linux-kernel - Re: [PATCH v4 02/10] media: platform: Add c3 mipi csi2 driver

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Message-ID: <2jc3sqihnj7sd7vjj7542nntc45eratyxi7diuaewlbqqbixbp@vlgkpv6vm6wr>
Date: Thu, 12 Dec 2024 10:41:42 +0100
From: Jacopo Mondi <jacopo.mondi@...asonboard.com>
To: Keke Li <keke.li@...ogic.com>
Cc: Jacopo Mondi <jacopo.mondi@...asonboard.com>, 
	Laurent Pinchart <laurent.pinchart@...asonboard.com>, Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, linux-media@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, kieran.bingham@...asonboard.com, 
	dan.scally@...asonboard.com
Subject: Re: [PATCH v4 02/10] media: platform: Add c3 mipi csi2 driver

Hi Keke

On Thu, Dec 12, 2024 at 05:08:27PM +0800, Keke Li wrote:
>
> On 2024/12/12 16:41, Jacopo Mondi wrote:
> > [ EXTERNAL EMAIL ]
> >
> > Hi Keke,
> >    a question for Laurent and Sakari
> >
> > On Thu, Dec 05, 2024 at 05:04:28PM +0800, Keke Li via B4 Relay wrote:
> > > From: Keke Li <keke.li@...ogic.com>
> > >
> > > This driver is used to receive mipi data from image sensor.
> > >
> > > Reviewed-by: Daniel Scally <dan.scally@...asonboard.com>
> > > Signed-off-by: Keke Li <keke.li@...ogic.com>
> > [snip]
> >
> > > +
> > > +static int c3_mipi_csi_configure_clocks(struct csi_device *csi)
> > > +{
> > > +     const struct csi_info *info = csi->info;
> > > +     int ret;
> > > +     u32 i;
> > > +
> > > +     for (i = 0; i < info->clock_num; i++)
> > > +             csi->clks[i].id = info->clocks[i];
> > > +
> > > +     ret = devm_clk_bulk_get(csi->dev, info->clock_num, csi->clks);
> > > +     if (ret)
> > > +             return ret;
> > > +
> > > +     for (i = 0; i < info->clock_num; i++) {
> > > +             if (!info->clock_rates[i])
> > > +                     continue;
> > > +             ret = clk_set_rate(csi->clks[i].clk, info->clock_rates[i]);
> > > +             if (ret) {
> > > +                     dev_err(csi->dev, "Failed to set %s rate %u\n", info->clocks[i],
> > > +                             info->clock_rates[i]);
> > > +                     return ret;
> > > +             }
> > > +     }
> > > +
> > > +     return 0;
> > > +}
> > > +
> > [snip]
> >
> > > +
> > > +static const struct csi_info c3_mipi_csi_info = {
> > > +     .clocks = {"vapb", "phy0"},
> > > +     .clock_rates = {0, 200000000},
> > > +     .clock_num = 2
> > > +};
> > > +
> > > +static const struct of_device_id c3_mipi_csi_of_match[] = {
> > > +     { .compatible = "amlogic,c3-mipi-csi2",
> > > +       .data = &c3_mipi_csi_info,
> > > +     },
> > > +     { },
> > > +};
> > All the drivers in this patch series implement the same pattern when
> > it comes to handling clock. There's a list of clock providers in the
> > driver associated with a clock frequency. The driver bulk_get the
> > clocks and set_rate() using the per-compatible info table.
> >
> > Do you think this should rather come from dts using the
> > assigned-clocks and assigned-clock-rates properties ?
>
> Yes,  I think your suggestion is OK.
>
> Will test it.
>
> If apply your suggestion, do I need to modify the relevant yaml file?
>

Do you mean the binding files ?

You could add to the example

--- a/Documentation/devicetree/bindings/media/amlogic,c3-isp.yaml
+++ b/Documentation/devicetree/bindings/media/amlogic,c3-isp.yaml
@@ -73,6 +73,8 @@ examples:
             clocks = <&clkc_periphs CLKID_VAPB>,
                      <&clkc_periphs CLKID_ISP0>;
             clock-names = "vapb", "isp0";
+            assigned-clocks = <&clkc_periphs CLKID_ISP0>;
+            assigned-clock-rates = <400000000>;
             interrupts = <GIC_SPI 145 IRQ_TYPE_EDGE_RISING>;

             port {


As your binding document has "additionalProperties: false" I thought
you had to add:

  assigned-clocks: true
  assigned-clock-rates: true

As in my understanding "additionalProperties: false" means "whatever
is not explicitly allowed is forbidden". However I might be wrong as
validating the binding even without the two above entries work well
(and I see other bindings doing the same)

DT maintainers are in cc