dt_device_match meson_dt_match[] __initconst =
+{
+    DT_MATCH_COMPATIBLE("amlogic,meson-uart"),
+    { /* sentinel */ },
+};
+
+DT_DEVICE_START(meson, "Amlogic-S905 UART", DEVICE_SERIAL)
+    .dt_match = meson_dt_match,
+    .init = meson_uart_init,
+DT_DEVICE_END
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+*/
-- 
1.9.1


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