xtensa: xtfpga: fix hardware lockup caused by LCD driver

LCD driver is always built for the XTFPGA platform, but its base address
is not configurable, and is wrong for ML605/KC705. Its initialization
locks up KC705 board hardware.

Make the whole driver optional, and its base address and bus width
configurable. Implement 4-bit bus access method.

Cc: [e-mail]
Signed-off-by: Max Filippov <[e-mail]>

arch/xtensa/Kconfig

···
 
 	  If unsure, leave the default value here.
 
+config XTFPGA_LCD
+	bool "Enable XTFPGA LCD driver"
+	depends on XTENSA_PLATFORM_XTFPGA
+	default n
+	help
+	  There's a 2x16 LCD on most of XTFPGA boards, kernel may output
+	  progress messages there during bootup/shutdown. It may be useful
+	  during board bringup.
+
+	  If unsure, say N.
+
+config XTFPGA_LCD_BASE_ADDR
+	hex "XTFPGA LCD base address"
+	depends on XTFPGA_LCD
+	default "0x0d0c0000"
+	help
+	  Base address of the LCD controller inside KIO region.
+	  Different boards from XTFPGA family have LCD controller at different
+	  addresses. Please consult prototyping user guide for your board for
+	  the correct address. Wrong address here may lead to hardware lockup.
+
+config XTFPGA_LCD_8BIT_ACCESS
+	bool "Use 8-bit access to XTFPGA LCD"
+	depends on XTFPGA_LCD
+	default n
+	help
+	  LCD may be connected with 4- or 8-bit interface, 8-bit access may
+	  only be used with 8-bit interface. Please consult prototyping user
+	  guide for your board for the correct interface width.
+
 endmenu
 
 menu "Executable file formats"

arch/xtensa/platforms/xtfpga/Makefile

···
 #
 # Note 2! The CFLAGS definitions are in the main makefile...
 
-obj-y			= setup.o lcd.o
+obj-y			+= setup.o
+obj-$(CONFIG_XTFPGA_LCD) += lcd.o

arch/xtensa/platforms/xtfpga/include/platform/hardware.h

···
 
 /* UART */
 #define DUART16552_PADDR	(XCHAL_KIO_PADDR + 0x0D050020)
-/* LCD instruction and data addresses. */
-#define LCD_INSTR_ADDR		((char *)IOADDR(0x0D040000))
-#define LCD_DATA_ADDR		((char *)IOADDR(0x0D040004))
 
 /* Misc. */
 #define XTFPGA_FPGAREGS_VADDR	IOADDR(0x0D020000)

arch/xtensa/platforms/xtfpga/include/platform/lcd.h

···
 #ifndef __XTENSA_XTAVNET_LCD_H
 #define __XTENSA_XTAVNET_LCD_H
 
+#ifdef CONFIG_XTFPGA_LCD
 /* Display string STR at position POS on the LCD. */
 void lcd_disp_at_pos(char *str, unsigned char pos);
 
 /* Shift the contents of the LCD display left or right. */
 void lcd_shiftleft(void);
 void lcd_shiftright(void);
+#else
+static inline void lcd_disp_at_pos(char *str, unsigned char pos)
+{
+}
+
+static inline void lcd_shiftleft(void)
+{
+}
+
+static inline void lcd_shiftright(void)
+{
+}
+#endif
+
 #endif

arch/xtensa/platforms/xtfpga/lcd.c

···
 /*
- * Driver for the LCD display on the Tensilica LX60 Board.
+ * Driver for the LCD display on the Tensilica XTFPGA board family.
+ * http://www.mytechcorp.com/cfdata/productFile/File1/MOC-16216B-B-A0A04.pdf
  *
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * Copyright (C) 2001, 2006 Tensilica Inc.
+ * Copyright (C) 2015 Cadence Design Systems Inc.
  */
 
-/*
- *
- * FIXME: this code is from the examples from the LX60 user guide.
- *
- * The lcd_pause function does busy waiting, which is probably not
- * great. Maybe the code could be changed to use kernel timers, or
- * change the hardware to not need to wait.
- */
-
+#include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/io.h>
 
 #include <platform/hardware.h>
 #include <platform/lcd.h>
-#include <linux/delay.h>
 
-#define LCD_PAUSE_ITERATIONS	4000
+/* LCD instruction and data addresses. */
+#define LCD_INSTR_ADDR		((char *)IOADDR(CONFIG_XTFPGA_LCD_BASE_ADDR))
+#define LCD_DATA_ADDR		(LCD_INSTR_ADDR + 4)
+
 #define LCD_CLEAR		0x1
 #define LCD_DISPLAY_ON		0xc
 
 /* 8bit and 2 lines display */
 #define LCD_DISPLAY_MODE8BIT	0x38
+#define LCD_DISPLAY_MODE4BIT	0x28
 #define LCD_DISPLAY_POS		0x80
 #define LCD_SHIFT_LEFT		0x18
 #define LCD_SHIFT_RIGHT		0x1c
 
+static void lcd_put_byte(u8 *addr, u8 data)
+{
+#ifdef CONFIG_XTFPGA_LCD_8BIT_ACCESS
+	ACCESS_ONCE(*addr) = data;
+#else
+	ACCESS_ONCE(*addr) = data & 0xf0;
+	ACCESS_ONCE(*addr) = (data << 4) & 0xf0;
+#endif
+}
+
 static int __init lcd_init(void)
 {
-	*LCD_INSTR_ADDR = LCD_DISPLAY_MODE8BIT;
+	ACCESS_ONCE(*LCD_INSTR_ADDR) = LCD_DISPLAY_MODE8BIT;
 	mdelay(5);
-	*LCD_INSTR_ADDR = LCD_DISPLAY_MODE8BIT;
+	ACCESS_ONCE(*LCD_INSTR_ADDR) = LCD_DISPLAY_MODE8BIT;
 	udelay(200);
-	*LCD_INSTR_ADDR = LCD_DISPLAY_MODE8BIT;
+	ACCESS_ONCE(*LCD_INSTR_ADDR) = LCD_DISPLAY_MODE8BIT;
 	udelay(50);
-	*LCD_INSTR_ADDR = LCD_DISPLAY_ON;
+#ifndef CONFIG_XTFPGA_LCD_8BIT_ACCESS
+	ACCESS_ONCE(*LCD_INSTR_ADDR) = LCD_DISPLAY_MODE4BIT;
 	udelay(50);
-	*LCD_INSTR_ADDR = LCD_CLEAR;
+	lcd_put_byte(LCD_INSTR_ADDR, LCD_DISPLAY_MODE4BIT);
+	udelay(50);
+#endif
+	lcd_put_byte(LCD_INSTR_ADDR, LCD_DISPLAY_ON);
+	udelay(50);
+	lcd_put_byte(LCD_INSTR_ADDR, LCD_CLEAR);
 	mdelay(10);
 	lcd_disp_at_pos("XTENSA LINUX", 0);
 	return 0;
···
 
 void lcd_disp_at_pos(char *str, unsigned char pos)
 {
-	*LCD_INSTR_ADDR = LCD_DISPLAY_POS | pos;
+	lcd_put_byte(LCD_INSTR_ADDR, LCD_DISPLAY_POS | pos);
 	udelay(100);
 	while (*str != 0) {
-		*LCD_DATA_ADDR = *str;
+		lcd_put_byte(LCD_DATA_ADDR, *str);
 		udelay(200);
 		str++;
 	}
···
 
 void lcd_shiftleft(void)
 {
-	*LCD_INSTR_ADDR = LCD_SHIFT_LEFT;
+	lcd_put_byte(LCD_INSTR_ADDR, LCD_SHIFT_LEFT);
 	udelay(50);
 }
 
 void lcd_shiftright(void)
 {
-	*LCD_INSTR_ADDR = LCD_SHIFT_RIGHT;
+	lcd_put_byte(LCD_INSTR_ADDR, LCD_SHIFT_RIGHT);
 	udelay(50);
 }