Tony, > -----Original Message----- > From: Tony Lindgren [mailto:[email protected]] > Sent: Tuesday, February 23, 2010 3:10 AM > To: Shilimkar, Santosh > Cc: [email protected]; [email protected]; > Woodruff, Richard; Ghorai, > Sukumar > Subject: Re: [PATCH 1/9] omap3/4: uart: fix full-fifo write abort > > * Shilimkar, Santosh <[email protected]> [100218 21:22]: > > Bye the way just to add bit more clarity, this patch addresses TX > > hardware restriction in the new UART IP used on omap3630 and omap4430. > > First part of the fix for RX is already in mainline, > > Commit: "ce13d4716a276f4331d78ba28a5093a63822ab95" > > > > More details on this thread are here. > > http://www.mail-archive.com/[email protected]/msg19447.html > > Thanks, I've updated the comments for this patch with the link above > and added the whole series into omap for-next. > Please drop this patch since it has introduces regression on interrupt latency while traces are enabled. Since 8250 driver calls serial_out() function is with interrupt disabled ( spin_lock_irqsave), the interrupt latency at times is as high as in few milliseconds because of error case.
I shall work towards this issue but for now we should drop this since the side effect of this change is known > > > > -----Original Message----- > > > From: Shilimkar, Santosh > > > Sent: Thursday, February 18, 2010 2:29 PM > > > To: [email protected] > > > Cc: [email protected]; [email protected]; > > > Shilimkar, Santosh; > Woodruff, > > > Richard; Ghorai, Sukumar > > > Subject: [PATCH 1/9] omap3/4: uart: fix full-fifo write abort > > > > > > This patch is addition to the already merged commit on non-empty > > > uart fifo read abort. "ce13d4716a276f4331d78ba28a5093a63822ab95" > > > > > > OMAP3630 and OMAP4430 UART IP blocks have a restriction on TX FIFO > > > too. If you try to write to the tx fifo when it is full, the system > > > aborts. > > > > > > This can be easily reproducible by not suppressing interconnect errors or > > > long duration testing where continuous prints over console from multiple > > > threads. This patch is addressing the issue by ensuring that write is > > > not issued while fifo is full. A timeout is added to avoid any hang > > > on fifo-full for 10 mS which is unlikely case. > > > > > > Patch is validated on OMAP3630 and OMAP4 SDP. > > > > > > V2 version removed the additional 1 uS on every TX as per > > > Tony's suggestion > > > > > > Signed-off-by: Woodruff Richard <[email protected]> > > > Signed-off-by: Santosh Shilimkar <[email protected]> > > > CC: Ghorai Sukumar <[email protected]> > > > --- > > > arch/arm/mach-omap2/serial.c | 31 ++++++++++++++++++++++++++++--- > > > 1 files changed, 28 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c > > > index 5f3035e..b79bc89 100644 > > > --- a/arch/arm/mach-omap2/serial.c > > > +++ b/arch/arm/mach-omap2/serial.c > > > @@ -23,6 +23,7 @@ > > > #include <linux/serial_reg.h> > > > #include <linux/clk.h> > > > #include <linux/io.h> > > > +#include <linux/delay.h> > > > > > > #include <plat/common.h> > > > #include <plat/board.h> > > > @@ -160,6 +161,13 @@ static inline unsigned int serial_read_reg(struct > > > plat_serial8250_port *up, > > > return (unsigned int)__raw_readb(up->membase + offset); > > > } > > > > > > +static inline void __serial_write_reg(struct uart_port *up, int offset, > > > + int value) > > > +{ > > > + offset <<= up->regshift; > > > + __raw_writeb(value, up->membase + offset); > > > +} > > > + > > > static inline void serial_write_reg(struct plat_serial8250_port *p, int > > > offset, > > > int value) > > > { > > > @@ -620,6 +628,20 @@ static unsigned int serial_in_override(struct > > > uart_port *up, int offset) > > > return __serial_read_reg(up, offset); > > > } > > > > > > +static void serial_out_override(struct uart_port *up, int offset, int > > > value) > > > +{ > > > + unsigned int status, tmout = 10000; > > > + > > > + status = __serial_read_reg(up, UART_LSR); > > > + while (!(status & UART_LSR_THRE)) { > > > + /* Wait up to 10ms for the character(s) to be sent. */ > > > + if (--tmout == 0) > > > + break; > > > + udelay(1); > > > + status = __serial_read_reg(up, UART_LSR); > > > + } > > > + __serial_write_reg(up, offset, value); > > > +} > > > void __init omap_serial_early_init(void) > > > { > > > int i; > > > @@ -721,11 +743,14 @@ void __init omap_serial_init_port(int port) > > > * omap3xxx: Never read empty UART fifo on UARTs > > > * with IP rev >=0x52 > > > */ > > > - if (cpu_is_omap44xx()) > > > + 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_out = serial_out_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; > > > + uart->p->serial_out = serial_out_override; > > > + } > > > } > > > > > > /** > > > -- > > > 1.6.0.4 > > Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
