On Mon, Feb 21, 2022 at 09:10:27AM +0200, Laurent Pinchart wrote: > 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. The RPi kernel uses the firmware clocks driver for all the platforms, so it shouldn't be too bad. Maxime
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