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Subject[PATCH][RFC] AMD Elan patch
Hi,

the following patch for linux-2.4.17 fixes problems with the AMD Elan CPUs
which are popular x86 devices for embedded applications.

Content of the patch:
---------------------

1. add a new processor type "Elan" in "Processor type
and features", with CONFIG_MELAN, is introduced

2. fix the A20 code which was broken since the cleanup
in 2.4.17

3. correct the ioport resource registration for Elans
(standard kernel reserves ports which are special
function registers on Elans)

4. fix UART transmit bug

5. fix timer 0 frequency to correct the clock

Details:
--------

1. As discussed on LKML the Elan processors have some
"features" which need to be fixed but should not live
in a standard kernel. Therefore, we propose a new
configuration option CONFIG_MELAN. Ideas for better
places for this option in the configuration tree are
welcome.

2. In 2.4.15 H. Peter Anvin ported the A20 gate code from
syslinux to the kernel, which is much more sophisticated
than the code we had before. This leads to the Elan
processors not booting any more (they did before without
any problem, but that was more luck than intention). If
you try to boot kernels newer than 2.4.14 the system
reboots right in the middle of the initialisation
sequence. As the Elans don't have a keyboard controller
a special A20 gate sequence is added according to the
config option introduced in 1.

3. Due to the fact that the ports of the PIC of the original
PC are mirrored to several adresses Linux normally reserves
the areas 0x20..0x3f and 0xa0..0xbf for pic1 and pic2,
although the PICs use only the first two adresses of each
block. This part of the patch uses only the "real" adresses,
(0x20,0x21 / 0xa0,0xa1) as the Elan processors have special
function registers in these blocks for the integrated
peripherals.

4. The on-chip serial interface has a bug: the UART_LSR_THRE
bit is delayed one bit clock after the interrupt line is
asserted, i.e. if the serial port is running at 1200 bps, and
the tranmitter becomes empty and causes an interupt, the
interrupt is signalled about a millisecond (1/1200second)
_before_ the THRE bit is set. This means that when the
interrupt handler is entered after the interrupt, the THRE
bit is still clear, the handler believes that there is
nothing to be done and returns.

5. A normal PC has a basic frequency for the system timer 0
of 1.19318 MHz, whereas the Elans have 1.1892 MHz due to the
fact that all clocks are derived from a single oscillator.
Without the patch the clock is wrong.

Credits:
--------

- Anders Larsen <anders@alarsen.net>
First attempt of a patch for the Elan series
http://www.uwsg.iu.edu/hypermail/linux/kernel/0004.2/0667.html

- Jason Sodergren <jason@mugwump.taiga.com>
Clock patch

- Christer Weinigel <wingel@hog.ctrl-c.liu.se>
Serial interface patch, A20 patch

- H. Peter Anvin <hpa@zytor.com>
Discussions and ideas about the A20 stuff

Patch:
------

The latest version of this patch can always be found on

http://www.pengutronix.de/software/elan_en.html

The following code is version 2.4.17.2 of the patch. Suggestions for
further improvement are welcome.

----------8<----------8<----------8<----------8<----------8<----------
diff -urN -X kernel-patches/dontdiff linux-2.4.17/Documentation/Configure.help linux-2.4.17-rs/Documentation/Configure.help
--- linux-2.4.17/Documentation/Configure.help Fri Dec 21 18:41:53 2001
+++ linux-2.4.17-rs/Documentation/Configure.help Mon Dec 31 17:12:58 2001
@@ -3813,6 +3813,7 @@
- "Pentium-4" for the Intel Pentium 4.
- "K6" for the AMD K6, K6-II and K6-III (aka K6-3D).
- "Athlon" for the AMD K7 family (Athlon/Duron/Thunderbird).
+ - "Elan" for the AMD Elan family (Elan SC400/SC410).
- "Crusoe" for the Transmeta Crusoe series.
- "Winchip-C6" for original IDT Winchip.
- "Winchip-2" for IDT Winchip 2.
diff -urN -X kernel-patches/dontdiff linux-2.4.17/arch/i386/boot/setup.S linux-2.4.17-rs/arch/i386/boot/setup.S
--- linux-2.4.17/arch/i386/boot/setup.S Fri Nov 9 22:58:02 2001
+++ linux-2.4.17-rs/arch/i386/boot/setup.S Mon Dec 31 17:20:17 2001
@@ -42,6 +42,9 @@
* if CX/DX have been changed in the e801 call and if so use AX/BX .
* Michael Miller, April 2001 <michaelm@mjmm.org>
*
+ * New A20 code ported from SYSLINUX by H. Peter Anvin. AMD Elan bugfixes
+ * by Robert Schwebel, December 2001 <robert@schwebel.de>
+ *
*/

#include <linux/config.h>
@@ -646,7 +649,14 @@
#
# Enable A20. This is at the very best an annoying procedure.
# A20 code ported from SYSLINUX 1.52-1.63 by H. Peter Anvin.
+# AMD Elan bug fix by Robert Schwebel.
#
+
+#if defined(CONFIG_MELAN)
+ inb $0xee, %al # reading 0xee enables A20
+ jmp a20_done
+#endif
+

A20_TEST_LOOPS = 32 # Iterations per wait
A20_ENABLE_LOOPS = 255 # Total loops to try
diff -urN -X kernel-patches/dontdiff linux-2.4.17/arch/i386/config.in linux-2.4.17-rs/arch/i386/config.in
--- linux-2.4.17/arch/i386/config.in Fri Dec 21 18:41:53 2001
+++ linux-2.4.17-rs/arch/i386/config.in Mon Dec 31 15:22:06 2001
@@ -37,6 +37,7 @@
Pentium-4 CONFIG_MPENTIUM4 \
K6/K6-II/K6-III CONFIG_MK6 \
Athlon/Duron/K7 CONFIG_MK7 \
+ Elan CONFIG_MELAN \
Crusoe CONFIG_MCRUSOE \
Winchip-C6 CONFIG_MWINCHIPC6 \
Winchip-2 CONFIG_MWINCHIP2 \
@@ -125,6 +126,11 @@
define_bool CONFIG_X86_USE_3DNOW y
define_bool CONFIG_X86_PGE y
define_bool CONFIG_X86_USE_PPRO_CHECKSUM y
+fi
+if [ "$CONFIG_MELAN" = "y" ]; then
+ define_int CONFIG_X86_L1_CACHE_SHIFT 4
+ define_bool CONFIG_X86_USE_STRING_486 y
+ define_bool CONFIG_X86_ALIGNMENT_16 y
fi
if [ "$CONFIG_MCYRIXIII" = "y" ]; then
define_int CONFIG_X86_L1_CACHE_SHIFT 5
diff -urN -X kernel-patches/dontdiff linux-2.4.17/arch/i386/kernel/setup.c linux-2.4.17-rs/arch/i386/kernel/setup.c
--- linux-2.4.17/arch/i386/kernel/setup.c Fri Dec 21 18:41:53 2001
+++ linux-2.4.17-rs/arch/i386/kernel/setup.c Mon Dec 31 18:46:15 2001
@@ -329,6 +329,10 @@
{ "dma2", 0xc0, 0xdf, IORESOURCE_BUSY },
{ "fpu", 0xf0, 0xff, IORESOURCE_BUSY }
};
+#ifdef CONFIG_ELAN
+standard_io_resources[1] = { "pic1", 0x20, 0x21, IORESOURCE_BUSY };
+standard_io_resources[5] = { "pic2", 0xa0, 0xa1, IORESOURCE_BUSY };
+#endif

#define STANDARD_IO_RESOURCES (sizeof(standard_io_resources)/sizeof(struct resource))

diff -urN -X kernel-patches/dontdiff linux-2.4.17/drivers/char/serial.c linux-2.4.17-rs/drivers/char/serial.c
--- linux-2.4.17/drivers/char/serial.c Fri Dec 21 18:41:54 2001
+++ linux-2.4.17-rs/drivers/char/serial.c Mon Dec 31 17:53:45 2001
@@ -57,6 +57,9 @@
* 10/00: add in optional software flow control for serial console.
* Kanoj Sarcar <kanoj@sgi.com> (Modified by Theodore Ts'o)
*
+ * 12/01: Fix for AMD Elan bug in transmit irq routine, by
+ * Christer Weinigel <wingel@hog.ctrl-c.liu.se>,
+ * Robert Schwebel <robert@schwebel.de>
*/

static char *serial_version = "5.05c";
@@ -853,7 +856,7 @@
if (!info) {
info = IRQ_ports[irq];
if (pass_counter++ > RS_ISR_PASS_LIMIT) {
-#if 0
+#ifdef SERIAL_DEBUG_INTR
printk("rs loop break\n");
#endif
break; /* Prevent infinite loops */
@@ -886,6 +889,9 @@
int first_multi = 0;
struct rs_multiport_struct *multi;
#endif
+#ifdef CONFIG_MELAN
+ int iir;
+#endif

#ifdef SERIAL_DEBUG_INTR
printk("rs_interrupt_single(%d)...", irq);
@@ -900,7 +906,9 @@
if (multi->port_monitor)
first_multi = inb(multi->port_monitor);
#endif
-
+#ifdef CONFIG_MELAN
+ iir = serial_in(info, UART_IIR);
+#endif
do {
status = serial_inp(info, UART_LSR);
#ifdef SERIAL_DEBUG_INTR
@@ -909,10 +917,24 @@
if (status & UART_LSR_DR)
receive_chars(info, &status, regs);
check_modem_status(info);
+
+#ifdef CONFIG_M_ELAN
+ /*
+ * There is a bug in the UART on the AMD Elan SC4x0
+ * embedded processor series; the THRE bit of the line
+ * status register seems to be delayed one bit clock after
+ * the interrupt is generated, so kludge this if the
+ * IIR indicates a Transmit Holding Register Interrupt
+ *
+ */
+ if (status & UART_LSR_THRE || (iir & UART_IIR_ID) == UART_IIR_THRI)
+ transmit_chars(info, 0);
+#else
if (status & UART_LSR_THRE)
transmit_chars(info, 0);
+#endif
if (pass_counter++ > RS_ISR_PASS_LIMIT) {
-#if 0
+#ifdef SERIAL_DEBUG_INTR
printk("rs_single loop break.\n");
#endif
break;
diff -urN -X kernel-patches/dontdiff linux-2.4.17/include/asm-i386/timex.h linux-2.4.17-rs/include/asm-i386/timex.h
--- linux-2.4.17/include/asm-i386/timex.h Thu Nov 22 20:46:18 2001
+++ linux-2.4.17-rs/include/asm-i386/timex.h Mon Dec 31 16:08:55 2001
@@ -9,7 +9,12 @@
#include <linux/config.h>
#include <asm/msr.h>

-#define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
+#ifdef CONFIG_MELAN
+# define CLOCK_TICK_RATE 1189200 /* AMD Elan has different frequency! */
+#else
+# define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
+#endif
+
#define CLOCK_TICK_FACTOR 20 /* Factor of both 1000000 and CLOCK_TICK_RATE */
#define FINETUNE ((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) * \
(1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR)) \
----------8<----------8<----------8<----------8<----------8<----------
Robert
--
+--------------------------------------------------------+
| Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de |
| Pengutronix - Linux Solutions for Science and Industry |
| Braunschweiger Str. 79, 31134 Hildesheim, Germany |
| Phone: +49-5121-28619-0 | Fax: +49-5121-28619-4 |
+--------------------------------------------------------+









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