Hi Stefan, 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. 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
