On Mon, Feb 14, 2022 at 10:39:54AM +0100, Maxime Ripard wrote: > Hi, > > 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. -- Regards, Laurent Pinchart
