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Date: Fri, 9 Mar 2018 09:37:38 +0100
From: Lothar =?UTF-8?B?V2HDn21hbm4=?= <LW@KARO-electronics.de>
To: Martin Kaiser <martin@kaiser.cx>
Cc: Shawn Guo <shawnguo@kernel.org>, Sascha Hauer <kernel@pengutronix.de>,
        Fabio Estevam <fabio.estevam@nxp.com>,
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        Russell King <linux@armlinux.org.uk>,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ARM: dts: i.MX25: define SSI FIFO depth
Message-ID: <20180309093738.7cd5fded@karo-electronics.de>
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        <20180308153832.GA28454@botnar.kaiser.cx>
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Hi,

On Thu, 8 Mar 2018 16:38:32 +0100 Martin Kaiser wrote:
> Hi Lothar,
> 
> Thus wrote Lothar Waßmann (LW@KARO-electronics.de):
> 
> > > diff --git a/arch/arm/boot/dts/imx25.dtsi b/arch/arm/boot/dts/imx25.dtsi
> > > index 9725705..cf70df2 100644
> > > --- a/arch/arm/boot/dts/imx25.dtsi
> > > +++ b/arch/arm/boot/dts/imx25.dtsi
> > > @@ -269,6 +269,7 @@
> > >  				dmas = <&sdma 24 1 0>,
> > >  				       <&sdma 25 1 0>;
> > >  				dma-names = "rx", "tx";
> > > +				fsl,fifo-depth = <15>;
> > >  				status = "disabled";
> > >  			};
> 
> > > @@ -329,6 +330,7 @@
> > >  				dmas = <&sdma 28 1 0>,
> > >  				       <&sdma 29 1 0>;
> > >  				dma-names = "rx", "tx";
> > > +				fsl,fifo-depth = <15>;
> > >  				status = "disabled";
> > >  			};
> 
> > You are changing the global .dtsi file. Did you test this change with
> > all devices that are affected by it?
> 
> I changed the hardware description of the imx25 SSI to match the
> reference manual.
> 
> I did test this change on an imx25 board with audio playback. This uses
> the SSI description I modified. I verified that the driver is actually
> taking the modified setting into account and that this causes no
> problems.
> 
> As of today, this setting is used by the fsl_ssi driver to set the fifo
> water level for dma requests.
> 
> Of course, I don't have access to the enitre range of supported imx25
> boards and I don't think this is required for submitting patches.
> 
> Do you have any indication why this patch should not be merged?
> 
Usually patches should not willy-nilly change the behaviour of existing
configurations unless they fix any real life bugs.


Lothar Waßmann