Re: [PATCH] Documentation: binding: Update endianness usage

Re: [PATCH] Documentation: binding: Update endianness usage

[Scott Wood]

On Mon, 2017-12-04 at 04:33 +0000, Prabhakar Kushwaha wrote:
> > -----Original Message-----
> > From: Scott Wood [mailto:oss@buserror.net]
> > Sent: Saturday, December 02, 2017 3:25 AM
> > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > mtd@lists.infradead.org; devicetree-discuss@lists.ozlabs.org
> > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > 
> > On Fri, 2017-12-01 at 08:42 +0000, Prabhakar Kushwaha wrote:
> > > > -----Original Message-----
> > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > Sent: Friday, December 01, 2017 10:43 AM
> > > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > > mtd@lists.infradead.org; devicetree-discuss@lists.ozlabs.org
> > > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > > > 
> > > > If big endian is the default, is this change really
> > > > necessary?  Particularly
> > > > since the big endian chips are older and thus have existing device
> > > > trees.
> > > > 
> > > 
> > > Earlier endianness information was only used for "how to"  access IFC-
> > > NAND
> > > register access.
> > > Now this info  will also be used for defining swap requirement of NOR
> > > flash.
> > 
> > Is this a difference between LS1021A and PPC-based chips?
> > 
> 
> Yes. 
> CONFIG_MTD_CFI_BE_BYTE_SWAP needs to be defined For LS1021A, LS1043A,
> LS1046A  

Only because you're running a little-endian kernel on those chips.  I still
don't see why the absence of a little-endian property isn't sufficient to
communicate that the hardware is big-endian given that that's the established
default.

I now see your patch to of_flash_probe... where is the non-IFC-specific
binding that says the *parent* of a CFI node should be looked at for this? 
Where in general are endian properties kept in the parent of the node with
"reg"?  The right answer is to add endianness to mtd-physmap.txt.

-Scott


______________________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-mtd/

RE: [PATCH] Documentation: binding: Update endianness usage

[Prabhakar Kushwaha]

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[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 2924 bytes --]


> -----Original Message-----
> From: Scott Wood [mailto:oss@buserror.net]
> Sent: Tuesday, December 05, 2017 8:16 AM
> To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> mtd@lists.infradead.org; devicetree@vger.kernel.org
> Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> 
> On Mon, 2017-12-04 at 04:33 +0000, Prabhakar Kushwaha wrote:
> > > -----Original Message-----
> > > From: Scott Wood [mailto:oss@buserror.net]
> > > Sent: Saturday, December 02, 2017 3:25 AM
> > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > mtd@lists.infradead.org; devicetree-discuss@lists.ozlabs.org
> > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > >
> > > On Fri, 2017-12-01 at 08:42 +0000, Prabhakar Kushwaha wrote:
> > > > > -----Original Message-----
> > > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > > Sent: Friday, December 01, 2017 10:43 AM
> > > > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > > > mtd@lists.infradead.org; devicetree-discuss@lists.ozlabs.org
> > > > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > > > >
> > > > > If big endian is the default, is this change really
> > > > > necessary?  Particularly
> > > > > since the big endian chips are older and thus have existing device
> > > > > trees.
> > > > >
> > > >
> > > > Earlier endianness information was only used for "how to"  access IFC-
> > > > NAND
> > > > register access.
> > > > Now this info  will also be used for defining swap requirement of NOR
> > > > flash.
> > >
> > > Is this a difference between LS1021A and PPC-based chips?
> > >
> >
> > Yes.
> > CONFIG_MTD_CFI_BE_BYTE_SWAP needs to be defined For LS1021A, LS1043A,
> > LS1046A
> 
> Only because you're running a little-endian kernel on those chips.  I still
> don't see why the absence of a little-endian property isn't sufficient to
> communicate that the hardware is big-endian given that that's the established
> default.
> 
> I now see your patch to of_flash_probe... where is the non-IFC-specific
> binding that says the *parent* of a CFI node should be looked at for this?
> Where in general are endian properties kept in the parent of the node with
> "reg"?  The right answer is to add endianness to mtd-physmap.txt.
> 

Flashes are always littler endian. 
It is because of IFC controller behavior, endianness is required.  
So as per my understanding, this info should go in IFC binding. 

Please help me if I am not able to understand your view.

--prabhakar


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Re: [PATCH] Documentation: binding: Update endianness usage

[Scott Wood]

On Tue, 2017-12-05 at 09:45 +0000, Prabhakar Kushwaha wrote:
> > -----Original Message-----
> > From: Scott Wood [mailto:oss-fOR+EgIDQEHk1uMJSBkQmQ@public.gmane.org]
> > Sent: Tuesday, December 05, 2017 8:16 AM
> > To: Prabhakar Kushwaha <prabhakar.kushwaha-3arQi8VN3Tc@public.gmane.org>; linux-
> > mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org; devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > Cc: dedekind1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org; computersforpeace-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > 
> > I now see your patch to of_flash_probe... where is the non-IFC-specific
> > binding that says the *parent* of a CFI node should be looked at for this?
> > Where in general are endian properties kept in the parent of the node with
> > "reg"?  The right answer is to add endianness to mtd-physmap.txt.
> > 
> 
> Flashes are always littler endian. 

We wouldn't be having this discussion if that were true...  This is about how
it presents to the CPU, not about how the actual pins on the chip are
numbered.

> It is because of IFC controller behavior, endianness is required.  
> So as per my understanding, this info should go in IFC binding. 

If the info should go in the IFC binding why is the code in a non-IFC-specific 
place?

-Scott

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RE: [PATCH] Documentation: binding: Update endianness usage

[Prabhakar Kushwaha]

> -----Original Message-----
> From: Scott Wood [mailto:oss@buserror.net]
> Sent: Wednesday, December 06, 2017 1:38 AM
> To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> mtd@lists.infradead.org; devicetree@vger.kernel.org
> Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> 
> On Tue, 2017-12-05 at 09:45 +0000, Prabhakar Kushwaha wrote:
> > > -----Original Message-----
> > > From: Scott Wood [mailto:oss@buserror.net]
> > > Sent: Tuesday, December 05, 2017 8:16 AM
> > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > >
> > > I now see your patch to of_flash_probe... where is the non-IFC-specific
> > > binding that says the *parent* of a CFI node should be looked at for this?
> > > Where in general are endian properties kept in the parent of the node with
> > > "reg"?  The right answer is to add endianness to mtd-physmap.txt.
> > >
> >
> > Flashes are always littler endian.
> 
> We wouldn't be having this discussion if that were true...  This is about how
> it presents to the CPU, not about how the actual pins on the chip are
> numbered.
> 

Got your point :)

> > It is because of IFC controller behavior, endianness is required.
> > So as per my understanding, this info should go in IFC binding.
> 
> If the info should go in the IFC binding why is the code in a non-IFC-specific
> place?
> 

Now I understand your point.  
So I should be moving endianness property detail in mtd-physmap.txt. 

Is my understanding correct?

--prabhakar


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

RE: [PATCH] Documentation: binding: Update endianness usage

[Prabhakar Kushwaha]

> -----Original Message-----
> From: Prabhakar Kushwaha
> Sent: Wednesday, December 06, 2017 4:05 PM
> To: 'Scott Wood' <oss@buserror.net>; linux-mtd@lists.infradead.org;
> devicetree@vger.kernel.org
> Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> Subject: RE: [PATCH] Documentation: binding: Update endianness usage
> 
> 
> > -----Original Message-----
> > From: Scott Wood [mailto:oss@buserror.net]
> > Sent: Wednesday, December 06, 2017 1:38 AM
> > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> >
> > On Tue, 2017-12-05 at 09:45 +0000, Prabhakar Kushwaha wrote:
> > > > -----Original Message-----
> > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > Sent: Tuesday, December 05, 2017 8:16 AM
> > > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > > >
> > > > I now see your patch to of_flash_probe... where is the non-IFC-specific
> > > > binding that says the *parent* of a CFI node should be looked at for this?
> > > > Where in general are endian properties kept in the parent of the node with
> > > > "reg"?  The right answer is to add endianness to mtd-physmap.txt.
> > > >
> > >
> > > Flashes are always littler endian.
> >
> > We wouldn't be having this discussion if that were true...  This is about how
> > it presents to the CPU, not about how the actual pins on the chip are
> > numbered.
> >
> 
> Got your point :)
> 
> > > It is because of IFC controller behavior, endianness is required.
> > > So as per my understanding, this info should go in IFC binding.
> >
> > If the info should go in the IFC binding why is the code in a non-IFC-specific
> > place?
> >
> 
> Now I understand your point.
> So I should be moving endianness property detail in mtd-physmap.txt.
> 
> Is my understanding correct?
> 

A second thought,  
IFC binding was updated because there is no IFC-NOR driver. It uses generic Flash framework.  
 
I am just trying to get more understanding.  

--prabhakar

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

RE: [PATCH] Documentation: binding: Update endianness usage

[Prabhakar Kushwaha]

Hi Scott,


> -----Original Message-----
> From: devicetree-owner@vger.kernel.org [mailto:devicetree-
> owner@vger.kernel.org] On Behalf Of Prabhakar Kushwaha
> Sent: Wednesday, December 06, 2017 4:29 PM
> To: Scott Wood <oss@buserror.net>; linux-mtd@lists.infradead.org;
> devicetree@vger.kernel.org
> Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> Subject: RE: [PATCH] Documentation: binding: Update endianness usage
> 
> 
> 
> > -----Original Message-----
> > From: Prabhakar Kushwaha
> > Sent: Wednesday, December 06, 2017 4:05 PM
> > To: 'Scott Wood' <oss@buserror.net>; linux-mtd@lists.infradead.org;
> > devicetree@vger.kernel.org
> > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > Subject: RE: [PATCH] Documentation: binding: Update endianness usage
> >
> >
> > > -----Original Message-----
> > > From: Scott Wood [mailto:oss@buserror.net]
> > > Sent: Wednesday, December 06, 2017 1:38 AM
> > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > >
> > > On Tue, 2017-12-05 at 09:45 +0000, Prabhakar Kushwaha wrote:
> > > > > -----Original Message-----
> > > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > > Sent: Tuesday, December 05, 2017 8:16 AM
> > > > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > > > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > > > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > > > >
> > > > > I now see your patch to of_flash_probe... where is the non-IFC-specific
> > > > > binding that says the *parent* of a CFI node should be looked at for this?
> > > > > Where in general are endian properties kept in the parent of the node
> with
> > > > > "reg"?  The right answer is to add endianness to mtd-physmap.txt.
> > > > >
> > > >
> > > > Flashes are always littler endian.
> > >
> > > We wouldn't be having this discussion if that were true...  This is about how
> > > it presents to the CPU, not about how the actual pins on the chip are
> > > numbered.
> > >
> >
> > Got your point :)
> >
> > > > It is because of IFC controller behavior, endianness is required.
> > > > So as per my understanding, this info should go in IFC binding.
> > >
> > > If the info should go in the IFC binding why is the code in a non-IFC-specific
> > > place?
> > >
> >
> > Now I understand your point.
> > So I should be moving endianness property detail in mtd-physmap.txt.
> >
> > Is my understanding correct?
> >
> 
> A second thought,
> IFC binding was updated because there is no IFC-NOR driver. It uses generic Flash
> framework.
> 
> I am just trying to get more understanding.
> 

Do you have any comment/concern on this patch.
May I go ahead and request for the merger of updated patch i.e. https://patchwork.kernel.org/patch/10084331/

--prabhakar 

RE: [PATCH] Documentation: binding: Update endianness usage

[Prabhakar Kushwaha]

Hi Scott,
> -----Original Message-----
> From: Prabhakar Kushwaha
> Sent: Thursday, December 21, 2017 10:50 AM
> To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; Scott Wood
> <oss@buserror.net>; linux-mtd@lists.infradead.org; devicetree@vger.kernel.org
> Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> Subject: RE: [PATCH] Documentation: binding: Update endianness usage
> 
> Hi Scott,
> 
> 
> > -----Original Message-----
> > From: devicetree-owner@vger.kernel.org [mailto:devicetree-
> > owner@vger.kernel.org] On Behalf Of Prabhakar Kushwaha
> > Sent: Wednesday, December 06, 2017 4:29 PM
> > To: Scott Wood <oss@buserror.net>; linux-mtd@lists.infradead.org;
> > devicetree@vger.kernel.org
> > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > Subject: RE: [PATCH] Documentation: binding: Update endianness usage
> >
> >
> >
> > > -----Original Message-----
> > > From: Prabhakar Kushwaha
> > > Sent: Wednesday, December 06, 2017 4:05 PM
> > > To: 'Scott Wood' <oss@buserror.net>; linux-mtd@lists.infradead.org;
> > > devicetree@vger.kernel.org
> > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > Subject: RE: [PATCH] Documentation: binding: Update endianness usage
> > >
> > >
> > > > -----Original Message-----
> > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > Sent: Wednesday, December 06, 2017 1:38 AM
> > > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > > >
> > > > On Tue, 2017-12-05 at 09:45 +0000, Prabhakar Kushwaha wrote:
> > > > > > -----Original Message-----
> > > > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > > > Sent: Tuesday, December 05, 2017 8:16 AM
> > > > > > To: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>; linux-
> > > > > > mtd@lists.infradead.org; devicetree@vger.kernel.org
> > > > > > Cc: dedekind1@gmail.com; computersforpeace@gmail.com
> > > > > > Subject: Re: [PATCH] Documentation: binding: Update endianness usage
> > > > > >
> > > > > > I now see your patch to of_flash_probe... where is the non-IFC-specific
> > > > > > binding that says the *parent* of a CFI node should be looked at for
> this?
> > > > > > Where in general are endian properties kept in the parent of the node
> > with
> > > > > > "reg"?  The right answer is to add endianness to mtd-physmap.txt.
> > > > > >
> > > > >
> > > > > Flashes are always littler endian.
> > > >
> > > > We wouldn't be having this discussion if that were true...  This is about how
> > > > it presents to the CPU, not about how the actual pins on the chip are
> > > > numbered.
> > > >
> > >
> > > Got your point :)
> > >
> > > > > It is because of IFC controller behavior, endianness is required.
> > > > > So as per my understanding, this info should go in IFC binding.
> > > >
> > > > If the info should go in the IFC binding why is the code in a non-IFC-specific
> > > > place?
> > > >
> > >
> > > Now I understand your point.
> > > So I should be moving endianness property detail in mtd-physmap.txt.
> > >
> > > Is my understanding correct?
> > >
> >
> > A second thought,
> > IFC binding was updated because there is no IFC-NOR driver. It uses generic
> Flash
> > framework.
> >
> > I am just trying to get more understanding.
> >
> 
> Do you have any comment/concern on this patch.
> May I go ahead and request for the merger of updated patch i.e.
> https://patchwork.kernel.org/patch/10084331/
> 

Please let me know if you have any concern on this patch. 

--prabhakar