linux-kernel - Re: [PATCH 2/4] ARM: dts: da850: Add an aemif node

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Message-ID: <20160810094224.GH16481@gobelin>
Date:	Wed, 10 Aug 2016 09:42:24 +0000
From:	Karl Beldan <kbeldan@...libre.com>
To:	Sekhar Nori <nsekhar@...com>
Cc:	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Mark Rutland <mark.rutland@....com>,
	Karl Beldan <karl.beldan+oss@...il.com>,
	Kevin Hilman <khilman@...libre.com>,
	linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Santosh Shilimkar <ssantosh@...nel.org>
Subject: Re: [PATCH 2/4] ARM: dts: da850: Add an aemif node

On Wed, Aug 10, 2016 at 09:28:48AM +0000, Karl Beldan wrote:
> On Wed, Aug 10, 2016 at 02:04:48PM +0530, Sekhar Nori wrote:
> > On Wednesday 10 August 2016 02:04 PM, Karl Beldan wrote:
> > > On Wed, Aug 10, 2016 at 01:59:26PM +0530, Sekhar Nori wrote:
> > >> On Wednesday 10 August 2016 01:56 PM, Karl Beldan wrote:
> > >>> On Wed, Aug 10, 2016 at 01:42:01PM +0530, Sekhar Nori wrote:
> > >>>> On Wednesday 10 August 2016 01:37 PM, Karl Beldan wrote:
> > >>>>> On Wed, Aug 10, 2016 at 01:32:03PM +0530, Sekhar Nori wrote:
> > >>>>>> On Wednesday 10 August 2016 01:18 PM, Sekhar Nori wrote:
> > >>>>>>> On Tuesday 09 August 2016 10:45 PM, Karl Beldan wrote:
> > >>>>>>>> Currently the davinci da8xx boards use the mach-davinci aemif code.
> > >>>>>>>> Instantiating an aemif node into the DT allows to use the ti-aemif
> > >>>>>>>> memory driver and is another step to better DT support.
> > >>>>>>>> Also it will allow to properly pass the emif timings via DT.
> > >>>>>>>>
> > >>>>>>>> Signed-off-by: Karl Beldan <kbeldan@...libre.com>
> > >>>>>>>> ---
> > >>>>>>>>  arch/arm/boot/dts/da850.dtsi | 10 ++++++++++
> > >>>>>>>>  1 file changed, 10 insertions(+)
> > >>>>>>>>
> > >>>>>>>> diff --git a/arch/arm/boot/dts/da850.dtsi b/arch/arm/boot/dts/da850.dtsi
> > >>>>>>>> index bc10e7e..f62928c 100644
> > >>>>>>>> --- a/arch/arm/boot/dts/da850.dtsi
> > >>>>>>>> +++ b/arch/arm/boot/dts/da850.dtsi
> > >>>>>>>> @@ -411,6 +411,16 @@
> > >>>>>>>>  			dma-names = "tx", "rx";
> > >>>>>>>>  		};
> > >>>>>>>>  	};
> > >>>>>>>> +	aemif: aemif@...00000 {
> > >>>>>>>> +		compatible = "ti,da850-aemif";
> > >>>>>>>> +		#address-cells = <2>;
> > >>>>>>>> +		#size-cells = <1>;
> > >>>>>>>> +
> > >>>>>>>> +		reg = <0x68000000 0x00008000>;
> > >>>>>>>> +		ranges = <0 0 0x60000000 0x08000000
> > >>>>>>>> +			  1 0 0x68000000 0x00008000>;
> > >>>>>>>> +		status = "disabled";
> > >>>>>>>> +	};
> > >>>>>>>>  	nand_cs3@...00000 {
> > >>>>>>>>  		compatible = "ti,davinci-nand";
> > >>>>>>>>  		reg = <0x62000000 0x807ff
> > >>>>>>>
> > >>>>>>> The nand node should be part of aemif node like it is done for keystone
> > >>>>>>> boards.
> > >>>>>>
> > >>>>>> Actually, can you move the nand node out of da850.dtsi completely. Its
> > >>>>>> much better to keep da850.dtsi restricted to soc-internal devices and
> > >>>>>> keep the board level devices like NAND flash in <board>.dts file.
> > >>>>>>
> > >>>>>> Similarly, can you move the NAND pinmux definitions too to the
> > >>>>>> da850-evm.dts file?
> > >>>>>>
> > >>>>>> There is advantage in keeping common pinmux definitions in da850.dtsi so
> > >>>>>> each board doe not have to repeat them. But AEMIF is an exception as its
> > >>>>>> usage can really be varied (NAND, NOR, SRAM, other). Plus, different
> > >>>>>> boards are likely to use different chip selects so coming up with some
> > >>>>>> pinmux definitions which will be reused widely is really unlikely.
> > >>>>>>
> > >>>>> This is exactly what I just did for the LCDK.
> > >>>>> If everybody is happy with it I will do the same for the evm as I put it
> > >>>>> in the cover letter.
> > >>>>
> > >>>> Yes please. We dont want duplication of data between da850.dtsi and
> > >>>> da850-lcdk.dts files.
> > >>>>
> > >>> Then I'll wait for this series to be applied and then apply my changes
> > >>> to the EVM while retiring the nand_cs3 together.
> > >>
> > >> No, I prefer the fixup happens first. In the same series, you can first
> > >> fixup existing EVM and then add LCDK support.
> > >>
> > > 
> > > Well in that case you'll have to do the testing since I only have an
> > > LCDK. I should be able to send the series within the hour.
> > 
> > Sure. I can test it.
> > 
> The aemif/davinci_nand drivers don't configure AWCCR, yet davinci_nand
> relies on EM_WAIT for RDY/nBUSY, so for the moment I keep the default
> settings, but I configure the EM_WAIT pins in the pinctrl. I did it for
> the LCDK, and it is not done for the EVM. Since the EVM schematics are
> not public can you tell which EM_WAIT pins are connected ?
>  
Also the device name is nand_cs3 but the pin muxing also enables CS4
both in Linux and U-Boot, can you tell whether it is needed ?
Or maybe you can share the schematics and I'll check it myself ?
 
Karl