Re: [PATCH v1 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

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On 16.04.20 15:20, Arnd Bergmann wrote:
On Thu, Apr 16, 2020 at 2:40 PM Boris Brezillon
<boris.brezillon@xxxxxxxxxxxxx> wrote:
On Thu, 16 Apr 2020 15:26:51 +0300
Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:
On Thu, Apr 16, 2020 at 3:03 PM Boris Brezillon
<boris.brezillon@xxxxxxxxxxxxx> wrote:
On Thu, 16 Apr 2020 19:38:03 +0800
Note that the NAND subsystem is full of unmaintained legacy drivers, so
every time we see someone who could help us get rid or update one of
them we have to take this opportunity.

Don't we rather insist to have a MAINTAINERS record for new code to
avoid (or delay at least) the fate of the legacy drivers?


Well, that's what we do for new drivers, but the xway driver has been
added in 2012 and the policy was not enforced at that time. BTW, that
goes for most of the legacy drivers in have in the NAND subsystems
(some of them even predate the git era).

To be clear, I just checked and there's no official maintainer for this
driver. Best option would be to Cc the original author and contributors
who proposed functional changes to the code, as well as the MIPS
maintainers (Xway is a MIPS platform).

A lot of the pre-acquisition code for lantiq was contributed by Hauke
Mehrtens and John Crispin. There was an intermediate generation of
MIPS SoCs with patches posted for review  by Intel in 2018 (presumably
by the same organizatiob), but those were never resubmitted after v2
and never merged:

https://lore.kernel.org/linux-mips/20180803030237.3366-1-songjun.wu@xxxxxxxxxxxxxxx/

         Arnd


Hi,

the legacy Mips SoC had a External Bus Unit (EBU), similar to an Intel/Hitachi style bus. It was used back then for lots of things, sometimes driving Leds via 74* latches, Arcadyan used it for external reset lines and very rarely was it used for nand.

Looking at this series and comparing it with xway_nand.c we see that the init sequence is near identical. Best guess is that the mountain lion uses an internal block very similar to what the legacy mips silicon used just in a newer generation and the new proposed driver is more feature complete.

If this is the case ideally the xway_nand.c is dropped and that silicon is made working with the newer driver. Chances are that we just need to add a "support less features" style flag.

Unfortunately i no longer have the evalkit for the Mips SoCs.

   John



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