[coreboot-gerrit] Patch set updated for coreboot: f0e23d4 uart8250: Fix and unify baudrate divisor calculation
Kyösti Mälkki (kyosti.malkki@gmail.com)
gerrit at coreboot.org
Mon Feb 24 10:34:35 CET 2014
Kyösti Mälkki (kyosti.malkki at gmail.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/5229
-gerrit
commit f0e23d43d1a0d4c9e80f58b2efbfe84a32228e3f
Author: Kyösti Mälkki <kyosti.malkki at gmail.com>
Date: Mon Feb 17 19:37:52 2014 +0200
uart8250: Fix and unify baudrate divisor calculation
Divisor is a function of requested baudrate, platform-specific
reference clock and amount of oversampling done on the UART reference.
Calculate this parameter with divisor rounded to nearest integer.
When building without option_table or when there is no entry for
baud_rate, CONFIG_TTYS0_BAUD is used for default baudrate.
For OxPCIe use of 4 MHz for reference was arbitrary giving correct
divisor for 115200 but somewhat inaccurate for lower baudrates.
Actual hardware is 62500000 with 16 times oversampling.
FIXME: Field for baudrate in lb_tables is still incorrect.
Change-Id: I68539738469af780fadd3392263dd9b3d5964d2d
Signed-off-by: Kyösti Mälkki <kyosti.malkki at gmail.com>
---
src/arch/x86/lib/romcc_console.c | 1 +
src/drivers/oxford/oxpcie/oxpcie_early.c | 10 ++++++-
src/drivers/uart/Makefile.inc | 6 ++++
src/drivers/uart/util.c | 48 ++++++++++++++++++++++++++++++++
src/include/uart.h | 17 +++++++++++
src/include/uart8250.h | 4 ---
src/lib/uart8250.c | 35 ++++++-----------------
src/lib/uart8250mem.c | 24 +---------------
8 files changed, 91 insertions(+), 54 deletions(-)
diff --git a/src/arch/x86/lib/romcc_console.c b/src/arch/x86/lib/romcc_console.c
index db84f9e..c5e6882 100644
--- a/src/arch/x86/lib/romcc_console.c
+++ b/src/arch/x86/lib/romcc_console.c
@@ -32,6 +32,7 @@
#endif
#if CONFIG_CONSOLE_SERIAL8250
+#include "drivers/uart/util.c"
#include "lib/uart8250.c"
#endif
#if CONFIG_CONSOLE_NE2K
diff --git a/src/drivers/oxford/oxpcie/oxpcie_early.c b/src/drivers/oxford/oxpcie/oxpcie_early.c
index d04e9d4..4f6f964 100644
--- a/src/drivers/oxford/oxpcie/oxpcie_early.c
+++ b/src/drivers/oxford/oxpcie/oxpcie_early.c
@@ -21,6 +21,7 @@
#include <arch/io.h>
#include <arch/early_variables.h>
#include <delay.h>
+#include <uart.h>
#include <uart8250.h>
#include <device/pci_def.h>
@@ -116,7 +117,14 @@ void oxford_init(void)
/* Now the UART initialization */
u32 uart0_base = CONFIG_OXFORD_OXPCIE_BASE_ADDRESS + 0x1000;
- uart8250_mem_init(uart0_base, (4000000 / CONFIG_TTYS0_BAUD));
+ unsigned int div = uart_baudrate_divisor(default_baudrate(),
+ uart_platform_refclk(), 16);
+ uart8250_mem_init(uart0_base, div);
}
#endif
+
+unsigned int uart_platform_refclk(void)
+{
+ return 62500000;
+}
diff --git a/src/drivers/uart/Makefile.inc b/src/drivers/uart/Makefile.inc
new file mode 100644
index 0000000..c797d4b
--- /dev/null
+++ b/src/drivers/uart/Makefile.inc
@@ -0,0 +1,6 @@
+ifeq ($(CONFIG_CONSOLE_SERIAL),y)
+romstage-y += util.c
+ramstage-y += util.c
+bootblock-y += util.c
+smm-y += util.c
+endif
diff --git a/src/drivers/uart/util.c b/src/drivers/uart/util.c
new file mode 100644
index 0000000..c577048
--- /dev/null
+++ b/src/drivers/uart/util.c
@@ -0,0 +1,48 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * 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; version 2 of the License.
+ *
+ * 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 St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <console/console.h>
+#include <uart.h>
+#if CONFIG_USE_OPTION_TABLE
+#include <pc80/mc146818rtc.h>
+#include "option_table.h"
+#endif
+
+unsigned int default_baudrate(void)
+{
+#if !defined(__SMM__) && CONFIG_USE_OPTION_TABLE
+ static const unsigned baud[8] =
+ { 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200 };
+ unsigned b_index = 0;
+#if defined(__PRE_RAM__)
+ b_index = read_option(baud_rate, 0xff);
+#else
+ if (get_option(&b_index, "baud_rate") != CB_SUCCESS)
+ b_index = 0xff;
+#endif
+ if (b_index < 8)
+ return baud[b_index];
+#endif
+ return CONFIG_TTYS0_BAUD;
+}
+
+/* Calculate divisor. Do not floor but round to nearest integer. */
+unsigned int uart_baudrate_divisor(unsigned int baudrate,
+ unsigned int refclk, unsigned int oversample)
+{
+ return (1 + (2 * refclk) / (baudrate * oversample)) / 2;
+}
diff --git a/src/include/uart.h b/src/include/uart.h
index b520e09..997fe18 100644
--- a/src/include/uart.h
+++ b/src/include/uart.h
@@ -20,6 +20,23 @@
#ifndef UART_H
#define UART_H
+/* Return the clock frequency UART uses as reference clock for
+ * baudrate generator. */
+unsigned int uart_platform_refclk(void);
+
+/* Return the baudrate determined from option_table, or when that is
+ * not used, CONFIG_TTYS0_BAUD.
+ */
+unsigned int default_baudrate(void);
+
+/* Returns the divisor value for a given baudrate.
+ * The formula to satisfy is:
+ * refclk / divisor = baudrate * oversample
+ */
+unsigned int uart_baudrate_divisor(unsigned int baudrate,
+ unsigned int refclk, unsigned int oversample);
+
+
unsigned char uart_rx_byte(void);
void uart_tx_byte(unsigned char data);
void uart_tx_flush(void);
diff --git a/src/include/uart8250.h b/src/include/uart8250.h
index a48c948..112cd44 100644
--- a/src/include/uart8250.h
+++ b/src/include/uart8250.h
@@ -105,10 +105,6 @@
#define UART_SCR 0x07
#define UART_SPR 0x07
-#if ((115200 % CONFIG_TTYS0_BAUD) != 0)
-#error Bad ttyS0 baud rate
-#endif
-
#if CONFIG_CONSOLE_SERIAL8250
unsigned char uart8250_rx_byte(unsigned base_port);
int uart8250_can_rx_byte(unsigned base_port);
diff --git a/src/lib/uart8250.c b/src/lib/uart8250.c
index c9075a2..d136eb8 100644
--- a/src/lib/uart8250.c
+++ b/src/lib/uart8250.c
@@ -21,15 +21,16 @@
#include <arch/io.h>
#include <uart.h>
#include <uart8250.h>
-#include <pc80/mc146818rtc.h>
#include <trace.h>
-#if CONFIG_USE_OPTION_TABLE
-#include "option_table.h"
-#endif
-
/* Should support 8250, 16450, 16550, 16550A type UARTs */
+/* Nominal values only, good for the range of choices Kconfig offers for
+ * set of standard baudrates.
+ */
+#define BAUDRATE_REFCLK (115200)
+#define BAUDRATE_OVERSAMPLE (1)
+
/* Expected character delay at 1200bps is 9ms for a working UART
* and no flow-control. Assume UART as stuck if shift register
* or FIFO takes more than 50ms per character to appear empty.
@@ -108,26 +109,8 @@ void uart8250_init(unsigned base_port, unsigned divisor)
void uart_init(void)
{
- /* TODO the divisor calculation is hard coded to standard UARTs. Some
- * UARTs won't work with these values. This should be a property of the
- * UART used, worst case a Kconfig variable. For now live with hard
- * codes as the only devices that might be different are the iWave
- * iRainbowG6 and the OXPCIe952 card (and the latter is memory mapped)
- */
- unsigned int div = (115200 / CONFIG_TTYS0_BAUD);
-
-#if !defined(__SMM__) && CONFIG_USE_OPTION_TABLE
- static const unsigned char divisor[8] = { 1, 2, 3, 6, 12, 24, 48, 96 };
- unsigned b_index = 0;
-#if defined(__PRE_RAM__)
- b_index = read_option(baud_rate, 0);
- b_index &= 7;
- div = divisor[b_index];
-#else
- if (get_option(&b_index, "baud_rate") == CB_SUCCESS)
- div = divisor[b_index];
-#endif
-#endif
-
+ unsigned int div;
+ div = uart_baudrate_divisor(default_baudrate(), BAUDRATE_REFCLK,
+ BAUDRATE_OVERSAMPLE);
uart8250_init(CONFIG_TTYS0_BASE, div);
}
diff --git a/src/lib/uart8250mem.c b/src/lib/uart8250mem.c
index 040e732..5e96825 100644
--- a/src/lib/uart8250mem.c
+++ b/src/lib/uart8250mem.c
@@ -21,10 +21,6 @@
#include <arch/io.h>
#include <uart.h>
#include <uart8250.h>
-#include <pc80/mc146818rtc.h>
-#if CONFIG_USE_OPTION_TABLE
-#include "option_table.h"
-#endif
#include <device/device.h>
#include <delay.h>
@@ -96,7 +92,6 @@ void uart8250_mem_init(unsigned base_port, unsigned divisor)
/* DLAB on */
write8(base_port + UART_LCR, UART_LCR_DLAB | CONFIG_TTYS0_LCS);
- /* Set Baud Rate Divisor. 12 ==> 9600 Baud */
write8(base_port + UART_DLL, divisor & 0xFF);
write8(base_port + UART_DLM, (divisor >> 8) & 0xFF);
@@ -106,27 +101,11 @@ void uart8250_mem_init(unsigned base_port, unsigned divisor)
u32 uart_mem_init(void)
{
- unsigned uart_baud = CONFIG_TTYS0_BAUD;
u32 uart_bar = 0;
unsigned div;
- /* find out the correct baud rate */
-#if !defined(__SMM__) && CONFIG_USE_OPTION_TABLE
- static const unsigned baud[8] = { 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200 };
- unsigned b_index = 0;
-#if defined(__PRE_RAM__)
- b_index = read_option(baud_rate, 0);
- b_index &= 7;
- uart_baud = baud[b_index];
-#else
- if (get_option(&b_index, "baud_rate") == CB_SUCCESS)
- uart_baud = baud[b_index];
-#endif
-#endif
-
/* Now find the UART base address and calculate the divisor */
#if CONFIG_DRIVERS_OXFORD_OXPCIE
-
#if defined(MORE_TESTING) && !defined(__SIMPLE_DEVICE__)
device_t dev = dev_find_device(0x1415, 0xc158, NULL);
if (!dev)
@@ -145,10 +124,9 @@ u32 uart_mem_init(void)
#endif
uart_bar = CONFIG_OXFORD_OXPCIE_BASE_ADDRESS + 0x1000; // 1st UART
// uart_bar = CONFIG_OXFORD_OXPCIE_BASE_ADDRESS + 0x2000; // 2nd UART
-
- div = 4000000 / uart_baud;
#endif
+ div = uart_baudrate_divisor(default_baudrate(), uart_platform_refclk(), 16);
if (uart_bar)
uart8250_mem_init(uart_bar, div);
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