Hi Geert,
On 09.06.2016 11:20, Geert Uytterhoeven wrote:
Hi Dirk,
On Thu, Jun 9, 2016 at 10:58 AM, Dirk Behme <dirk.behme@xxxxxxxxxxxx> wrote:
On 09.06.2016 10:22, Geert Uytterhoeven wrote:
On Thu, Jun 9, 2016 at 8:56 AM, Dirk Behme <dirk.behme@xxxxxxxxxxxx>
wrote:
with the R-Car3, the pinmux/drvctrl is done at 3 places:
1. ARM trusted firmware / IPL:
https://github.com/renesas-rcar/meta-renesas/blob/jethro/meta-rcar-gen3/recipes-bsp/arm-trusted-firmware/arm-trusted-firmware/0001-add-bl2-bl31-R-Car-support.patch#L8428
2. U-Boot:
https://github.com/renesas-rcar/u-boot/blob/v2015.04/rcar-3.2.x/board/renesas/salvator-x/salvator-x.c#L116
3. Linux kernel
https://git.kernel.org/cgit/linux/kernel/git/geert/renesas-drivers.git/tree/drivers/pinctrl/sh-pfc/pfc-r8a7795.c?h=topic/gen3-latest
Now, the issue we see is that (of course?) this is not necessarily
consistent.
Therefore: What's supposed to be the correct place to do this (once)?
IMHO the kernel should take care of making sure pinctrl is configured
correctly,
independent of earlier stages in the boot process.
From previous discussions with kernel people I expected this answer ;)
In my opinion, to be able to keep the pinctrl consistent, you have to do it
in one place. To avoid issues like discussed below. And to be able to
maintain it. The consequence of this "one place" would be that the main
place is the boot loader, then. In case of the Salvator-X this would be the
ARM trusted firmware (IPL), then.
Yes, I know, kernel people see this differently, as the kernel is the only
place they have under control. From that point of view only the kernel can
"fix" broken or not updated boot loaders.
So it depends whether you have only the kernel or everything under your
control, including the boot loader.
Note that if the kernel takes care of it, doing it once is not an option,
as
earlier stages may need pinctrl configuration depending on boot method
(e.g. TFTP over Ethernet needs RAVB setup).
How will the kernel handle different boards needing different pinctrl
configuration?
I.e. how is pfc-r8a7795 supposed to cover different boards?
Pinctrl for devices is described in the board's DTS (e.g.
r8a7795-salvator-x.dts).
Or in a DT overlay, if you use the EXIO connectors.
The example is the RAVB ethernet: We found that on the Salvator-X the
kernel's ethernet doesn't work without being initialized by U-Boot. I.e.
without running U-Boot doing the drvctrl [1] ethernet fails in the Linux
kernel.
This is a missing/incorrect drive strength configuration?
Yes, I think so.
The pfc-r8a7795 does have support for drive strength, but only for pins
that
also have GPIO capabilities. (At least some of) the RAVB pins don't seem
to be handled (e.g. DRVCTRL2).
So your proposal would be to fix/correct/extend Linux kernel's pfc-r8a7795
to correctly support the drive strength needed for the RAVB on the
Salvator-X?
No, you need more steps.
1. Add non-GPIO drive strength support to pfc-r8a7795,
2. Describe correct RAVB pinctrl config in r8a7795-salvator-x.dts.
3. Profit!
I think we will go with fixing the boot loader, then :)
Best regards
Dirk
