Messages in this thread | | | Date | Tue, 05 May 2015 12:02:10 +0100 | From | Daniel Thompson <> | Subject | Re: [PATCH] serial/amba-pl011: fix minor bugs for pio mode |
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On 05/05/15 04:00, Leo Yan wrote: > When use pio mode, there have two issues can be observed: > > - In the commit 2240197 "serial/amba-pl011: Leave the TX IRQ alone when > the UART is not open", it will skip clearing the TX IRQ across > pl011_shutdown() and pl011_startup(); So at the next time after the > uart port has been opened, there have chance for the function > pl011_tx_chars() will not be executed if the TX IRQ will not be > triggered; finally the console cannot output anymore. > > This is caused by the uart FIFO still keep data rather than > the threshold. So revert this patch to make sure every time open the > uart port, it will force to call function pl011_tx_chars(). > > - Sometimes will output the duplicate chars. Function pl011_tx_char() > will firstly send char and check if FIFO is full, and if the FIFO is > full it will return false; Caller function will consider the char > has _NOT_ been send out and resend it again, finally will send the > duplicate chars. So change to check FIFO is full or not, if full then > return false, otherwise send out char and return true.
I was going to comment that this patch should probably be split into two patches...
However whilst doing background reading I noticed that for both these issues there are existing patches to address them:
http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/334107.html
Do these fix the issues for you?
> > Signed-off-by: Leo Yan <leo.yan@linaro.org> > --- > drivers/tty/serial/amba-pl011.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c > index 5a4e9d5..9d9ac76 100644 > --- a/drivers/tty/serial/amba-pl011.c > +++ b/drivers/tty/serial/amba-pl011.c > @@ -1249,20 +1249,19 @@ __acquires(&uap->port.lock) > > /* > * Transmit a character > - * There must be at least one free entry in the TX FIFO to accept the char. > * > - * Returns true if the FIFO might have space in it afterwards; > - * returns false if the FIFO definitely became full. > + * Before send character, need check FIFO is full or not; > + * If FIFO is full, will not send char and return false, > + * otherwise send out character and return ture. > */ > static bool pl011_tx_char(struct uart_amba_port *uap, unsigned char c) > { > + if (readw(uap->port.membase + UART01x_FR) & UART01x_FR_TXFF) > + return false; > + > writew(c, uap->port.membase + UART01x_DR); > uap->port.icount.tx++; > - > - if (likely(uap->tx_irq_seen > 1)) > - return true; > - > - return !(readw(uap->port.membase + UART01x_FR) & UART01x_FR_TXFF); > + return true; > } > > static bool pl011_tx_chars(struct uart_amba_port *uap) > @@ -1639,6 +1638,9 @@ static int pl011_startup(struct uart_port *port) > > writew(uap->vendor->ifls, uap->port.membase + UART011_IFLS); > > + /* Assume that TX IRQ doesn't work until we see one: */ > + uap->tx_irq_seen = 0; > + > spin_lock_irq(&uap->port.lock); > > /* restore RTS and DTR */ > @@ -1702,7 +1704,7 @@ static void pl011_shutdown(struct uart_port *port) > spin_lock_irq(&uap->port.lock); > uap->im = 0; > writew(uap->im, uap->port.membase + UART011_IMSC); > - writew(0xffff & ~UART011_TXIS, uap->port.membase + UART011_ICR); > + writew(0xffff, uap->port.membase + UART011_ICR); > spin_unlock_irq(&uap->port.lock); > > pl011_dma_shutdown(uap); >
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