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ce4100: Add errata fixes for UART on CE4100 

This patch enables the UART on the CE4100. The UART has a couple of
issues that need to be worked around. First the UART is mostly PC
compatible except that it is clocked eight times faster than a
standard PC so the default configuration provided in
arch/x86/include/asm/serial.h needs to be overridden. Second the TX
interrupt may not be set correctly all the time. Lastly accessing the
UART via I/O space for early_prink() hangs the chip when the IOAPIC is
enabled.

A custom mem_serial_in() is provided to work around the TX interrupt
issue. The configuration issues are dealt with in the call back
registered with the 8250 driver via serial8250_set_isa_configurator()

Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
LKML-Reference: <1290436128-17958-1-git-send-email-dirk.brandewie@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Dirk Brandewie 2010-11-22 06:28:48 -08:00 committed by Thomas Gleixner
parent 9cdca86972
commit 5ec6960f6f
1 changed files with 92 additions and 2 deletions
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94
arch/x86/platform/ce4100/ce4100.c
View File

@ -12,20 +12,110 @@
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/serial_reg.h>
#include <linux/serial_8250.h>
#include <asm/setup.h>
#include <asm/io.h>
static int ce4100_i8042_detect(void)
{
return 0;
}
static void __init sdv_arch_setup(void)
static void __init sdv_find_smp_config(void)
{
}
static void __init sdv_find_smp_config(void)
#ifdef CONFIG_SERIAL_8250
static unsigned int mem_serial_in(struct uart_port *p, int offset)
{
offset = offset << p->regshift;
return readl(p->membase + offset);
}
/*
* The UART Tx interrupts are not set under some conditions and therefore serial
* transmission hangs. This is a silicon issue and has not been root caused. The
* workaround for this silicon issue checks UART_LSR_THRE bit and UART_LSR_TEMT
* bit of LSR register in interrupt handler to see whether at least one of these
* two bits is set, if so then process the transmit request. If this workaround
* is not applied, then the serial transmission may hang. This workaround is for
* errata number 9 in Errata - B step.
*/
static unsigned int ce4100_mem_serial_in(struct uart_port *p, int offset)
{
unsigned int ret, ier, lsr;
if (offset == UART_IIR) {
offset = offset << p->regshift;
ret = readl(p->membase + offset);
if (ret & UART_IIR_NO_INT) {
/* see if the TX interrupt should have really set */
ier = mem_serial_in(p, UART_IER);
/* see if the UART's XMIT interrupt is enabled */
if (ier & UART_IER_THRI) {
lsr = mem_serial_in(p, UART_LSR);
/* now check to see if the UART should be
generating an interrupt (but isn't) */
if (lsr & (UART_LSR_THRE | UART_LSR_TEMT))
ret &= ~UART_IIR_NO_INT;
}
}
} else
ret = mem_serial_in(p, offset);
return ret;
}
static void ce4100_mem_serial_out(struct uart_port *p, int offset, int value)
{
offset = offset << p->regshift;
writel(value, p->membase + offset);
}
static void ce4100_serial_fixup(int port, struct uart_port *up,
unsigned short *capabilites)
{
#ifdef CONFIG_EARLY_PRINTK
/*
* Over ride the legacy port configuration that comes from
* asm/serial.h. Using the ioport driver then switching to the
* PCI memmaped driver hangs the IOAPIC
*/
if (up->iotype != UPIO_MEM32) {
up->uartclk = 14745600;
up->mapbase = 0xdffe0200;
set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
up->mapbase & PAGE_MASK);
up->membase =
(void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
up->membase += up->mapbase & ~PAGE_MASK;
up->iotype = UPIO_MEM32;
up->regshift = 2;
}
#endif
up->iobase = 0;
up->serial_in = ce4100_mem_serial_in;
up->serial_out = ce4100_mem_serial_out;
*capabilites |= (1 << 12);
}
static __init void sdv_serial_fixup(void)
{
serial8250_set_isa_configurator(ce4100_serial_fixup);
}
#else
static inline void sdv_serial_fixup(void);
#endif
static void __init sdv_arch_setup(void)
{
sdv_serial_fixup();
}
/*