lkml.org 
[lkml]   [2022]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v2 61/66] dt-bindings: media: Add Allwinner A31 ISP bindings documentation
    Hi Paul,

    (With a question for Sakari below)

    On Fri, Mar 04, 2022 at 02:57:41PM +0100, Paul Kocialkowski wrote:
    > On Fri 04 Mar 22, 14:01, Laurent Pinchart wrote:
    > > On Tue, Mar 01, 2022 at 04:38:59PM +0100, Paul Kocialkowski wrote:
    > > > On Tue 15 Feb 22, 12:16, Laurent Pinchart wrote:
    > > > > On Tue, Feb 15, 2022 at 11:10:52AM +0100, Paul Kocialkowski wrote:
    > > > > > On Mon 14 Feb 22, 19:09, Laurent Pinchart wrote:
    > > > > > > On Mon, Feb 14, 2022 at 05:18:07PM +0100, Paul Kocialkowski wrote:
    > > > > > > > On Mon 07 Feb 22, 17:51, Laurent Pinchart wrote:
    > > > > > > > > On Sat, Feb 05, 2022 at 07:54:24PM +0100, Paul Kocialkowski wrote:
    > > > > > > > > > This introduces YAML bindings documentation for the Allwinner A31 Image
    > > > > > > > > > Signal Processor (ISP).
    > > > > > > > > >
    > > > > > > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
    > > > > > > > > > ---
    > > > > > > > > > .../media/allwinner,sun6i-a31-isp.yaml | 117 ++++++++++++++++++
    > > > > > > > > > 1 file changed, 117 insertions(+)
    > > > > > > > > > create mode 100644 Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
    > > > > > > > > >
    > > > > > > > > > diff --git a/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
    > > > > > > > > > new file mode 100644
    > > > > > > > > > index 000000000000..2d87022c43ce
    > > > > > > > > > --- /dev/null
    > > > > > > > > > +++ b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
    > > > > > > > > > @@ -0,0 +1,117 @@
    > > > > > > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
    > > > > > > > > > +%YAML 1.2
    > > > > > > > > > +---
    > > > > > > > > > +$id: http://devicetree.org/schemas/media/allwinner,sun6i-a31-isp.yaml#
    > > > > > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
    > > > > > > > > > +
    > > > > > > > > > +title: Allwinner A31 Image Signal Processor Driver (ISP) Device Tree Bindings
    > > > > > > > > > +
    > > > > > > > > > +maintainers:
    > > > > > > > > > + - Paul Kocialkowski <paul.kocialkowski@bootlin.com>
    > > > > > > > > > +
    > > > > > > > > > +properties:
    > > > > > > > > > + compatible:
    > > > > > > > > > + enum:
    > > > > > > > > > + - allwinner,sun6i-a31-isp
    > > > > > > > > > + - allwinner,sun8i-v3s-isp
    > > > > > > > > > +
    > > > > > > > > > + reg:
    > > > > > > > > > + maxItems: 1
    > > > > > > > > > +
    > > > > > > > > > + interrupts:
    > > > > > > > > > + maxItems: 1
    > > > > > > > > > +
    > > > > > > > > > + clocks:
    > > > > > > > > > + items:
    > > > > > > > > > + - description: Bus Clock
    > > > > > > > > > + - description: Module Clock
    > > > > > > > > > + - description: DRAM Clock
    > > > > > > > >
    > > > > > > > > That's interesting, does the ISP have a dedicated DRAM ?
    > > > > > > >
    > > > > > > > It doesn't, it actually uses the main DRAM with the "mbus" interconnect.
    > > > > > > > The clock is probably for the DMA engine.
    > > > > > > >
    > > > > > > > > > +
    > > > > > > > > > + clock-names:
    > > > > > > > > > + items:
    > > > > > > > > > + - const: bus
    > > > > > > > > > + - const: mod
    > > > > > > > > > + - const: ram
    > > > > > > > > > +
    > > > > > > > > > + resets:
    > > > > > > > > > + maxItems: 1
    > > > > > > > > > +
    > > > > > > > > > + ports:
    > > > > > > > > > + $ref: /schemas/graph.yaml#/properties/ports
    > > > > > > > > > +
    > > > > > > > > > + properties:
    > > > > > > > > > + port@0:
    > > > > > > > > > + $ref: /schemas/graph.yaml#/$defs/port-base
    > > > > > > > > > + description: CSI0 input port
    > > > > > > > > > +
    > > > > > > > > > + properties:
    > > > > > > > > > + reg:
    > > > > > > > > > + const: 0
    > > > > > > > > > +
    > > > > > > > > > + endpoint:
    > > > > > > > > > + $ref: video-interfaces.yaml#
    > > > > > > > > > + unevaluatedProperties: false
    > > > > > > > >
    > > > > > > > > If no other property than remote-endpoint are allowed, I'd write
    > > > > > > > >
    > > > > > > > > endpoint:
    > > > > > > > > $ref: video-interfaces.yaml#
    > > > > > > > > remote-endpoint: true
    > > > > > > > > additionalProperties: false
    > > > > > > > >
    > > > > > > > > Same below.
    > > > > > > > >
    > > > > > > > > > +
    > > > > > > > > > + additionalProperties: false
    > > > > > > > > > +
    > > > > > > > > > + port@1:
    > > > > > > > > > + $ref: /schemas/graph.yaml#/$defs/port-base
    > > > > > > > > > + description: CSI1 input port
    > > > > > > > > > +
    > > > > > > > > > + properties:
    > > > > > > > > > + reg:
    > > > > > > > > > + const: 0
    > > > > > > > >
    > > > > > > > > This should be 1.
    > > > > > > >
    > > > > > > > Correct, thanks!
    > > > > > > >
    > > > > > > > > > +
    > > > > > > > > > + endpoint:
    > > > > > > > > > + $ref: video-interfaces.yaml#
    > > > > > > > > > + unevaluatedProperties: false
    > > > > > > > > > +
    > > > > > > > > > + additionalProperties: false
    > > > > > > > > > +
    > > > > > > > > > + anyOf:
    > > > > > > > > > + - required:
    > > > > > > > > > + - port@0
    > > > > > > > > > + - required:
    > > > > > > > > > + - port@1
    > > > > > > > >
    > > > > > > > > As ports are an intrinsic property of the ISP, both should be required,
    > > > > > > > > but they don't have to be connected.
    > > > > > > >
    > > > > > > > Well the ISP does have the ability to source from either CSI0 and CSI1
    > > > > > > > but I don't really get the point of declaring both ports when only one
    > > > > > > > of the two controllers is present.
    > > > > > >
    > > > > > > If it's within an SoC I don't mind too much. What I usually insist on is
    > > > > > > declaring all ports even when no external devices are connected on the
    > > > > > > board. It may however be easier to implement things on the driver side
    > > > > > > when all the ports are declared, even for internal devices. I won't
    > > > > > > insist either way here.
    > > > > > >
    > > > > > > > > By the way, how do you select at runtime which CSI-2 RX the ISP gets its
    > > > > > > > > image stream from ? Is it configured through registers of the ISP ?
    > > > > > > >
    > > > > > > > Actually what the ISP gets is fully dependent on what is received by the
    > > > > > > > CSI controller it is connected to (which can be the mipi csi-2 controller
    > > > > > > > or its direct parallel pins), so the configuration happens on the CSI side.
    > > > > > >
    > > > > > > OK, then how do you select at runtime which CSI the ISP gets its image
    > > > > > > stream from ? :-)
    > > > > >
    > > > > > What is done in the driver is that all available csi(s) entities pads are linked
    > > > > > to a single csi sink media pad, which allows userspace to enable one or the
    > > > > > other. If there's only one, it's enabled by default.
    > > > > >
    > > > > > The actual stream source (isp_dev->proc.source) is selected at link_validate
    > > > > > time and the source bit is set in sun6i_isp_proc_enable.
    > > > > >
    > > > > > I hope this answers your question!
    > > > >
    > > > > Yes it does, thank you.
    > > > >
    > > > > While this works, it makes life a bit more complicated for userspace, as
    > > > > switching between the two sources require disabling the link first and
    > > > > then enabling the new one. This is something that caused issues in the
    > > > > libcamera simple pipeline handler, I ended up having to implement a
    > > > > workaround.
    > > >
    > > > That surprises me a bit, I thought this was a typical use-case for links.
    > > > So the fact that it's a two-step process causes issues somehow?
    > >
    > > It's not so much that the links have to be configured in two steps
    > > (although it would be nice if that could be fixed), but the fact that
    > > the order of the operations matter. Userspace has to know what
    > > combination of links is acceptable in order to determine the order of
    > > the enable/disable operations, otherwise errors may be returned. That
    > > makes it more difficult to write generic userspace code.
    >
    > Ah right, I understand that. Now it's pretty much trial-and-error if userspace
    > doesn't have prior knowledge about the hardware. But to be honest I assumed
    > that it was more or less understood that there cannot be fully generic
    > userspace for this and that knowedlege about the driver and pipeline flow
    > is required to do things right.

    You're right, and that's why we have device-specific code in libcamera.
    However, the more generic-friendly the APIs can be, the more the
    device-specific userspace code will be able to use generic helpers, so
    it still matters.

    > > > > Could you instead have two sink pads for the ISP, and select the sensor
    > > > > at stream on time instead of link validation time by checking which link
    > > > > is enabled ? If no links or both links are enabled, you can then return
    > > > > an error.
    > > >
    > > > Yes that's totally doable.
    > > >
    > > > There's a similar situation with the sun6i-csi bridge where the source pad
    > > > has two possible links: one for routing to sun6i-csi capture (video device)
    > > > and one for routing to the isp entity.
    > > >
    > > > Would that also be best represented as two pads?
    > >
    > > Are the two outputs mutually exclusive ? Sorry if I've asked before.
    >
    > I don't think you have. Yes they are mutually exclusive, only one source
    > can be selected at a time. Same situation as the ISP where the two CSI unit
    > inputs are mutually exclusive.

    On the sink (input) side that's quite common, if you have two different
    sources but a single sink, the sink can't (usually) process both sources
    at the same time. I understand that for the sun6i-csi bridge it's the
    other way around, with the bridge can output to either a DMA engine or
    to the ISP, but not both at the same time. That's less common, but can
    certainly happen. I think I'd go for two source pads in that case too.
    Sakari, any opinion ?

    > > > > Ideally I'd say such internal routing should use the new V4L2 subdev
    > > > > routing API that is currently being implemented (see [1]), but I don't
    > > > > know when it will land, and I don't want to delay your patch series.
    > > > >
    > > > > [1] https://lore.kernel.org/linux-media/20211130141536.891878-28-tomi.valkeinen@ideasonboard.com
    > > >
    > > > I'm still a bit confused what problem this is trying to solve.
    > > > My understanding was that the current pad/link API allows representing complex
    > > > topologies and switching different paths with link enable/disable.
    > >
    > > That was the intent of the MEDIA_IOC_SETUP_LINK ioctl, but we ended up
    > > with something that is fairly ill-defined, and doesn't have the ability
    > > to set multiple links atomically. It turned out to be less usable for
    > > userspace than expected. Mistakes happen (and I'll blame myself here,
    > > having designed that API) when we don't have real test cases during
    > > kernel development.
    >
    > Yeah it's hard to predict these kinds of things in advance I suppose.
    > Thanks for the heads up!
    >
    > > > > > > > > > +
    > > > > > > > > > +required:
    > > > > > > > > > + - compatible
    > > > > > > > > > + - reg
    > > > > > > > > > + - interrupts
    > > > > > > > > > + - clocks
    > > > > > > > > > + - clock-names
    > > > > > > > > > + - resets
    > > > > > > > > > +
    > > > > > > > > > +additionalProperties: false
    > > > > > > > > > +
    > > > > > > > > > +examples:
    > > > > > > > > > + - |
    > > > > > > > > > + #include <dt-bindings/interrupt-controller/arm-gic.h>
    > > > > > > > > > + #include <dt-bindings/clock/sun8i-v3s-ccu.h>
    > > > > > > > > > + #include <dt-bindings/reset/sun8i-v3s-ccu.h>
    > > > > > > > > > +
    > > > > > > > > > + isp: isp@1cb8000 {
    > > > > > > > > > + compatible = "allwinner,sun8i-v3s-isp";
    > > > > > > > > > + reg = <0x01cb8000 0x1000>;
    > > > > > > > > > + interrupts = <GIC_SPI 83 IRQ_TYPE_LEVEL_HIGH>;
    > > > > > > > > > + clocks = <&ccu CLK_BUS_CSI>,
    > > > > > > > > > + <&ccu CLK_CSI1_SCLK>,
    > > > > > > > > > + <&ccu CLK_DRAM_CSI>;
    > > > > > > > > > + clock-names = "bus", "mod", "ram";
    > > > > > > > > > + resets = <&ccu RST_BUS_CSI>;
    > > > > > > > > > +
    > > > > > > > > > + ports {
    > > > > > > > > > + #address-cells = <1>;
    > > > > > > > > > + #size-cells = <0>;
    > > > > > > > > > +
    > > > > > > > > > + port@0 {
    > > > > > > > > > + reg = <0>;
    > > > > > > > > > +
    > > > > > > > > > + isp_in_csi0: endpoint {
    > > > > > > > > > + remote-endpoint = <&csi0_out_isp>;
    > > > > > > > > > + };
    > > > > > > > > > + };
    > > > > > > > > > + };
    > > > > > > > > > + };
    > > > > > > > > > +
    > > > > > > > > > +...

    --
    Regards,

    Laurent Pinchart

    \
     
     \ /
      Last update: 2022-03-04 15:10    [W:5.259 / U:0.092 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site