linux-kernel - Re: [PATCH linux-next v2 3/4] tty/serial: at91: add support to FIFOs

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Message-ID: <20150618163636.GP27492@piout.net>
Date:	Thu, 18 Jun 2015 18:36:36 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Cyrille Pitchen <cyrille.pitchen@...el.com>
Cc:	nicolas.ferre@...el.com, gregkh@...uxfoundation.org,
	wenyou.yang@...el.com, ludovic.desroches@...el.com,
	leilei.zhao@...el.com, josh.wu@...el.com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	galak@...eaurora.org, ijc+devicetree@...lion.org.uk,
	mark.rutland@....com, pawel.moll@....com, robh+dt@...nel.org
Subject: Re: [PATCH linux-next v2 3/4] tty/serial: at91: add support to FIFOs

Hi,

On 11/06/2015 at 18:20:16 +0200, Cyrille Pitchen wrote :
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...el.com>

Seems good to me, a few comments:

> +	if (port->fifo_size < 8 || port->fifo_size > 32) {

I'm not sure why you limit the size to 32. At some point, a new SoC may
be release with a bigger FIFO then we'll have to change the code instead
of just putting the appropriate value in the device tree.

> +		port->fifo_size = 0;
> +		dev_err(&pdev->dev, "Invalid FIFO size\n");
> +		return;
> +	}
> +
> +	/*
> +	 * 0 <= rts_low <= rts_high <= fifo_size
> +	 * Once their CTS line asserted by the remote peer, some x86 UARTs tend
> +	 * to flush their internal TX FIFO, commonly up to 8 data, before
> +	 * actually stopping to send new data. So we try to set the RTS High
> +	 * Threshold to a raisonable high value respecting this 8 data empirical
              reasonably --^

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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