hw/char: avr: Add limited support for USART peripheral

These were designed to facilitate testing but should provide enough
function to be useful in other contexts.  Only a subset of the functions
of each peripheral is implemented, mainly due to the lack of a standard
way to handle electrical connections (like GPIO pins).

[AM: Remove word 'Atmel' from filenames and all elements of code]
Suggested-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Signed-off-by: Michael Rolnik <mrolnik@gmail.com>
Signed-off-by: Sarah Harris <S.E.Harris@kent.ac.uk>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[rth: Squash I/O size fix and file rename from f4bug]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Reviewed-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Signed-off-by: Thomas Huth <huth@tuxfamily.org>
Message-Id: <20200705140315.260514-20-huth@tuxfamily.org>

1 files changed, 93 insertions, 0 deletions

diff --git a/include/hw/char/avr_usart.h b/include/hw/char/avr_usart.h
new file mode 100644
index 0000000000..5739aaf26f
--- /dev/null
+++ b/include/hw/char/avr_usart.h
@@ -0,0 +1,93 @@
+/*
+ * AVR USART
+ *
+ * Copyright (c) 2018 University of Kent
+ * Author: Sarah Harris
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see
+ * <http://www.gnu.org/licenses/lgpl-2.1.html>
+ */
+
+#ifndef HW_CHAR_AVR_USART_H
+#define HW_CHAR_AVR_USART_H
+
+#include "hw/sysbus.h"
+#include "chardev/char-fe.h"
+#include "hw/hw.h"
+
+/* Offsets of registers. */
+#define USART_DR   0x06
+#define USART_CSRA  0x00
+#define USART_CSRB  0x01
+#define USART_CSRC  0x02
+#define USART_BRRH 0x05
+#define USART_BRRL 0x04
+
+/* Relevant bits in regiters. */
+#define USART_CSRA_RXC    (1 << 7)
+#define USART_CSRA_TXC    (1 << 6)
+#define USART_CSRA_DRE    (1 << 5)
+#define USART_CSRA_MPCM   (1 << 0)
+
+#define USART_CSRB_RXCIE  (1 << 7)
+#define USART_CSRB_TXCIE  (1 << 6)
+#define USART_CSRB_DREIE  (1 << 5)
+#define USART_CSRB_RXEN   (1 << 4)
+#define USART_CSRB_TXEN   (1 << 3)
+#define USART_CSRB_CSZ2   (1 << 2)
+#define USART_CSRB_RXB8   (1 << 1)
+#define USART_CSRB_TXB8   (1 << 0)
+
+#define USART_CSRC_MSEL1  (1 << 7)
+#define USART_CSRC_MSEL0  (1 << 6)
+#define USART_CSRC_PM1    (1 << 5)
+#define USART_CSRC_PM0    (1 << 4)
+#define USART_CSRC_CSZ1   (1 << 2)
+#define USART_CSRC_CSZ0   (1 << 1)
+
+#define TYPE_AVR_USART "avr-usart"
+#define AVR_USART(obj) \
+    OBJECT_CHECK(AVRUsartState, (obj), TYPE_AVR_USART)
+
+typedef struct {
+    /* <private> */
+    SysBusDevice parent_obj;
+
+    /* <public> */
+    MemoryRegion mmio;
+
+    CharBackend chr;
+
+    bool enabled;
+
+    uint8_t data;
+    bool data_valid;
+    uint8_t char_mask;
+    /* Control and Status Registers */
+    uint8_t csra;
+    uint8_t csrb;
+    uint8_t csrc;
+    /* Baud Rate Registers (low/high byte) */
+    uint8_t brrh;
+    uint8_t brrl;
+
+    /* Receive Complete */
+    qemu_irq rxc_irq;
+    /* Transmit Complete */
+    qemu_irq txc_irq;
+    /* Data Register Empty */
+    qemu_irq dre_irq;
+} AVRUsartState;
+
+#endif /* HW_CHAR_AVR_USART_H */