Re: [PATCH] OMAP3: Serial: Improved sleep logic

Tony Lindgren
2010-02-04T16:10:03Z

* Tero.Kristo@nokia.com <Tero.Kristo@nokia.com> [100203 23:59]:
>
>
> >-----Original Message-----
> >From: ext Tony Lindgren [mailto:tony@atomide.com]
> >Sent: 03 February, 2010 19:50
> >To: Kristo Tero (Nokia-D/Tampere)
> >Cc: linux-omap@vger.kernel.org
> >Subject: Re: [PATCH] OMAP3: Serial: Improved sleep logic
> >
> >* Tero Kristo <tero.kristo@nokia.com> [100202 01:38]:
> >> From: Tero Kristo <tero.kristo@nokia.com>
> >>
> >> Only RX interrupt will now kick the sleep prevent timer. In
> >addition, TX
> >> fifo status is checked before disabling clocks, this will
> >prevent occasional
> >> garbage being printed on serial line. Smartidle is also
> >disabled while
> >> entering idle if we have data in the transmit buffer,
> >because having this
> >> enabled will prevent wakeups from the TX interrupt, and this causes
> >> pauses while sending large blocks of data.
> >
> >Sounds this is for 2.6.34 merge window and does not contain anything
> >that needs to be fixed for 2.6.33.
>
> Yeah, this only fixes a couple of annoying issues, but nothing fatal. Also improves power efficiency in some cases which is a nice to have feature, and basically eases the development of PM code as the UART does not block the system from sleeping always.

Yeah cool. Separate issue, but I wonder if we should also clear
the the first rx character from the fifo to avoid corrupting
the console. Only when the uart clocks are off and and
we get a key press. Would be easy to do just do with one
serial_read_reg(uart->p, UART_RX)..

Tony

>
> -Tero
>
> >
> >Regards,
> >
> >Tony
> >
> >
> >> Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
> >> ---
> >> arch/arm/mach-omap2/serial.c | 19 +++++++++++++++----
> >> 1 files changed, 15 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/arm/mach-omap2/serial.c
> >b/arch/arm/mach-omap2/serial.c
> >> index 777e802..e11dfe9 100644
> >> --- a/arch/arm/mach-omap2/serial.c
> >> +++ b/arch/arm/mach-omap2/serial.c
> >> @@ -317,7 +317,8 @@ static void omap_uart_allow_sleep(struct
> >omap_uart_state *uart)
> >> if (!uart->clocked)
> >> return;
> >>
> >> - omap_uart_smart_idle_enable(uart, 1);
> >> + if (serial_read_reg(uart->p, UART_LSR) & UART_LSR_TEMT)
> >> + omap_uart_smart_idle_enable(uart, 1);
> >> uart->can_sleep = 1;
> >> del_timer(&uart->timer);
> >> }
> >> @@ -335,7 +336,11 @@ void omap_uart_prepare_idle(int num)
> >>
> >> list_for_each_entry(uart, &uart_list, node) {
> >> if (num == uart->num && uart->can_sleep) {
> >> - omap_uart_disable_clocks(uart);
> >> + if (serial_read_reg(uart->p, UART_LSR) &
> >> + UART_LSR_TEMT)
> >> + omap_uart_disable_clocks(uart);
> >> + else
> >> + omap_uart_smart_idle_enable(uart, 0);
> >> return;
> >> }
> >> }
> >> @@ -407,8 +412,14 @@ int omap_uart_can_sleep(void)
> >> static irqreturn_t omap_uart_interrupt(int irq, void *dev_id)
> >> {
> >> struct omap_uart_state *uart = dev_id;
> >> + u8 lsr;
> >>
> >> - omap_uart_block_sleep(uart);
> >> + lsr = serial_read_reg(uart->p, UART_LSR);
> >> + /* Check for receive interrupt */
> >> + if (lsr & UART_LSR_DR)
> >> + omap_uart_block_sleep(uart);
> >> + if (lsr & UART_LSR_TEMT && uart->can_sleep)
> >> + omap_uart_smart_idle_enable(uart, 1);
> >>
> >> return IRQ_NONE;
> >> }
> >> --
> >> 1.5.4.3
> >>
> >> --
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