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Commit 5ec6960f authored by Dirk Brandewie's avatar Dirk Brandewie Committed by Thomas Gleixner
Browse files

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: default avatarDirk Brandewie <dirk.brandewie@gmail.com>
LKML-Reference: <1290436128-17958-1-git-send-email-dirk.brandewie@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 9cdca869

arch/x86/platform/ce4100/ce4100.c

+92 −2
Original line number Diff line number Diff line
@@ -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();

}



/*