* Vikram Pandita <vikram.pandita@xxxxxx> [091203 15:27]: > 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: Cousson, Benoit <b-cousson@xxxxxx> > Signed-off-by: Vikram Pandita <vikram.pandita@xxxxxx> > --- > History of Patch: > V1: > http://patchwork.kernel.org/patch/61671/ > http://patchwork.kernel.org/patch/61672/ > > V2: Incorporate approach suggested by Tony L > Introduce IP version check in mach-omap2/serial.c file > > arch/arm/mach-omap2/serial.c | 29 +++++++++++++++++++++++++++++ > 1 files changed, 29 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c > index 2e17b57..bd646a2 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 > + * (OMAP1/2/3 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; > @@ -650,5 +668,16 @@ void __init omap_serial_init(void) > device_init_wakeup(dev, true); > DEV_CREATE_FILE(dev, &dev_attr_sleep_timeout); > } > + > +#ifdef CONFIG_ARCH_OMAP4 > + /* Never read empty UART fifo on omap4 */ > + p->serial_in = serial_in_override; > +#else > + /* OMAP2/3 */ > + /* Never read empty UART fifo on UARTs with IP rev >=0x52 */ > + 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; > +#endif > } > } We need to avoid ifdef else stuff, that just causes problems compiling in support for many omaps. In theory, we should be able to compile in support for all omaps starting with 16xx with v5 options.. Using cpu_is_omapxxxx() should do the trick here. Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
