Add Raspberry PI's mini-UART

devices/kernel.mk

@@ -5,7 +5,8 @@ include $(BASEDIR)/header.mk
 
 OBJS_$(d) := $(d)/pl011.o \
 	$(d)/pl110.o \
-	$(d)/pl111.o
+	$(d)/pl111.o \
+	$(d)/pi_mini_uart.o
 
 KOBJS += $(OBJS_$(d))
 

devices/pi_mini_uart.c

@@ -0,0 +1,105 @@
+/*
+    Copyright (C) 2012, Aaron Lindsay <aaron@aclindsay.com>
+
+    This file is part of Aedrix.
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    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, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <types.h>
+
+#define VC_MMU_IO_OFFSET(addr) (addr - 0x7E000000 + 0x20000000)
+
+/* Auxiliary IO registers (includes both mini-UART and SPI) */
+#define AUX_IRQ VC_MMU_IO_OFFSET(0x7E215000)
+#define AUX_ENABLES VC_MMU_IO_OFFSET(0x7E215004)
+#define AUX_MU_IO_REG VC_MMU_IO_OFFSET(0x7E215040)
+#define AUX_MU_IER_REG VC_MMU_IO_OFFSET(0x7E215044)
+#define AUX_MU_IIR_REG VC_MMU_IO_OFFSET(0x7E215048)
+#define AUX_MU_LCR_REG VC_MMU_IO_OFFSET(0x7E21504C)
+#define AUX_MU_MCR_REG VC_MMU_IO_OFFSET(0x7E215050)
+#define AUX_MU_LSR_REG VC_MMU_IO_OFFSET(0x7E215054)
+#define AUX_MU_MSR_REG VC_MMU_IO_OFFSET(0x7E215058)
+#define AUX_MU_SCRATCH VC_MMU_IO_OFFSET(0x7E21505C)
+#define AUX_MU_CNTL_REG VC_MMU_IO_OFFSET(0x7E215060)
+#define AUX_MU_STAT_REG VC_MMU_IO_OFFSET(0x7E215064)
+#define AUX_MU_BAUD_REG VC_MMU_IO_OFFSET(0x7E215068)
+#define AUX_SPI0_CNTL0_REG VC_MMU_IO_OFFSET(0x7E215080)
+#define AUX_SPI0_CNTL1_REG VC_MMU_IO_OFFSET(0x7E215084)
+#define AUX_SPI0_STAT_REG VC_MMU_IO_OFFSET(0x7E215088)
+#define AUX_SPI0_IO_REG VC_MMU_IO_OFFSET(0x7E215090)
+#define AUX_SPI0_PEEK_REG VC_MMU_IO_OFFSET(0x7E215094)
+#define AUX_SPI1_CNTL0_REG VC_MMU_IO_OFFSET(0x7E2150C0)
+#define AUX_SPI1_CNTL1_REG VC_MMU_IO_OFFSET(0x7E2150C4)
+#define AUX_SPI1_STAT_REG VC_MMU_IO_OFFSET(0x7E2150C8)
+#define AUX_SPI1_IO_REG VC_MMU_IO_OFFSET(0x7E2150D0)
+#define AUX_SPI1_PEEK_REG VC_MMU_IO_OFFSET(0x7E2150D4)
+
+/* Constants for mini-UART operation */
+#define MINI_UART_TX_EMPTY 0x20
+
+/* General GPIO pin registers */
+#define GPFSEL1 VC_MMU_IO_OFFSET(0x7E200004)
+#define GPSET0 VC_MMU_IO_OFFSET(0x7E20001C)
+#define GPCLR0 VC_MMU_IO_OFFSET(0x7E200028)
+#define GPPUD VC_MMU_IO_OFFSET(0x7E200094)
+#define GPPUDCLK0 VC_MMU_IO_OFFSET(0x7E200098)
+
+void mini_uart_init() {
+	uint32 aux_enables;
+	uint32 gpfsel1;
+	unsigned int i;
+
+	/* Enable the mini-UART */
+	aux_enables = (*(uint32 *)AUX_ENABLES) & 0x7;
+	*(uint32 *)AUX_ENABLES = aux_enables | 0x1;
+
+	//TODO are these all necessary?
+	*(uint32 *)AUX_MU_IER_REG = 0; //disable interrupts
+	*(uint32 *)AUX_MU_CNTL_REG = 0; //disable RX and TX
+	*(uint32 *)AUX_MU_LCR_REG = 3; //set to 8-bit mode (though this only takes setting bit 0, no clue why bit 1 is set too)
+	*(uint32 *)AUX_MU_MCR_REG = 0; //"If clear the UART1_RTS line is high If set the UART1_RTS line is low"
+	*(uint32 *)AUX_MU_IER_REG = 0; //disable interrupts again?
+	*(uint32 *)AUX_MU_IIR_REG = 0xC6; //why are we setting the interrupt status - this looks like a read-only register?
+					//also, the manual says setting bits 2&3 simultaneously shouldn't be possible...
+
+	// baudrate = system_clock_freq / ( 8 * (baudrate_reg + 1))
+	// baudrate_reg = system_clock_freq / baudrate / 8 - 1
+	// baudrate_reg = 250000000 / 115200 / 8 - 1 = 270
+	*(uint32 *)AUX_MU_BAUD_REG = 270;
+
+	//set the GPIO pin to the alternate function for this UART
+	gpfsel1 = (*(uint32 *)GPFSEL1) & ~(7<<12); //get the GPIO Function Select 1 register, and keep all the bits except those that are for GPIO pin 14
+	gpfsel1 |= 2<<12; // set to 010 (GPIO Pin 14 takes alternate function 5)
+	*(uint32 *)GPFSEL1 = gpfsel1;
+
+	//Follow the procedure for change pull-up/pull-down status (see page 101 of the BCM2835 ARM Peripherals datasheet)
+	*(uint32 *)GPPUD = 0; //disable pull-up/pull-down for those pins which receive a write to their bit in GPPUDCLK0/1
+	for(i = 0; i < 150; i++) asm(""); //wait at least 150 cycles
+	*(uint32 *)GPPUDCLK0 = 1<<14; //"Write to GPPUDCLK0/1 to clock the control signal into the GPIO pads you wish to modify" (in our case, this is 14)
+	for(i = 0; i < 150; i++) asm(""); //wait at least 150 cycles
+//	*(uint32 *)GPPUD = 0; //remove the signal (shouldn't really be necessary since it was 0 anyway in our case)
+	*(uint32 *)GPPUDCLK0 = 0; //clear the clock
+
+	*(uint32 *)AUX_MU_CNTL_REG = 2; //enable TX
+}
+
+void mini_uart_putc(char c) {
+	/* Wait until the serial buffer is empty */
+	while (!(*(volatile uint32*)AUX_MU_LSR_REG & MINI_UART_TX_EMPTY));
+
+	/* When it's empty, write our character */
+	*(volatile uint32*)AUX_MU_IO_REG = c;
+}

include/devices/pi_mini_uart.h

@@ -0,0 +1,27 @@
+/*
+    Copyright (C) 2012, Aaron Lindsay <aaron@aclindsay.com>
+
+    This file is part of Aedrix.
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    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, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef PI_MINI_UART_H
+#define PI_MINI_UART_H
+
+void mini_uart_init();
+void mini_uart_putc(char c);
+
+#endif /* PI_MINI_UART_H */