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

[Kevin Hilman <khilman@deeprootsystems.com>]

Tero Kristo <tero.kristo@nokia.com> writes:

> 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.
>
> Signed-off-by: Tero Kristo <tero.kristo@nokia.com>

After doing some more testing with this, something is not quite right
still.  I haven't taken the time to debug further, but with this patch
on top of the current PM branch, the timer seems to expire and disable
clocks whether or not there is UART activity.

In particular, using a UART1 console on OMAP3EVM, I notice that while
typing longer commands (that take more that <timeout> seconds to type),
I notice that I loose chars in the middle of typing.  /me doesn't like.

So I won't be applying this to the PM branch until we can figure out
what's happening here.

Kevin

> ---
>  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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