drivers: Add Cadence UART driver

Add a driver for the Cadence UART which is found in Xilinx Zynq SOCs.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>

drivers/cadence/uart/cdns_console.S

+/*
+ * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+#include <arch.h>
+#include <asm_macros.S>
+#include <cadence/cdns_uart.h>
+
+        .globl  console_core_init
+        .globl  console_core_putc
+        .globl  console_core_getc
+
+	/* -----------------------------------------------
+	 * int console_core_init(unsigned long base_addr,
+	 * unsigned int uart_clk, unsigned int baud_rate)
+	 * Function to initialize the console without a
+	 * C Runtime to print debug information. This
+	 * function will be accessed by console_init and
+	 * crash reporting.
+	 * We assume that the bootloader already set up
+	 * the HW (baud, ...) and only enable the trans-
+	 * mitter and receiver here.
+	 * In: x0 - console base address
+	 *     w1 - Uart clock in Hz
+	 *     w2 - Baud rate
+	 * Out: return 1 on success else 0 on error
+	 * Clobber list : x1, x2, x3
+	 * -----------------------------------------------
+	 */
+func console_core_init
+	/* Check the input base address */
+	cbz	x0, core_init_fail
+	/* Check baud rate and uart clock for sanity */
+	cbz	w1, core_init_fail
+	cbz	w2, core_init_fail
+
+	/* RX/TX enabled & reset */
+	mov	w3, #(R_UART_CR_TX_EN | R_UART_CR_RX_EN | R_UART_CR_TXRST | R_UART_CR_RXRST)
+	str	w3, [x0, #R_UART_CR]
+
+	mov	w0, #1
+	ret
+core_init_fail:
+	mov	w0, wzr
+	ret
+endfunc console_core_init
+
+	/* --------------------------------------------------------
+	 * int console_core_putc(int c, unsigned long base_addr)
+	 * Function to output a character over the console. It
+	 * returns the character printed on success or -1 on error.
+	 * In : w0 - character to be printed
+	 *      x1 - console base address
+	 * Out : return -1 on error else return character.
+	 * Clobber list : x2
+	 * --------------------------------------------------------
+	 */
+func console_core_putc
+	/* Check the input parameter */
+	cbz	x1, putc_error
+	/* Prepend '\r' to '\n' */
+	cmp	w0, #0xA
+	b.ne	2f
+1:
+	/* Check if the transmit FIFO is full */
+	ldr	w2, [x1, #R_UART_SR]
+	tbnz	w2, #UART_SR_INTR_TFUL_BIT, 1b
+	mov	w2, #0xD
+	str	w2, [x1, #R_UART_TX]
+2:
+	/* Check if the transmit FIFO is full */
+	ldr	w2, [x1, #R_UART_SR]
+	tbnz	w2, #UART_SR_INTR_TFUL_BIT, 2b
+	str	w0, [x1, #R_UART_TX]
+	ret
+putc_error:
+	mov	w0, #-1
+	ret
+endfunc console_core_putc
+
+	/* ---------------------------------------------
+	 * int console_core_getc(unsigned long base_addr)
+	 * Function to get a character from the console.
+	 * It returns the character grabbed on success
+	 * or -1 on error.
+	 * In : x0 - console base address
+	 * Clobber list : x0, x1
+	 * ---------------------------------------------
+	 */
+func console_core_getc
+	cbz	x0, getc_error
+1:
+	/* Check if the receive FIFO is empty */
+	ldr	w1, [x0, #R_UART_SR]
+	tbnz	w1, #UART_SR_INTR_REMPTY_BIT, 1b
+	ldr	w1, [x0, #R_UART_RX]
+	mov	w0, w1
+	ret
+getc_error:
+	mov	w0, #-1
+	ret
+endfunc console_core_getc

include/drivers/cadence/cdns_uart.h

+/*
+ * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __CADENCE_UART_H__
+#define __CADENCE_UART_H__
+
+/* This is very minimalistic and will only work in QEMU.  */
+
+/* CADENCE Registers */
+#define R_UART_CR	0
+#define R_UART_CR_RXRST	(1 << 0) /* RX logic reset */
+#define R_UART_CR_TXRST	(1 << 1) /* TX logic reset */
+#define R_UART_CR_RX_EN	(1 << 2) /* RX enabled */
+#define R_UART_CR_TX_EN	(1 << 4) /* TX enabled */
+
+#define R_UART_SR		0x2C
+#define UART_SR_INTR_REMPTY_BIT	1
+#define UART_SR_INTR_TFUL_BIT	4
+
+#define R_UART_TX	0x30
+#define R_UART_RX	0x30
+
+#endif