[U-Boot] [PATCH v3 5/5] ARM: dm: spi: Add support DM/DTS for i.MX28 mxs SPI driver (DM_SPI conversion)

[Lukasz Majewski <lukma@denx.de>]

On Mon, 17 Jun 2019 15:23:55 +0200
Marek Vasut <marex@denx.de> wrote:

> On 6/17/19 2:27 PM, Lukasz Majewski wrote:
> > Hi Marek,
> >   
> >> On 6/17/19 8:49 AM, Lukasz Majewski wrote:  
> >>> Hi Marek,
> >>>     
> >>>> On 6/16/19 12:34 AM, Lukasz Majewski wrote:    
> >>>>> This commit converts mxs_spi driver to support DM/DTS.
> >>>>>
> >>>>> Signed-off-by: Lukasz Majewski <lukma@denx.de>      
> >>>>
> >>>> Is the non-DM part needed for anything ?     
> >>>
> >>> Do you mean the non-DM part of the mxs_gpio driver? Yes, it is
> >>> used by not converted boards.    
> >>
> >> This is a SPI driver though.
> >>  
> >>>> I recall the SPL jumps back
> >>>> to BootROM when loading the U-Boot proper. So if not, drop it.
> >>>>
> >>>> Also, please don't do partial conversion for iMX28 only, do the
> >>>> iMX23 part as well, it cannot be hard.    
> >>>
> >>> Maybe it is not hard, but I cannot test it properly as I don't
> >>> have i.MX23 device. If you are offering your help with testing
> >>> (i.e. you do have the access to i.MX23 device and you will test
> >>> those changes) I can add support for it.
> >>>
> >>> Otherwise, NO, I will not add ANY new untested code.    
> >>
> >> In general, you don't have to add any code, the iMX23/28 SPI IP is
> >> very much the same hardware, DTTO for most of the other blocks. If
> >> there are any differences between iMX23/28, they are already
> >> handled in the existing driver(s).
> >>
> >> Half-way converted drivers in fact increase maintenance burden,
> >> because then we have to deal with two different variants of the
> >> code, instead of only one.  
> > 
> > I cannot agree with this sentence.  
> 
> Do you think maintaining - one DM driver which supports both iMX23 and
> iMX28 - is more burden than maintaining - one driver which supports
> DM, but only for iMX28 and non-DM for iMX23 and iMX28 ? I don't think
> so.
> 
> > The conversion would be done for
> > i.MX28, which is then tested and validated (and clearly stated in
> > the cover letter/commit message that only supported was i.MX28).>
> > If I don't need to adjust common, reused code (which already
> > supports both variants as it is the case with mxs_spi.c), then I
> > don't mind.  
> 
> Well, that is what I said above, you don't.

To make myself clear - If I can reuse the common code (which supports
both imx23 and 28) for DM/DTS conversion then I'm OK with doing so.

If you require me to add untested code specific to i.MX23 - then NO.

> 
> > For more intrusive changes - the driver needs to be tested and
> > validated (by somebody who has the HW for testing).  
> 
> That's up to board maintainers.
> 
> >> That's why I would like to see this practice go
> >> away wherever possible, and in this case it is possible.  
> > 
> > In this particular case it is possible to add support for both as
> > SoC specific changes (i.MX23 vs i.MX28) is performed in common code
> > (e.g. mxs_spi_xfer_dma).  
> 
> Both SPI and DMA blocks are basically the same on iMX23 and iMX28.

If I can reuse the common code, then I'm fine to do it.

> 
> >> If you need someone to test your changes, CC the board maintainers,
> >> that's standard practice.  
> > 
> > As fair as I remember only Angelo and Michael had also interest in
> > testing converted code for i.MX28 based board.
> > 
> > There was NO reply from other people when this (and few others)
> > driver was marked as DEPRECATED.  
> 
> Well, too bad, clearly the interest in this platform is low.

This means that people are using either some old U-Boot version, or
there are a few people who want to refurbish the old HW with new code
(e.g. Michael, Angelo).

> That does not mean we should do sub-par upstream work, does it ?
> 

We shall not add untested code.



Best regards,

Lukasz Majewski

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