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SubjectRe: [PATCH] serial/amba-pl011: fix minor bugs for pio mode
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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