[PATCH 2/3] hw/char: Add Shakti UART emulation

[Vijai Kumar K <vijai@behindbytes.com>]

This is the initial implementation of Shakti UART.

TX tested and works fine. RX is untested.

Signed-off-by: Vijai Kumar K <vijai@behindbytes.com>
---
 MAINTAINERS                   |   2 +
 hw/char/meson.build           |   1 +
 hw/char/shakti_uart.c         | 204 ++++++++++++++++++++++++++++++++++
 hw/char/trace-events          |   4 +
 include/hw/char/shakti_uart.h |  74 ++++++++++++
 5 files changed, 285 insertions(+)
 create mode 100644 hw/char/shakti_uart.c
 create mode 100644 include/hw/char/shakti_uart.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 9f71c4cc3f..be084865db 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1385,7 +1385,9 @@ M: Vijai Kumar K <vijai@behindbytes.com>
 L: qemu-riscv@nongnu.org
 S: Supported
 F: hw/riscv/shakti_c.c
+F: hw/char/shakti_uart.c
 F: include/hw/riscv/shakti_c.h
+F: include/hw/char/shakti_uart.h
 
 SiFive Machines
 M: Alistair Francis <Alistair.Francis@wdc.com>
diff --git a/hw/char/meson.build b/hw/char/meson.build
index 7ba38dbd96..61c43d4b51 100644
--- a/hw/char/meson.build
+++ b/hw/char/meson.build
@@ -19,6 +19,7 @@ softmmu_ss.add(when: 'CONFIG_SERIAL', if_true: files('serial.c'))
 softmmu_ss.add(when: 'CONFIG_SERIAL_ISA', if_true: files('serial-isa.c'))
 softmmu_ss.add(when: 'CONFIG_SERIAL_PCI', if_true: files('serial-pci.c'))
 softmmu_ss.add(when: 'CONFIG_SERIAL_PCI_MULTI', if_true: files('serial-pci-multi.c'))
+softmmu_ss.add(when: 'CONFIG_SHAKTI', if_true: files('shakti_uart.c'))
 softmmu_ss.add(when: 'CONFIG_VIRTIO_SERIAL', if_true: files('virtio-console.c'))
 softmmu_ss.add(when: 'CONFIG_XEN', if_true: files('xen_console.c'))
 softmmu_ss.add(when: 'CONFIG_XILINX', if_true: files('xilinx_uartlite.c'))
diff --git a/hw/char/shakti_uart.c b/hw/char/shakti_uart.c
new file mode 100644
index 0000000000..e1c72e8747
--- /dev/null
+++ b/hw/char/shakti_uart.c
@@ -0,0 +1,204 @@
+/*
+ * SHAKTI UART
+ *
+ * Copyright (c) 2021 Vijai Kumar K <vijai@behindbytes.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/char/shakti_uart.h"
+#include "hw/qdev-properties.h"
+#include "hw/qdev-properties-system.h"
+#include "qemu/log.h"
+
+#define DEBUG_SHAKTI_UART 0
+#define DPRINTF(fmt, args...) \
+    do { \
+        if (DEBUG_SHAKTI_UART) { \
+            fprintf(stderr, "[%s]%s: " fmt , TYPE_SHAKTI_UART, \
+                                             __func__, ##args); \
+        } \
+    } while (0)
+
+static uint64_t shakti_uart_read(void *opaque, hwaddr addr, unsigned size)
+{
+    ShaktiUartState *s = opaque;
+    uint64_t retvalue = 0;
+
+    switch (addr) {
+    case SHAKTI_UART_BAUD:
+        return s->uart_baud;
+        break;
+    case SHAKTI_UART_RX:
+        retvalue = s->uart_rx;
+        qemu_chr_fe_accept_input(&s->chr);
+        s->uart_status &= ~SHAKTI_UART_STATUS_RX_NOT_EMPTY;
+        return retvalue;
+        break;
+    case SHAKTI_UART_STATUS:
+        DPRINTF("uart_status: value = 0x%x)\n", s->uart_status);
+        return s->uart_status;
+        break;
+    case SHAKTI_UART_DELAY:
+        return s->uart_delay;
+        break;
+    case SHAKTI_UART_CONTROL:
+        return s->uart_control;
+        break;
+    case SHAKTI_UART_INT_EN:
+        return s->uart_interrupt;
+        break;
+    case SHAKTI_UART_IQ_CYCLES:
+        return s->uart_iq_cycles;
+        break;
+    case SHAKTI_UART_RX_THRES:
+        return s->uart_rx_threshold;
+        break;
+    default:
+        /* Also handles TX REG which is write only */
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
+    }
+
+    return 0;
+}
+
+static void shakti_uart_write(void *opaque, hwaddr addr,
+                              uint64_t data, unsigned size)
+{
+    ShaktiUartState *s = opaque;
+    uint32_t value = data;
+    uint8_t ch;
+
+    switch (addr) {
+    case SHAKTI_UART_BAUD:
+        s->uart_baud = value;
+        break;
+    case SHAKTI_UART_TX:
+        ch = value;
+        qemu_chr_fe_write_all(&s->chr, &ch, 1);
+        s->uart_status &= ~SHAKTI_UART_STATUS_TX_FULL;
+        break;
+    case SHAKTI_UART_STATUS:
+        s->uart_status = value;
+        break;
+    case SHAKTI_UART_DELAY:
+        s->uart_delay = value;
+        break;
+    case SHAKTI_UART_CONTROL:
+        s->uart_control = value;
+        break;
+    case SHAKTI_UART_INT_EN:
+        s->uart_interrupt = value;
+        break;
+    case SHAKTI_UART_IQ_CYCLES:
+        s->uart_iq_cycles = value;
+        break;
+    case SHAKTI_UART_RX_THRES:
+        s->uart_rx_threshold = value;
+        break;
+    default:
+        /* Also handles TX REG which is write only */
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Bad offset 0x%"HWADDR_PRIx"\n", __func__, addr);
+    }
+}
+
+static const MemoryRegionOps shakti_uart_ops = {
+    .read = shakti_uart_read,
+    .write = shakti_uart_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+    .impl = {.min_access_size = 1, .max_access_size = 4},
+    .valid = {.min_access_size = 1, .max_access_size = 4},
+};
+
+static void shakti_uart_reset(DeviceState *dev)
+{
+    ShaktiUartState *s = SHAKTI_UART(dev);
+
+    s->uart_baud = SHAKTI_UART_BAUD_DEFAULT;
+    s->uart_tx = 0x0;
+    s->uart_rx = 0x0;
+    s->uart_status = 0x0000;
+    s->uart_delay = 0x0000;
+    s->uart_control = SHAKTI_UART_CONTROL_DEFAULT;
+    s->uart_interrupt = 0x0000;
+    s->uart_iq_cycles = 0x00;
+    s->uart_rx_threshold = 0x00;
+}
+
+static int shakti_uart_can_receive(void *opaque)
+{
+    return 1;
+}
+
+static void shakti_uart_receive(void *opaque, const uint8_t *buf, int size)
+{
+    ShaktiUartState *s = opaque;
+
+    s->uart_rx = *buf;
+    s->uart_status |= SHAKTI_UART_STATUS_RX_NOT_EMPTY;
+}
+
+static void shakti_uart_realize(DeviceState *dev, Error **errp)
+{
+    ShaktiUartState *sus = SHAKTI_UART(dev);
+    qemu_chr_fe_set_handlers(&sus->chr, shakti_uart_can_receive,
+                             shakti_uart_receive, NULL, NULL, sus, NULL, true);
+}
+
+static void shakti_uart_instance_init(Object *obj)
+{
+    ShaktiUartState *sus = SHAKTI_UART(obj);
+    memory_region_init_io(&sus->mmio,
+                          obj,
+                          &shakti_uart_ops,
+                          sus,
+                          TYPE_SHAKTI_UART,
+                          0x1000);
+    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &sus->mmio);
+}
+
+static Property shakti_uart_properties[] = {
+    DEFINE_PROP_CHR("chardev", ShaktiUartState, chr),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void shakti_uart_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    dc->reset = shakti_uart_reset;
+    dc->realize = shakti_uart_realize;
+    device_class_set_props(dc, shakti_uart_properties);
+}
+
+static const TypeInfo shakti_uart_info = {
+    .name = TYPE_SHAKTI_UART,
+    .parent = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(ShaktiUartState),
+    .class_init = shakti_uart_class_init,
+    .instance_init = shakti_uart_instance_init,
+};
+
+static void shakti_uart_register_types(void)
+{
+    type_register_static(&shakti_uart_info);
+}
+type_init(shakti_uart_register_types)
diff --git a/hw/char/trace-events b/hw/char/trace-events
index 81026f6612..54aeeb899c 100644
--- a/hw/char/trace-events
+++ b/hw/char/trace-events
@@ -80,6 +80,10 @@ cmsdk_apb_uart_set_params(int speed) "CMSDK APB UART: params set to %d 8N1"
 nrf51_uart_read(uint64_t addr, uint64_t r, unsigned int size) "addr 0x%" PRIx64 " value 0x%" PRIx64 " size %u"
 nrf51_uart_write(uint64_t addr, uint64_t value, unsigned int size) "addr 0x%" PRIx64 " value 0x%" PRIx64 " size %u"
 
+# shakti_uart.c
+shakti_uart_read(uint64_t addr, uint16_t r, unsigned int size) "addr 0x%" PRIx64 " value 0x%" PRIx16 " size %u"
+shakti_uart_write(uint64_t addr, uint64_t value, unsigned int size) "addr 0x%" PRIx64 " value 0x%" PRIx64 " size %u"
+
 # exynos4210_uart.c
 exynos_uart_dmabusy(uint32_t channel) "UART%d: DMA busy (Rx buffer empty)"
 exynos_uart_dmaready(uint32_t channel) "UART%d: DMA ready"
diff --git a/include/hw/char/shakti_uart.h b/include/hw/char/shakti_uart.h
new file mode 100644
index 0000000000..526c408233
--- /dev/null
+++ b/include/hw/char/shakti_uart.h
@@ -0,0 +1,74 @@
+/*
+ * SHAKTI UART
+ *
+ * Copyright (c) 2021 Vijai Kumar K <vijai@behindbytes.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef HW_SHAKTI_UART_H
+#define HW_SHAKTI_UART_H
+
+#include "hw/sysbus.h"
+#include "chardev/char-fe.h"
+
+#define SHAKTI_UART_BAUD        0x00
+#define SHAKTI_UART_TX          0x04
+#define SHAKTI_UART_RX          0x08
+#define SHAKTI_UART_STATUS      0x0C
+#define SHAKTI_UART_DELAY       0x10
+#define SHAKTI_UART_CONTROL     0x14
+#define SHAKTI_UART_INT_EN      0x18
+#define SHAKTI_UART_IQ_CYCLES   0x1C
+#define SHAKTI_UART_RX_THRES    0x20
+
+#define SHAKTI_UART_STATUS_TX_EMPTY     (1 << 0)
+#define SHAKTI_UART_STATUS_TX_FULL      (1 << 1)
+#define SHAKTI_UART_STATUS_RX_NOT_EMPTY (1 << 2)
+#define SHAKTI_UART_STATUS_RX_FULL      (1 << 3)
+/* 9600 8N1 is the default setting */
+/* Reg value = (50000000 Hz)/(16 * 9600)*/
+#define SHAKTI_UART_BAUD_DEFAULT    0x0145
+#define SHAKTI_UART_CONTROL_DEFAULT 0x0100
+
+#define TYPE_SHAKTI_UART "shakti-uart"
+#define SHAKTI_UART(obj) \
+    OBJECT_CHECK(ShaktiUartState, (obj), TYPE_SHAKTI_UART)
+
+typedef struct {
+    /* <private> */
+    SysBusDevice parent_obj;
+
+    /* <public> */
+    MemoryRegion mmio;
+
+    uint32_t uart_baud;
+    uint32_t uart_tx;
+    uint32_t uart_rx;
+    uint32_t uart_status;
+    uint32_t uart_delay;
+    uint32_t uart_control;
+    uint32_t uart_interrupt;
+    uint32_t uart_iq_cycles;
+    uint32_t uart_rx_threshold;
+
+    CharBackend chr;
+} ShaktiUartState;
+
+#endif /* HW_SHAKTI_UART_H */
-- 
2.25.1