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author | vikram pandita <vikram.pandita@ti.com> | 2009-12-11 16:16:37 -0800 |
---|---|---|
committer | Tony Lindgren <tony@atomide.com> | 2009-12-11 16:16:37 -0800 |
commit | ce13d4716a276f4331d78ba28a5093a63822ab95 (patch) | |
tree | 0537f1349cae8f963eea5c0da7d5cfa4e738149d | |
parent | ed32350dc5ccc2b00685d857c3270688d465cd41 (diff) | |
download | linux-ce13d4716a276f4331d78ba28a5093a63822ab95.tar.bz2 |
omap: serial: fix non-empty uart fifo read abort
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>
-rw-r--r-- | arch/arm/mach-omap2/serial.c | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c index 6278fe585c05..39b797bc14d6 100644 --- a/arch/arm/mach-omap2/serial.c +++ b/arch/arm/mach-omap2/serial.c @@ -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; } /** |