linux-kernel - Re: [PATCH v2] ARM: PL011: Add support for Rx DMA buffer polling

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Message-ID: <CACRpkdaECZ5qtUVS=28eDyzLWvxx=mP6dWML5mYs9kwqnhEoJQ@mail.gmail.com>
Date:	Mon, 28 Jan 2013 09:28:42 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Chanho Min <chanho.min@....com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Alan Cox <alan@...ux.intel.com>, linux-kernel@...r.kernel.org,
	Pawel Moll <pawel.moll@....com>, linux-serial@...r.kernel.org,
	Chanho Min <chanho0207@...il.com>
Subject: Re: [PATCH v2] ARM: PL011: Add support for Rx DMA buffer polling

On Mon, Jan 28, 2013 at 9:15 AM, Chanho Min <chanho.min@....com> wrote:
> [Russell]
>>Well, I thought I had explained that I'd prefer to see the poll rate
>>adjusted with the baud rate, but maybe I wasn't explicit enough.
>>Instead, what we seem to have ended up with are two new entries in
>>platform data (which we're trying to get away from with DT):
>>
>>+       unsigned int dma_rx_poll_rate;
>>+       unsigned int dma_rx_poll_timeout;
>>
>>If this were to be done, then receive DMA could be used on the Versatile
>>PB platforms without having it suck CPU usage unnecessarily at slower
>>baud rates.
> This patch is working well on our pl011+ pl080 platform.
> If no data is received during time-out, no tick timer works.
> Do you want to adjust the poll rate with the baud rate additionally?

I'm not following, you wrote earlier in the thread:

>>Should we scale the polling interval according to baud
>>rate?
>
> It is also our concern, I will suggest the proper way.

We are waiting for you suggestion, i.e. a new patch iteration
taking this into account.

Yours,
Linus Walleij
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