Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752674AbbF2NBf (ORCPT <rfc822;w@1wt.eu>);
	Mon, 29 Jun 2015 09:01:35 -0400
Received: from eusmtp01.atmel.com ([212.144.249.243]:43083 "EHLO
	eusmtp01.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752291AbbF2NBZ (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 29 Jun 2015 09:01:25 -0400
Message-ID: <55914164.1070800@atmel.com>
Date: Mon, 29 Jun 2015 15:00:20 +0200
From: Nicolas Ferre <nicolas.ferre@atmel.com>
Organization: atmel
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0
MIME-Version: 1.0
To: Cyrille Pitchen <cyrille.pitchen@atmel.com>, <gregkh@linuxfoundation.org>,
        <wenyou.yang@atmel.com>, <ludovic.desroches@atmel.com>,
        <leilei.zhao@atmel.com>, <josh.wu@atmel.com>,
        <alexandre.belloni@free-electrons.com>, <linux-serial@vger.kernel.org>
CC: <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
        <devicetree@vger.kernel.org>, <galak@codeaurora.org>,
        <ijc+devicetree@hellion.org.uk>, <mark.rutland@arm.com>,
        <pawel.moll@arm.com>, <robh+dt@kernel.org>
Subject: Re: [PATCH linux-next v2 1/4] ARM: at91/dt: add a new DT property
 to support FIFOs on Atmel USARTs
References: <cover.1434038494.git.cyrille.pitchen@atmel.com> <16bdcf0c3f710ca46df86eeea82c9840454cb7aa.1434038494.git.cyrille.pitchen@atmel.com>
In-Reply-To: <16bdcf0c3f710ca46df86eeea82c9840454cb7aa.1434038494.git.cyrille.pitchen@atmel.com>
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 8bit
X-Originating-IP: [10.161.30.18]
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2396
Lines: 58

Le 11/06/2015 18:20, Cyrille Pitchen a ?crit :
> This patch adds a new DT property, "atmel,fifo-size", to enable and set
> the maximum number of data the RX and TX FIFOs can store on FIFO capable
> USARTs.
> 
> Please be aware that the VERSION register can not be used to guess the
> size of FIFOs. Indeed, for a given hardware version, the USARTs can be
> integrated on Atmel SoCs with different FIFO sizes. Also the
> "atmel,fifo-size" property is optional as older USARTs don't embed FIFO at
> all.
> 
> Besides, the FIFO size can not be read or guessed from other registers:
> When designing the FIFO feature, no dedicated registers were added to
> store this size. Unsed spaces in the I/O register range are limited and
> better reserved for future usages. Instead, the FIFO size of each
> peripheral is documented in the programmer datasheet.
> 
> Finally, on a given SoC, there can be several instances of USART with
> different FIFO sizes. This explain why we'd rather use a dedicated DT
> property than use the "compatible" property.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>

Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

> ---
>  Documentation/devicetree/bindings/serial/atmel-usart.txt | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/atmel-usart.txt b/Documentation/devicetree/bindings/serial/atmel-usart.txt
> index 90787aa..e6e6142 100644
> --- a/Documentation/devicetree/bindings/serial/atmel-usart.txt
> +++ b/Documentation/devicetree/bindings/serial/atmel-usart.txt
> @@ -22,6 +22,8 @@ Optional properties:
>  		memory peripheral interface and USART DMA channel ID, FIFO configuration.
>  		Refer to dma.txt and atmel-dma.txt for details.
>  	- dma-names: "rx" for RX channel, "tx" for TX channel.
> +- atmel,fifo-size: maximum number of data the RX and TX FIFOs can store for FIFO
> +  capable USARTs.
>  
>  <chip> compatible description:
>  - at91rm9200:  legacy USART support
> @@ -57,4 +59,5 @@ Example:
>  		dmas = <&dma0 2 0x3>,
>  		       <&dma0 2 0x204>;
>  		dma-names = "tx", "rx";
> +		atmel,fifo-size = <32>;
>  	};
> 


-- 
Nicolas Ferre
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/