Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma

[Eugen Hristev]

On 29.05.2018 10:10, Peter Rosin wrote:
> On 2018-05-29 08:30, Eugen Hristev wrote:
> > On 28.05.2018 13:10, Peter Rosin wrote:
> > > On 2018-05-28 00:11, Peter Rosin wrote:
> > > > On 2018-05-27 11:18, Peter Rosin wrote:
> > > > > On 2018-05-25 16:51, Tudor Ambarus wrote:
> > > > > > We think the best way is to keep LCD on DDR Ports 2 and 3 (8th and 9th
> > > > > > slaves), to have maximum bandwidth and to use DMA on DDR port 1 for NAND
> > > > > > (7th slave).
> > > > >
> > > > > Exactly how do I accomplish that?
> > > > >
> > > > > I can see how I can move the LCD between slave DDR port 2 and 3 by
> > > > > selecting LCDC DMA master 8 or 9 (but according to the above it should
> > > > > not matter). The big question is how I control what slave the NAND flash
> > > > > is going to use? I find nothing in the datasheet, and the code is also
> > > > > non-transparent enough for me to figure it out by myself without
> > > > > throwing out this question first...
> >
> >   >> [...]
> >
> > > > and the output is
> > > >
> > > > atmel-nand-controller 10000000.ebi:nand-controller: using dma0chan5 for DMA transfers
> > > >
> > > > So, DMA controller 0 is in use. I still don't know if IF0, IF1 or IF2 is used
> > > > or how to find out. I guess IF2 is not in use since that does not allow any
> > > > DDR2 port as slave...
> >
> > Hello Peter,
> >
> > Thank you for all the information, I will chip in to help a little bit.
> > The Master/channel is described in the device tree. The channel has a
> > controller, a mem/periph interface and a periph ID, plus a FIFO
> > configuration.
> >
> > The dma chan number reported in the dmesg is just software.
>
> Got that, that was why I added the various additional traces in that
> horrid patch in the mail you are responding to :-)
>
> >                                                              Here is an
> > example from DT:
> > dmas = <&dma0 2 AT91_DMA_CFG_PER_ID(1)>,
> >          <&dma0 2 AT91_DMA_CFG_PER_ID(2)>;
> >
> > you can match this with the help from
> > Documentation/devicetree/bindings/dma/atmel-dma.txt:
> >
> > 1. A phandle pointing to the DMA controller.
> >
> > 2. The memory interface (16 most significant bits), the peripheral
> > interface
> > (16 less significant bits).
> >
> > 3. Parameters for the at91 DMA configuration register which are device
> >
> > dependent:
> >
> >     - bit 7-0: peripheral identifier for the hardware handshaking
> > interface. The
> >     identifier can be different for tx and rx.
> >
> >     - bit 11-8: FIFO configuration. 0 for half FIFO, 1 for ALAP, 2 for ASAP.
> >
> >
> > So , what was Tudor asking for, is your DT for the ebi node (if you are
> > using ebi), or, your NFC SRAM (Nand Flash Controller SRAM) DMA
> > devicetree chunk, so, we can figure out which type of DMA are you using.
> >
> > Normally, the ebi should be connected to both DMA0 and DMA1 on those
> > interfaces specified in DT. Which ones you want to use, depends on your
> > setup (and contention on the bus/accesses, like in your case, the HLCDC)
> >
> > Thats why we have multiple choices, to pick the right one for each case.
> > In our vanilla DT sama5d3.dtsi we do not have DMA described for ebi
> > interface.
>
> Ahh, *that* NAND DMA configuration. Of course, how silly of me...
>
> This is a setup based on the at91-linea.dtsi "CPU" board. That dtsi should
> have the relevant NAND/DMA info. Also, at91-nattis-2-natte-2.dts describes
> the older HW (with a 1024x768 panel) that is also affected, if you want a
> full device tree to look at.
>
> Looks like I didn't make a selection, quoting from at91-linea.dtsi:

Ok, so try to force the nand to use DDR port 1 : use DMAC0 or DMAC1 on 
the interfaces corresponding just to DDR port 1, and see if helps (while 
leaving HLCDC on both masters - DDR port 2 and 3).

One more thing: what are the actual nand commands which you use when you 
get the glitches? read/write/erase ... ?
What happens if you try to minimize the nand access? you also said at 
some point that only *some* nand accesses cause glitches.

Another thing : even if the LCD displays a still image, the DMA still 
feeds data to the LCD right ?

> &ebi {
> 	pinctrl-0 = <&pinctrl_ebi_nand_addr>;
> 	pinctrl-names = "default";
> 	status = "okay";
> };
>
> &nand_controller {
> 	status = "okay";
>
> 	nand: nand@3 {
> 		reg = <0x3 0x0 0x2>;
> 		atmel,rb = <0>;
> 		nand-bus-width = <8>;
> 		nand-ecc-mode = "hw";
> 		nand-ecc-strength = <4>;
> 		nand-ecc-step-size = <512>;
> 		nand-on-flash-bbt;
> 		label = "atmel_nand";
> 	};
> };
>
> The reason is probably because the sama5d3xek device-trees didn't at the
> time of "fork". Does anybody have any suggestion for some extra properties
> to try in the above nodes?
>
> Further, I forgot that I had actually upstreamed linea support for
> at91bootstrap, so relevant NAND timings etc can be found in lpddr1_init()
> in
>
> 	at91bootstrap/contrib/board/axentia/sama5d3_linea/sama5d3_linea.c
>
> Cheers,
> Peter
>
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