[linux-sunxi] Re: [PATCH 05/11] drivers: pinctrl: add driver for Allwinner A64 SoC

[Maxime Ripard]

Hi,

On Tue, Feb 02, 2016 at 03:58:52AM +0200, Siarhei Siamashka wrote:
> > > On Mon, Feb 01, 2016 at 05:39:24PM +0000, Andre Przywara wrote:  
> > >> Based on the Allwinner A64 user manual and on the previous sunxi
> > >> pinctrl drivers this introduces the pin multiplex assignments for
> > >> the ARMv8 Allwinner A64 SoC.
> > >> Port A is apparently used for the fixed function DRAM controller, so
> > >> the ports start at B here (the manual mentions "n from 1 to 7", so
> > >> not starting at 0).
> > >>
> > >> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> > >> ---
> > >>  .../bindings/pinctrl/allwinner,sunxi-pinctrl.txt   |   1 +
> > >>  arch/arm64/Kconfig.platforms                       |   1 +
> > >>  drivers/pinctrl/sunxi/Kconfig                      |   4 +
> > >>  drivers/pinctrl/sunxi/Makefile                     |   1 +
> > >>  drivers/pinctrl/sunxi/pinctrl-a64.c                | 606 +++++++++++++++++++++
> > >>  5 files changed, 613 insertions(+)
> > >>  create mode 100644 drivers/pinctrl/sunxi/pinctrl-a64.c
> > >>
> > >> diff --git a/Documentation/devicetree/bindings/pinctrl/allwinner,sunxi-pinctrl.txt b/Documentation/devicetree/bindings/pinctrl/allwinner,sunxi-pinctrl.txt
> > >> index 9213b27..9050002 100644
> > >> --- a/Documentation/devicetree/bindings/pinctrl/allwinner,sunxi-pinctrl.txt
> > >> +++ b/Documentation/devicetree/bindings/pinctrl/allwinner,sunxi-pinctrl.txt
> > >> @@ -21,6 +21,7 @@ Required properties:
> > >>    "allwinner,sun9i-a80-r-pinctrl"
> > >>    "allwinner,sun8i-a83t-pinctrl"
> > >>    "allwinner,sun8i-h3-pinctrl"
> > >> +  "allwinner,a64-pinctrl"  
> > > 
> > > Hello,
> > > 
> > > on all other Allwinner SoCs we use the SoC family as part of the
> > > compatible, as well as in the names of the Kconfig options. To
> > > keep things consistent, I would like to propose doing the same on
> > > Arm64, i.e. using allwinner,sun50i-a64-pinctrl instead of
> > > allwinner,a64-pinctrl.  
> > 
> > Yes, I have been told this already. However I don't like this idea so
> > much, for the following reasons:
> > a) It is mostly redundant. The actual SoC (marketing) name is unique,
> > there is no sun6i-a20 or sun7i-a23.
> > b) It is not even helpful. If I got Maxime correctly, then the newer
> > sunxi generation numbers depend on the ARM _cores_ used in the SoC,
> > which is frankly the least interesting part from a Linux support
> > perspective. I would see some sense if it would reflect the generation
> > of IP blocks used, but so it is even more confusing to see that
> > sun7i-a20 and sun8i-a23 are related, but sun8i-h3 is a completely
> > different beast. The Allwinner marketing name tells you that, but the
> > sunxi one does not.
> > c) It is very confusing for people not dealing with it everyday. Just
> > because I own a BananaPi I know that the A20 is sun7i, but I am totally
> > lost when it comes to all the other names. And even now it took me about
> > a minute to find the appropriate Wiki page which explains part of that
> > story.
> > d) Most importantly ;-): It kills TAB completion, unless you know the
> > sunxi number, which is mostly not true as pointed out in c)
> > 
> > So while I see that just a<somenumber> is not really very specific, I'd
> > rather do away with current naming scheme for the future. In this
> > particular case we have the vendor name as a name space identifier
> > already, so there is no possible confusion with ARM Cortex naming, for
> > instance.
> > 
> > Also as this is now moving into the arm64 world, I'd like to use the
> > opportunity to fix things that are not really optimal, the naming is one
> > of them.
> 
> One of the problems is that A64 name is not unique. We have reasons
> to believe that there are also H64 and R18 out there using exactly
> the same die, but possibly available in different packaging (a different
> ball grid pitch? or maybe a different set of peripherals routed to the
> outside?). Early prototypes of the Pine64 board were using Allwinner R18
> and the Jide Remix Mini HTPC box is using Allwinner H64.
> 
> The bootloader sources from Allwinner are also referring to A64 as
> AW1689, which makes some sense because it is the chip id number that
> is accessible for runtime identification via reading the SRAM_VER_REG
> hardware register:
> 
>     http://linux-sunxi.org/SRAM_Controller_Register_Guide#SRAM_VER_REG
> 
> So would it be a good idea to use "aw1689" as a compatible property
> in the DT instead of "a64"? Or maybe have "aw1689-a64" and
> "aw1689-h64", which would be similar to the existing "sun5i-a13"
> and "sun5i-a10s" naming convention?

If someone cannot find out the family name that is documented on
several places, I'm not sure he'll find the obscure, internal code
name.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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