linux-kernel - Re: [PATCH] mtd: rawnand: omap2: Actually prevent invalid configuration and build error

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Message-ID: <20220308102619.71aa9e4e@xps13>
Date:   Tue, 8 Mar 2022 10:26:19 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Roger Quadros <rogerq@...nel.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Guenter Roeck <linux@...ck-us.net>,
        krzysztof.kozlowski@...onical.com, vigneshr@...com, nm@...com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: rawnand: omap2: Actually prevent invalid
 configuration and build error

Hi Roger,

rogerq@...nel.org wrote on Mon, 7 Mar 2022 23:05:47 +0200:

> Hi Miquel,
> 
> On 07/03/2022 16:12, Miquel Raynal wrote:
> > Hi Roger,
> > 
> > rogerq@...nel.org wrote on Mon, 7 Mar 2022 14:25:48 +0200:
> >   
> >> Hi Miquel,
> >>
> >> On 07/03/2022 12:03, Miquel Raynal wrote:  
> >>> Hi Roger,
> >>>
> >>> rogerq@...nel.org wrote on Sat, 5 Mar 2022 00:50:14 +0200:
> >>>     
> >>>> Hi Miquel,
> >>>>
> >>>> On 04/03/2022 17:54, Miquel Raynal wrote:    
> >>>>> Hi Guenter, Roger,
> >>>>>
> >>>>> rdunlap@...radead.org wrote on Sat, 26 Feb 2022 22:55:28 -0800:
> >>>>>       
> >>>>>> On 2/19/22 16:44, Guenter Roeck wrote:      
> >>>>>>> On Sat, Feb 19, 2022 at 09:36:00PM +0200, Roger Quadros wrote:        
> >>>>>>>> The root of the problem is that we are selecting symbols that have
> >>>>>>>> dependencies. This can cause random configurations that can fail.
> >>>>>>>> The cleanest solution is to avoid using select.
> >>>>>>>>
> >>>>>>>> This driver uses interfaces from the OMAP_GPMC driver so we have to
> >>>>>>>> depend on it instead.
> >>>>>>>>
> >>>>>>>> Fixes: 4cd335dae3cf ("mtd: rawnand: omap2: Prevent invalid configuration and build error")
> >>>>>>>> Signed-off-by: Roger Quadros <rogerq@...nel.org>        
> >>>>>>>
> >>>>>>> Tested-by: Guenter Roeck <linux@...ck-us.net>        
> >>>>>>
> >>>>>> Tested-by: Randy Dunlap <rdunlap@...radead.org>      
> >>>>>
> >>>>> Sorry for noticing that just now, but there is still a problem with
> >>>>> this patch: we now always compile-in the OMAP_GPMC driver whenever we
> >>>>> need the NAND controller, even though it is not needed. This grows the
> >>>>> kernel for no reason.      
> >>>>
> >>>> Sorry, I did not understand what you meant.
> >>>>
> >>>> We no longer explicitly enable OMAP_GPMC since we dropped the "select".
> >>>> This fixes all build issues that were reported recently.
> >>>>
> >>>> MTD_NAND_OMAP2 will not be enabled if OMAP_GPMC is not since we added
> >>>> the "depends on". This fixes the original build issue that we started to
> >>>> fix with select initially.    
> >>>
> >>> Yes, this side is fine.
> >>>
> >>> In the initial commit, you proposed:
> >>>
> >>> --- a/drivers/mtd/nand/raw/Kconfig
> >>> +++ b/drivers/mtd/nand/raw/Kconfig
> >>> @@ -42,7 +42,8 @@ config MTD_NAND_OMAP2
> >>>         tristate "OMAP2, OMAP3, OMAP4 and Keystone NAND controller"
> >>>         depends on ARCH_OMAP2PLUS || ARCH_KEYSTONE || ARCH_K3 || COMPILE_TEST
> >>>         depends on HAS_IOMEM
> >>> +       select OMAP_GPMC if ARCH_K3
> >>>
> >>> Which creates a dependency over OMAP_GPMC only for a single
> >>> architecture. Which means that other OMAP platforms do not necessarily
> >>> need OMAP_GPMC for the NAND controller to work. Now, you propose:    
> >>
> >> No that is not true. Other platforms that need MTD_NAND_OMAP2 are
> >> explicitly selecting OMAP_GPMC
> >> i.e. in arch/arm/mach-omap2/Kconfig  
> > 
> > Okay, in this case the fix is fine but we will need to clean this up in
> > a second time.  
> 
> What clean up are you implying here? Those legacy platform might need
> OMAP_GPMC for booting so they select it. There is nothing much we can do there.

If all the board that need the OMAP_GPMC select it, then we should just
take care that the K3 architecture does not behave differently unless
there is a good reason to do it differently. AFAIR you told me this
architecture did not select OMAP_GPMC yet.

> What is left to do now is make user/defconfig files to enable OMAP_GPMC driver
> so other platforms that don't need OMAP_GPMC for basic operation can still
> enable them later via defconfig or manually by user.

And yes, that is also what I meant to be "cleaned up" :)

> >>> --- a/drivers/mtd/nand/raw/Kconfig
> >>> +++ b/drivers/mtd/nand/raw/Kconfig
> >>> @@ -42,8 +42,7 @@ config MTD_NAND_OMAP2
> >>>  	tristate "OMAP2, OMAP3, OMAP4 and Keystone NAND controller"
> >>>  	depends on ARCH_OMAP2PLUS || ARCH_KEYSTONE || ARCH_K3 || COMPILE_TEST
> >>>  	depends on HAS_IOMEM
> >>> 	depends on OMAP_GPMC
> >>>
> >>> This means any of the other OMAP architectures will compile the GPMC
> >>> driver even though they might not need it, which would unnecessarily
> >>> increase the kernel size.
> >>>
> >>> Am I missing something?    
> >>
> >> MTD_NAND_OMAP2 NAND controller is a submodule of the OMAP GPMC IP. So it
> >> cannot work without OMAP_GPMC driver.  
> > 
> > I didn't remember exactly but in that case it's okay, I was just
> > surprised by the "select GPMC if ARCH_K3" but indeed with this
> > explanation it makes more sense.
> >   
> >> Hope this clarifies the doubts.  
> > 
> > Yes, thanks. I will send the fix to Linus then.
> > 
> > Cheers,
> > Miquèl  
> 
> cheers,
> -roger


Thanks,
Miquèl