Re: [PATCH v4 1/4] mtd: spi-nor: add memory controllers for the Aspeed AST2500 SoC

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Fri, 6 Jan 2017 11:04:12 +0100
Cédric Le Goater <clg@kaod.org> wrote:

> Hello Boris,
> 
> On 01/06/2017 09:49 AM, Boris Brezillon wrote:
> > Hi Cédric,
> > 
> > On Thu, 5 Jan 2017 14:39:14 +0100
> > Cédric Le Goater <clg@kaod.org> wrote:
> >   
> >> Hello Cyrille, Boris 
> >>
> >> On 01/04/2017 06:50 PM, Boris Brezillon wrote:  
> >>> Cyrille, Cédric,
> >>>
> >>> On Wed, 4 Jan 2017 15:52:07 +0100
> >>> Cyrille Pitchen <cyrille.pitchen@atmel.com> wrote:
> >>>     
> >>>>>       
> >>>>>> Anyway, since the review is done now, on my side I won't ask you to remove
> >>>>>> or split the support of the 'Command' mode in a separated patch.
> >>>>>> I let you do as you want, if it help you to introduce some part of the
> >>>>>> support of this 'Command' mode now even if not completed yet, no problem on
> >>>>>> my side :)
> >>>>>>
> >>>>>> I was just giving you some pieces of advice for the next time if you want
> >>>>>> to speed up the review of another patch introducing new features.
> >>>>>>
> >>>>>> However, I will just ask you one more version handling the dummy cycles
> >>>>>> properly as it would help us for the global maintenance of the spi-nor
> >>>>>> subsystem. This is the only mandatory modification I ask you, after that I
> >>>>>> think it would be ok for me and since Marek has already reviewed your
> >>>>>> driver, it would be ready to be merged into the spi-nor tree.      
> >>>>>
> >>>>> Sending a v5 which should address your comments. 
> >>>>>
> >>>>> I have removed the label property and will start a new thread in the 
> >>>>> topic. Any hints on which binding we could add this label prop ?  
> >>>>>      
> >>>>
> >>>> Here I will provide just few thoughts about this new DT property. I don't
> >>>> pretend this is what should be done. I still think other mtd maintainers
> >>>> should be involved to discuss this topic.
> >>>>
> >>>> First the DT property name "label" sounds good to me: it is consistent with
> >>>> "label" DT property used to name mtd partitions. However, I don't think it
> >>>> should be documented in jedec,spi-nor.txt but *maybe* in partition.txt as
> >>>> the purpose of this new DT property seems very close to the "label"
> >>>> property of partition nodes: let's think about some hard-disk device
> >>>> (/dev/sda) and its partition devices (/dev/sdaX).    
> >>
> >> yes this is very similar. I first looked at introducing a name to 
> >> an overall containing partition but the partition binding is not 
> >> designed for that. There are constraints on the start address and
> >> the size which does not fit the purpose.
> >>  
> >>> Hm, partition.txt may not be appropriate here. We're not documenting
> >>> the MTD partition binding, but the MTD device one. Maybe we should
> >>> create mtd.txt and put all generic MTD dev properties here.    
> >>>>
> >>>> Besides, the concept of this memory label is not limited to SPI NOR but
> >>>> could also apply to NAND memories or any other MTD handled memories.    
> >>>
> >>> Definitely. Actually I think I'll need that for the Atmel NAND
> >>> controller driver rework I'm currently working on, to keep mtdparts
> >>> parser happy even after changing the NAND device naming scheme.
> >>>     
> >>>> Hence the DT property might be handled by drivers/mtd/ofpart.c instead of
> >>>> being handled by spi-nor.c or by each SPI NOR memory controller driver.    
> >>>
> >>> Actually, that could be done at the mtdcore level in
> >>> mtd_set_dev_defaults() [1].    
> >>
> >> that would be perfect.
> >>  
> >>>> Finally, I guess we should take time to discuss and all agree what should
> >>>> be done precisely before introducing a new DT property because one general
> >>>> rule with DTB files is that users should be able to update their kernel
> >>>> image (zImage, uImage, ...) without changing their DTB: device trees should
> >>>> be backward compatible. Hence if we make a wrong choice today, we are
> >>>> likely to have to live with it and keep supporting that bad choice.    
> >>>
> >>> Rob already acked the patch, so, if all MTD maintainers agree that this
> >>> new property is acceptable, we should be fine ;-).    
> >>
> >> yes but we would need to move the binding property to another file. 
> >> What I sent applied to "jedec,spi-nor" and we want to generalize the 
> >> property to other devices.  
> > 
> > We could create an new file under
> > Documentation/devicetree/bindings/mtd/, or we could rename
> > partition.txt into something else (generic.txt or common.txt) and
> > document more than the partition binding.  
> 
> OK. 
> 
> I guess that creating a new file for a single property is a little 
> overkill or do we expect more common properties at the device level ?

Not that I can think of, but we never know.

> In that case, may be we could keep the partition.txt file and add  
> a common.txt file. If not, common.txt seems to be a good name. 
> Waiting a little for others to chime in.   
> 
> 
> > Can you take care of that (in a separate patch series of course)?  
> 
> sure, and will you send : 
> 
> 	http://code.bulix.org/p019ah-107877
> 
> in a separate patch ? 

No, you should make it part of your series ;-).