Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead of KSEG0ADDR()

From	"Maciej W. Rozycki" <macro@linux-mips.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead of KSEG0ADDR()
Date	2016-01-09 03:40 +0100
Message-ID	<qORBE-7kb-9@gated-at.bofh.it> (permalink)
References	(3 earlier) <qOpYL-5eu-19@gated-at.bofh.it> <qOrQS-6ud-19@gated-at.bofh.it> <qOA7M-3BQ-15@gated-at.bofh.it> <qOFTR-7OQ-19@gated-at.bofh.it> <qOH9g-8Y-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, 8 Jan 2016, Rafał Miłecki wrote:

> >> > This removes some (implicit) MIPS dependencies and makes the code more
> >> > portable, whether we need it or not :)
> >>
> >> So now we have following forwardtrace:
> >> devm_ioremap_nocache
> >> ioremap_nocache
> >> __ioremap_mode
> >> __ioremap
> >> CKSEG1ADDR
> >>
> >> It results in different address than KSEG0ADDR:
> >> [    1.339752] [bcm47xxsflash_bcma_probe] KSEG0ADDR(BCMA_SOC_FLASH2):9c000000
> >> [    1.346848] [bcm47xxsflash_bcma_probe] devm_ioremap_nocache:bc000000
> >>
> >> But it still works as expected! :)
> >> [    1.609426] 6 bcm47xxpart partitions found on MTD device bcm47xxsflash
> >> [    1.616169] Creating 6 MTD partitions on "bcm47xxsflash":
> >
> >  It is a functional change though and I think the change from a cached to
> > uncached mapping (i.e. from `ioremap' to `ioremap_nocache') has to be a
> > separate patch, so that both changes can be reviewed independently.
> 
> We didn't switch from 'ioremap' but from KSEG0ADDR. What exactly
> should be a separated patch?

 See my other reply -- KSEG0ADDR (cached mapping) corresponds to 
`ioremap_cache', whereas `ioremap_nocache' (or its generic `ioremap_uc' 
alias) or plain `ioremap' correspond to KSEG1ADDR (uncached mapping).  
Consequently a change that switches from KSEG0ADDR to `ioremap_nocache' or 
`ioremap' includes a functional change along a build error (portability) 
fix.  Therefore such a change has to be split into two, so that the 
functional change can be reviewed separately from the portability fix.

  Maciej

Thread

Re: [PATCH] mtd: Make MTD_BCM47XXSFLASH to depend on MIPS "Maciej W. Rozycki" <macro@linux-mips.org> - 2016-01-07 22:10 +0100
  [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead of  KSEG0ADDR() Brian Norris <computersforpeace@gmail.com> - 2016-01-08 00:10 +0100
    Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead of KSEG0ADDR() Rafał Miłecki <zajec5@gmail.com> - 2016-01-08 09:00 +0100
      Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead  of KSEG0ADDR() "Maciej W. Rozycki" <macro@linux-mips.org> - 2016-01-08 15:10 +0100
        Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead of KSEG0ADDR() Rafał Miłecki <zajec5@gmail.com> - 2016-01-08 16:30 +0100
          Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead  of KSEG0ADDR() "Maciej W. Rozycki" <macro@linux-mips.org> - 2016-01-09 03:40 +0100
        Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead  of KSEG0ADDR() Brian Norris <computersforpeace@gmail.com> - 2016-01-08 20:00 +0100
          Re: [PATCH] mtd: bcm47xxsflash: use devm_ioremap_nocache() instead  of KSEG0ADDR() "Maciej W. Rozycki" <macro@linux-mips.org> - 2016-01-09 03:40 +0100

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