Hi Stefan, On Mon, Feb 21, 2022 at 01:45:10PM +0100, Stefan Wahren wrote: > Am 21.02.22 um 08:10 schrieb Laurent Pinchart: > > On Mon, Feb 14, 2022 at 12:32:59PM +0100, Stefan Wahren wrote: > >> Am 14.02.22 um 10:54 schrieb Laurent Pinchart: > >>> On Mon, Feb 14, 2022 at 10:39:54AM +0100, Maxime Ripard wrote: > >>>> On Sun, Feb 13, 2022 at 04:48:45PM +0100, Stefan Wahren wrote: > >>>>> as someone with a little more insight to the clocks, i like to know your > >>>>> opinion about the bcm2835-unicam binding. > >>>>> > >>>>> Am 08.02.22 um 16:50 schrieb Jean-Michel Hautbois: > >>>>>> Introduce the dt-bindings documentation for bcm2835 CCP2/CSI2 Unicam > >>>>>> camera interface. > >>>>>> > >>>>>> Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx> > >>>>>> Signed-off-by: Naushir Patuck <naush@xxxxxxxxxxxxxxx> > >>>>>> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxxxxxxxx> > >>>>>> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > >>>>>> > >>>>>> --- > >>>>>> v4: > >>>>>> - make MAINTAINERS its own patch > >>>>>> - describe the reg and clocks correctly > >>>>>> - use a vendor entry for the number of data lanes > >>>>>> --- > >>>>>> .../bindings/media/brcm,bcm2835-unicam.yaml | 117 ++++++++++++++++++ > >>>>>> 1 file changed, 117 insertions(+) > >>>>>> create mode 100644 Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml > >>>>>> > >>>>>> diff --git a/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml b/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml > >>>>>> new file mode 100644 > >>>>>> index 000000000000..1938ace23b3d > >>>>>> --- /dev/null > >>>>>> +++ b/Documentation/devicetree/bindings/media/brcm,bcm2835-unicam.yaml > >>>>>> @@ -0,0 +1,117 @@ > >>>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > >>>>>> +%YAML 1.2 > >>>>>> +--- > >>>>>> +$id: http://devicetree.org/schemas/media/brcm,bcm2835-unicam.yaml# > >>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml# > >>>>>> + > >>>>>> +title: Broadcom BCM283x Camera Interface (Unicam) > >>>>>> + > >>>>>> +maintainers: > >>>>>> + - Raspberry Pi Kernel Maintenance <kernel-list@xxxxxxxxxxxxxxx> > >>>>>> + > >>>>>> +description: |- > >>>>>> + The Unicam block on BCM283x SoCs is the receiver for either > >>>>>> + CSI-2 or CCP2 data from image sensors or similar devices. > >>>>>> + > >>>>>> + The main platform using this SoC is the Raspberry Pi family of boards. On > >>>>>> + the Pi the VideoCore firmware can also control this hardware block, and > >>>>>> + driving it from two different processors will cause issues. To avoid this, > >>>>>> + the firmware checks the device tree configuration during boot. If it finds > >>>>>> + device tree nodes whose name starts with 'csi' then it will stop the firmware > >>>>>> + accessing the block, and it can then safely be used via the device tree > >>>>>> + binding. > >>>>>> + > >>>>>> +properties: > >>>>>> + compatible: > >>>>>> + const: brcm,bcm2835-unicam > >>>>>> + > >>>>>> + reg: > >>>>>> + items: > >>>>>> + - description: Unicam block. > >>>>>> + - description: Clock Manager Image (CMI) block. > >>>>>> + > >>>>>> + reg-names: > >>>>>> + items: > >>>>>> + - const: unicam > >>>>>> + - const: cmi > >>>>>> + > >>>>>> + interrupts: > >>>>>> + maxItems: 1 > >>>>>> + > >>>>>> + clocks: > >>>>>> + items: > >>>>>> + - description: Clock to drive the LP state machine of Unicam. > >>>>>> + - description: Clock for the VPU (core clock). > >>>>>> + > >>>>>> + clock-names: > >>>>>> + items: > >>>>>> + - const: lp > >>>>>> + - const: vpu > >>>>>> + > >>>>> > >>>>> according to this patch [1], the unicam driver only needs the VPU clock > >>>>> reference just to enforce a minimum of 250 MHz. The firmware clock > >>>>> binding and its driver is specific to the bcm2711, but the Unicam IP > >>>>> exists since bcm2835. > >>>>> > >>>>> So do you think the clock part is correct or should be the VPU clock > >>>>> optional? > >>>> > >>>> I think we should keep it mandatory. Indeed, that clock is shared with > >>>> the HVS that will change its rate on a regular basis, so even just > >>>> enforcing that 250MHz while it's on without a clock handle will be > >>>> fairly hard. > >>>> > >>>> Also, those are the constraints we have now, but having the clock handle > >>>> all the time will allow us to add any constraint we might need in the > >>>> future. > >>>> > >>>> And BCM2711 or not, the clock has probably always been there. > >>> > >>> Furthermore, regardless of what the driver needs, Unicam operates with > >>> the VPU clock, so I think it makes sense to reference it in the device > >>> tree. > >> > >> okay, as a result we need a DTS patch for bcm2835-rpi.dtsi to enable the > >> firmware clocks and its driver in this series. > > > > Can't we do that on top, enabling Unicam support for bcm2711 only first > > ? I have no idea how to deal with firmware clocks on bcm2825, and I'm > > not sure Jean-Michel even has a hardware platform to test it. > > sorry as being a bcm2835 maintainer so long, i'm not always aware of the > ambiguous meaning of bcm2835. The bcm2835-rpi.dtsi is used by all > Raspberry Pi generations. So it's sufficient to test it with a Raspberry > Pi 4, but we would gain support for all generations. > > So my request is to move the changes from bcm2711 specific dtsi to the > general dtsi. There is no need to touch any driver, please have a look > at this patch [1] to see what i had in my mind. Just compile tested. > > I hope you understand, i want to have it for all generations in one step. > > [1] - > https://github.com/lategoodbye/rpi-zero/commit/67897cc22c03204e6464d00ff4ddac6bf5dc65dc Got it. I thought changes would be needed in the firmware clocks driver, if it's just about moving the node to a different file, it's pretty easy. Thank you for taking the time to cook up a patch to educate me :-) > > If you want to send a patch series to enable firmware clocks on bcm2835, > > we'll be happy to rebase on top. -- Regards, Laurent Pinchart
