On 05/14/2018 12:01 AM, Linus Walleij wrote:
On Wed, May 9, 2018 at 11:44 AM, Alexander Graf <agraf@xxxxxxx> wrote:
On 05/07/2018 08:31 PM, Bjorn Andersson wrote:
Can you please name platform that has enough support for Alexander to
care about backwards and forwards compatibility but lacks a pinctrl
driver.
ZynqMP is one example that immediately comes to my mind. I'm sure there are
others too.
Why isn't that using drivers/pinctrl/pinctrl-zynq.c?
How is it so very different from (old) Zynq as it is already using
the same GPIO driver?
That one is very simple: ZynqMP is usually an AMP system where Linux
doesn't have full knowledge of the overall system. IIUC they have a tiny
microblaze (PMU) that does the actual full system configuration for
peripherals that may interfere with each other. This architecture also
allows for safety critical code to run alongside a (less safe) Linux system.
I think we'll see architectures like this pop up more over time. TI
Sitara has similar issues. I know that Jailhouse ran into exactly that
problem before. I also know that during Linaro Connect Budapest even the
OP-TEE people realized the current model is bad, because Linux may
control pins/clocks/etc of devices that the secure world wants to use.
So I actually believe we will see more SoCs in the future that may even
start with Linux controllable pinctrl or no pinctrl driver but then will
move to firmware controlled drivers once it starts being necessary.
Alex
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