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omap: serial: fix non-empty uart fifo read abort

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OMAP3xxx and OMAP4430 UART IP blocks have a restriction wrt RX FIFO.
Empty RX fifo read causes an abort.

OMAP3xxx:
	UART IP revision >= 0x52 have this issue
	MVR register format is:
	Bits  Field Name  Description  				Type  Reset
	31:8   RESERVED 					RO  	0x0
	7:4    MAJOR  	Major revision number of the module.  	RO  	0x--
	3:0    MINOR  	Minor revision number of the module.  	RO  	0x--

OMAP4xxx:
	All revisions have this issue
	Revision id check is not used as the format of MVR resigster has changed
	For omap4 MVR register reads as: 0x50410602 => Revision id = 0x0602
	Format of MVR register on omap4 is: (Courtesy: Cousson, Benoit)
	Bits  Field Name  Description  				Type  Reset
	31:30 SCHEME  	Scheme revision number of module  	RO  	0x1
	29:28 RESERVED   					RO  	0x1
	27:16 FUNC  	Function revision number of module  	RO  	0x041
	15:11 RTL  		Rtl revision number of module  	RO  	0x00
	10:8  MAJOR 	Major revision number of the module.  	RO  	0x6
	7:6   CUSTOM  	Custom revision number of the module.  	RO  	0x0
	5:0   MINOR  	Minor revision number of the module.  	RO  	0x02

Override the default 8250 read handler: mem_serial_in()
by a custom handler: serial_in_8250()
which makes sure that RX fifo is not read when empty

tested on zoom3(3630) board

Cc: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This commit is contained in:
vikram pandita 2009-12-11 16:16:37 -08:00 committed by Tony Lindgren
parent ed32350dc5
commit ce13d4716a
1 changed files with 27 additions and 9 deletions
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36
arch/arm/mach-omap2/serial.c
View File

@ -33,6 +33,7 @@
#include "pm.h"
#include "prm-regbits-34xx.h"
#define UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV 0x52
#define UART_OMAP_WER 0x17 /* Wake-up enable register */
#define DEFAULT_TIMEOUT (5 * HZ)
@ -572,6 +573,23 @@ static struct omap_uart_state omap_uart[] = {
#endif
};
/*
* Override the default 8250 read handler: mem_serial_in()
* Empty RX fifo read causes an abort on omap3630 and omap4
* This function makes sure that an empty rx fifo is not read on these silicons
* (OMAP1/2/3430 are not affected)
*/
static unsigned int serial_in_override(struct uart_port *up, int offset)
{
if (UART_RX == offset) {
unsigned int lsr;
lsr = serial_read_reg(omap_uart[up->line].p, UART_LSR);
if (!(lsr & UART_LSR_DR))
return -EPERM;
}
return serial_read_reg(omap_uart[up->line].p, offset);
}
void __init omap_serial_early_init(void)
{
int i;
@ -667,15 +685,15 @@ void __init omap_serial_init_port(int port)
DEV_CREATE_FILE(dev, &dev_attr_sleep_timeout);
}
/* omap44xx: Never read empty UART fifo
* omap3xxx: Never read empty UART fifo on UARTs
* with IP rev >=0x52
*/
if (cpu_is_omap44xx())
uart->p->serial_in = serial_in_override;
else if ((serial_read_reg(uart->p, UART_OMAP_MVER) & 0xFF)
>= UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV)
uart->p->serial_in = serial_in_override;
/* omap44xx: Never read empty UART fifo
* omap3xxx: Never read empty UART fifo on UARTs
* with IP rev >=0x52
*/
if (cpu_is_omap44xx())
uart->p->serial_in = serial_in_override;
else if ((serial_read_reg(uart->p, UART_OMAP_MVER) & 0xFF)
>= UART_OMAP_NO_EMPTY_FIFO_READ_IP_REV)
uart->p->serial_in = serial_in_override;
}
/**