linux/arch/arm/mach-tegra/include/mach/uncompress.h
Stephen Warren 80881dae52 ARM: tegra: uncompress.h: Implement TEGRA_DEBUG_UART_AUTO_ODMDATA
Tegra has 5 UARTS which could be used for low-level debug output. Commit
fe26398 "ARM: tegra: uncompress.h: Choose a UART at runtime" implemented
one method for the kernel to automatically determine which of these to
use at run-time, so that the same DEBUG_LL-enabled kernel image could be
used across multiple Tegra boards. The required bootloader-side setup for
that option is implemented in NVIDIA's various downstream U-Boot branches,
but the U-Boot maintainers have refused to accept it upstream.

This change implements an alternative automatic UART selection option
using ODMDATA. This is a 32-bit value programmed into Tegra's boot memory
which provides a few pieces of basic board-specific information, including
a field that indicates the console UART. Setting up this value is part of
the standard Tegra boot architecture, and so requires no Tegra-specific
hacks in the bootloader's UART driver.

Note that in theory, the format of ODMDATA is board-specific. However, in
practice all boards use the same location/size/values for the UART field.
ODMDATA[19:18] (which drive the type of debug console) is more problematic,
since some boards use value 2 for UART and others use 3. This patch just
accepts either value; if this doesn't work well for a given board, I'd
suggest simply not enabling this debug option when building for that board.

Note that the kernel assumes the bootloader has already set up any required
pinmux settings for the UART; there is no way the kernel can do this for
itself prior to knowing which board it's running on. In practice, people
using this feature are highly likely to be using bootloaders that have
indeed configured the pinmux. This assumption existed prior to this patch.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2012-04-10 13:41:36 -06:00

237 lines
5.0 KiB
C

/*
* arch/arm/mach-tegra/include/mach/uncompress.h
*
* Copyright (C) 2010 Google, Inc.
* Copyright (C) 2011 Google, Inc.
* Copyright (C) 2011-2012 NVIDIA CORPORATION. All Rights Reserved.
*
* Author:
* Colin Cross <ccross@google.com>
* Erik Gilling <konkers@google.com>
* Doug Anderson <dianders@chromium.org>
* Stephen Warren <swarren@nvidia.com>
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* 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.
*
*/
#ifndef __MACH_TEGRA_UNCOMPRESS_H
#define __MACH_TEGRA_UNCOMPRESS_H
#include <linux/types.h>
#include <linux/serial_reg.h>
#include <mach/iomap.h>
#include <mach/irammap.h>
#define BIT(x) (1 << (x))
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
#define DEBUG_UART_SHIFT 2
volatile u8 *uart;
static void putc(int c)
{
if (uart == NULL)
return;
while (!(uart[UART_LSR << DEBUG_UART_SHIFT] & UART_LSR_THRE))
barrier();
uart[UART_TX << DEBUG_UART_SHIFT] = c;
}
static inline void flush(void)
{
}
static inline void save_uart_address(void)
{
u32 *buf = (u32 *)(TEGRA_IRAM_BASE + TEGRA_IRAM_DEBUG_UART_OFFSET);
if (uart) {
buf[0] = TEGRA_IRAM_DEBUG_UART_COOKIE;
buf[1] = (u32)uart;
} else
buf[0] = 0;
}
static const struct {
u32 base;
u32 reset_reg;
u32 clock_reg;
u32 bit;
} uarts[] = {
{
TEGRA_UARTA_BASE,
TEGRA_CLK_RESET_BASE + 0x04,
TEGRA_CLK_RESET_BASE + 0x10,
6,
},
{
TEGRA_UARTB_BASE,
TEGRA_CLK_RESET_BASE + 0x04,
TEGRA_CLK_RESET_BASE + 0x10,
7,
},
{
TEGRA_UARTC_BASE,
TEGRA_CLK_RESET_BASE + 0x08,
TEGRA_CLK_RESET_BASE + 0x14,
23,
},
{
TEGRA_UARTD_BASE,
TEGRA_CLK_RESET_BASE + 0x0c,
TEGRA_CLK_RESET_BASE + 0x18,
1,
},
{
TEGRA_UARTE_BASE,
TEGRA_CLK_RESET_BASE + 0x0c,
TEGRA_CLK_RESET_BASE + 0x18,
2,
},
};
static inline bool uart_clocked(int i)
{
if (*(u8 *)uarts[i].reset_reg & BIT(uarts[i].bit))
return false;
if (!(*(u8 *)uarts[i].clock_reg & BIT(uarts[i].bit)))
return false;
return true;
}
#ifdef CONFIG_TEGRA_DEBUG_UART_AUTO_ODMDATA
int auto_odmdata(void)
{
volatile u32 *pmc = (volatile u32 *)TEGRA_PMC_BASE;
u32 odmdata = pmc[0xa0 / 4];
/*
* Bits 19:18 are the console type: 0=default, 1=none, 2==DCC, 3==UART
* Some boards apparently swap the last two values, but we don't have
* any way of catering for that here, so we just accept either. If this
* doesn't make sense for your board, just don't enable this feature.
*
* Bits 17:15 indicate the UART to use, 0/1/2/3/4 are UART A/B/C/D/E.
*/
switch ((odmdata >> 18) & 3) {
case 2:
case 3:
break;
default:
return -1;
}
return (odmdata >> 15) & 7;
}
#endif
#ifdef CONFIG_TEGRA_DEBUG_UART_AUTO_SCRATCH
int auto_scratch(void)
{
int i;
/*
* Look for the first UART that:
* a) Is not in reset.
* b) Is clocked.
* c) Has a 'D' in the scratchpad register.
*
* Note that on Tegra30, the first two conditions are required, since
* if not true, accesses to the UART scratch register will hang.
* Tegra20 doesn't have this issue.
*
* The intent is that the bootloader will tell the kernel which UART
* to use by setting up those conditions. If nothing found, we'll fall
* back to what's specified in TEGRA_DEBUG_UART_BASE.
*/
for (i = 0; i < ARRAY_SIZE(uarts); i++) {
if (!uart_clocked(i))
continue;
uart = (volatile u8 *)uarts[i].base;
if (uart[UART_SCR << DEBUG_UART_SHIFT] != 'D')
continue;
return i;
}
return -1;
}
#endif
/*
* Setup before decompression. This is where we do UART selection for
* earlyprintk and init the uart_base register.
*/
static inline void arch_decomp_setup(void)
{
int uart_id, auto_uart_id;
volatile u32 *apb_misc = (volatile u32 *)TEGRA_APB_MISC_BASE;
u32 chip, div;
#if defined(CONFIG_TEGRA_DEBUG_UARTA)
uart_id = 0;
#elif defined(CONFIG_TEGRA_DEBUG_UARTB)
uart_id = 1;
#elif defined(CONFIG_TEGRA_DEBUG_UARTC)
uart_id = 2;
#elif defined(CONFIG_TEGRA_DEBUG_UARTD)
uart_id = 3;
#elif defined(CONFIG_TEGRA_DEBUG_UARTE)
uart_id = 4;
#else
uart_id = -1;
#endif
#if defined(CONFIG_TEGRA_DEBUG_UART_AUTO_ODMDATA)
auto_uart_id = auto_odmdata();
#elif defined(CONFIG_TEGRA_DEBUG_UART_AUTO_SCRATCH)
auto_uart_id = auto_scratch();
#else
auto_uart_id = -1;
#endif
if (auto_uart_id != -1)
uart_id = auto_uart_id;
if (uart_id < 0 || uart_id >= ARRAY_SIZE(uarts) ||
!uart_clocked(uart_id))
uart = NULL;
else
uart = (volatile u8 *)uarts[uart_id].base;
save_uart_address();
if (uart == NULL)
return;
chip = (apb_misc[0x804 / 4] >> 8) & 0xff;
if (chip == 0x20)
div = 0x0075;
else
div = 0x00dd;
uart[UART_LCR << DEBUG_UART_SHIFT] |= UART_LCR_DLAB;
uart[UART_DLL << DEBUG_UART_SHIFT] = div & 0xff;
uart[UART_DLM << DEBUG_UART_SHIFT] = div >> 8;
uart[UART_LCR << DEBUG_UART_SHIFT] = 3;
}
static inline void arch_decomp_wdog(void)
{
}
#endif