Hi, Am 14.02.22 um 10:54 schrieb Laurent Pinchart: > 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. okay, as a result we need a DTS patch for bcm2835-rpi.dtsi to enable the firmware clocks and its driver in this series. Best regards
