linux-kernel - Re: [PATCH v2 4/6] tty: serial: msm: Add TX DMA support

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Date:	Wed, 30 Sep 2015 14:29:19 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	"Ivan T. Ivanov" <ivan.ivanov@...aro.org>
Cc:	Andy Gross <agross@...eaurora.org>,
	David Brown <davidb@...eaurora.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	Frank Rowand <frank.rowand@...ymobile.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-soc@...r.kernel.org" <linux-soc@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v2 4/6] tty: serial: msm: Add TX DMA support

On Wed, Sep 30, 2015 at 01:08:24PM +0100, Ivan T. Ivanov wrote:
> Add transmit DMA support for UARTDM type of controllers.
> 
> Tested on APQ8064, which have UARTDM v1.3 and ADM DMA engine
> and APQ8016, which have UARTDM v1.4 and BAM DMA engine.
> 
> Signed-off-by: Ivan T. Ivanov <ivan.ivanov@...aro.org>
> ---
>  .../devicetree/bindings/serial/qcom,msm-uartdm.txt |   3 +
>  drivers/tty/serial/msm_serial.c                    | 312 +++++++++++++++++++--
>  drivers/tty/serial/msm_serial.h                    |   3 +
>  3 files changed, 294 insertions(+), 24 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/serial/qcom,msm-uartdm.txt b/Documentation/devicetree/bindings/serial/qcom,msm-uartdm.txt
> index a2114c217376..a600023d9ec1 100644
> --- a/Documentation/devicetree/bindings/serial/qcom,msm-uartdm.txt
> +++ b/Documentation/devicetree/bindings/serial/qcom,msm-uartdm.txt
> @@ -26,6 +26,9 @@ Required properties:
>  Optional properties:
>  - dmas: Should contain dma specifiers for transmit and receive channels
>  - dma-names: Should contain "tx" for transmit and "rx" for receive channels
> +- qcom,tx-crci: Identificator <u32> for Client Rate Control Interface to be
> +           used with TX DMA channel. Required when using DMA for transmission
> +           with UARTDM v1.3 and bellow.

This sounds like it belongs in the dma-specifier, and dealt with by the
DMA controller driver.

Why does the UART driver need to know about this?

Mark.
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