Re: [PATCH v3 5/9] ARM: dts: stm32: add Hardware debug port (HDP) on stm32mp13
From: Clement LE GOFFIC
Date: Thu Jun 12 2025 - 09:05:09 EST
On 6/12/25 13:05, Krzysztof Kozlowski wrote:
On 12/06/2025 11:31, Clement LE GOFFIC wrote:
On 6/11/25 17:48, Krzysztof Kozlowski wrote:
On 11/06/2025 16:08, Clement LE GOFFIC wrote:
On 6/11/25 08:35, Krzysztof Kozlowski wrote:
On 10/06/2025 15:33, Clement LE GOFFIC wrote:
On 6/10/25 14:38, Krzysztof Kozlowski wrote:
On 10/06/2025 14:02, Clement LE GOFFIC wrote:
On 5/29/25 11:01, Krzysztof Kozlowski wrote:
On 28/05/2025 14:14, Clement LE GOFFIC wrote:
+ };
+
+ hdp: pinctrl@5002a000 {
+ compatible = "st,stm32mp131-hdp";
+ reg = <0x5002a000 0x400>;
+ clocks = <&rcc HDP>;
status = "disabled";
Why are you disabling it? What is missing?
Nothing is missing just disabled by default.
The node is then enabled when needed in board's dts file.
Nodes should not be disabled by default if they are complete. That's why
I asked what is missing. Drop.
Hi Krzysztof, OK I better understand now.
So yes the 'pinctrl-*' properties which are board dependent are lacking.
These are not properties of this node.
Does this mean I should add 'pinctrl-*' properties in bindings yaml file ?
I don't get it..
These properties have no meaning here, so the hardware description is
complete. You claim that you miss them thus device is incomplete is just
not correct: these properties do not belong here! They belong to the
board but even there they are totally optional. Why would they be a
required resource?
To remind: we talk here ONLY about required resources.
Yes, 'pinctrl-*' properties belongs to the board and are not required.
So nothing is missing.
This hdp node in the SoC dtsi file can be enabled by default.
But the hdp driver will probe and do nothing because without the
'pinctrl-*' properties from the board files it would not be able to
access to any pin.
Pinctrl has other features in general, including interfaces to userspace
(as pretty often combined with gpio, although not sure if relevant here).
You're right. Also HDP pinctrl has a GPO feature accessible from userspace.
But by default the HDP is not connected to any pad; it needs the board
OK, then that was the answer to my first question - what is missing.
However aren't these pads connected internally also to other parts of
the SoC (like in most other vendors)?
No, HDP "output pads" are only connected to SoC pinctrl to route outside
the internal SoC signals for debug purpose.
'pinctrl-*' properties to configure the SoC pinctrl and expose HDP on
the SoC pads.
That's why for me the enabling of the driver should be in the board file
together with the SoC pinctrl configuration.
And what are the default pad settings configured by HPD driver in
bootloader (and by bootloader I mean one of few bootloaders this is
going to be used on like U-Boot)
The default is to use the GPIO of the SoC pinctrl. The HDP is not routed
outside.
>>
The userland cannot change the pinctrl alternate function mux, this is
statically defined by the devicetree.
If you expose GPIO then userland needs this regardless of alternate mux.
IOW, board level could not configure mux because it should be always
configured to safe GPIO input.
For userland sight view, SoC GPIO are preferred instead of HDP.
HDP is only GPO not GPIO. 'pinctrl-*' properties configure at the same
time the SoC pinctrl mux to HDP and the HDP pinctrl mux to one of the
HDP functions (e.g. GPO).
Best regards,
Clément