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

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Date:   Mon, 7 Mar 2022 11:03:57 +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 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:

--- 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?

> > In fact, Roger once said:
> > 
> > 	"We will figure out how to enable OMAP_GPMC for K3 architecture
> > 	some other way."
> > 
> > It turns out this is not what was finally proposed. Could we try yet
> > another solution?  
> 
> This issue is still present i.e. we cannot enable MTD_NAND_OMAP2 driver on
> K3 platform since OMAP_GPMC config is hidden and not select-able
> by user or defconfig file.
> 
> But it is not yet a deal breaker since NAND on K3 is not yet enabled upstream.
> 
> For this I think OMAP_GPMC has to be a visible config entry and select-able
> from a defconfig file as I had done initially [1].
> 
> Now we have a lot of explanation to write as to why we need to do it ;)

We certainly do :)

> [1] - https://lore.kernel.org/lkml/20211123102607.13002-3-rogerq@kernel.org/
> 

Thanks,
Miquèl