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charset=us-ascii Content-Disposition: inline In-Reply-To: <20250521105141.GF12514@pendragon.ideasonboard.com> Hi Laurent, On Wed, May 21, 2025 at 12:51:41PM +0200, Laurent Pinchart wrote: > On Thu, May 15, 2025 at 11:50:19PM +0300, Sakari Ailus wrote: > > On Thu, May 15, 2025 at 03:51:33PM +0200, Mehdi Djait wrote: > > > On Thu, May 15, 2025 at 02:40:50PM +0200, Laurent Pinchart wrote: > > > > On Thu, May 15, 2025 at 11:17:37AM +0200, Mehdi Djait wrote: > > > > > On Thu, May 15, 2025 at 10:44:03AM +0200, Laurent Pinchart wrote: > > > > > > On Sat, May 10, 2025 at 04:21:09PM +0200, Hans de Goede wrote: > > > > > > > On 21-Mar-25 2:03 PM, Mehdi Djait wrote: > > > > > > > > Introduce a helper for v4l2 sensor drivers on both DT- and ACPI-based > > > > > > > > platforms to retrieve a reference to the clock producer from firmware. > > > > > > > > > > > > > > > > This helper behaves the same as clk_get_optional() except where there is > > > > > > > > no clock producer like in ACPI-based platforms. > > > > > > > > > > > > > > > > For ACPI-based platforms the function will read the "clock-frequency" > > > > > > > > ACPI _DSD property and register a fixed frequency clock with the frequency > > > > > > > > indicated in the property. > > > > > > > > > > > > > > > > Signed-off-by: Mehdi Djait > > > > > > > > > > > > > > This certainly looks quite useful, thank you for working > > > > > > > on this. > > > > > > > > > > > > > > Note on some IPU3 platforms where the clk is provided by > > > > > > > a clk-generator which is part of a special sensor-PMIC > > > > > > > the situation is a bit more complicated. > > > > > > > > > > > > > > Basically if there is both a clk provider and a clock-frequency > > > > > > > property then the clock-frequency value should be set as freq > > > > > > > to the clk-provider, see: > > > > > > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/i2c/ov8865.c#n3020 > > > > > > > > > > > > > > for an example of a driver which handles this case. > > > > > > > > > > > > On a side note, the DT bindings for the OV8865 doesn't specify the > > > > > > clock-frequency property... > > > > > > > > > > Is this wrong ? > > > > > > > > > > The OV8865 driver was introduced for DT-based systems, where you will > > > > > get a reference to the "struct clk corresponding to the clock producer" > > > > > and then get the clock-rate/frequency with a call to: > > > > > > > > > > rate = clk_get_rate(sensor->extclk); > > > > > > > > > > The patch "73dcffeb2ff9 media: i2c: Support 19.2MHz input clock in ov8865" > > > > > adding support for clock-frequency came later to support ACPI-based > > > > > systems (IPU3 here) > > > > > > > > I'd expect all device properties to be documented in DT bindings. Is > > > > that an incorrect assumption ? > > > > > > > > > > I am actually genuinely asking, is the clock-frequency a device property > > > of the ov8865 camera sensor or the clock source, which is a separate device ? > > > > The sensor's. > > > > Could we document how this is supposed to work on DT and ACPI? > > Yes please. Would you like to send a patch ? :-) I'd add this to the helper's documentation. We'll work this out with Mehdi. > > > I think we should also select COMMON_CLK on ACPI systems for sensor > > drivers (in a separate patch maybe?), instead of relying on distributions > > enabling it. > > > > > Example the imx258 with a fixed-clock, which has its own compatible > > > and DT bindings under bindings/clock/fixed-clock.yaml > > > > > > So when adding support for ACPI-based systems, the DT bindings should > > > not be changed because getting the clock-frequency from the ACPI _DSD > > > property is a workaround only needed on ACPI-based systems. > > > > I wouldn't say it's a workaround, but something that's only needed on ACPI > > systems. > > Does that mean that the clock-frequency property should be deprecated on > DT-based systems, and not used in any new sensor bindings ? I don't think we've added any "clock-frequency" properties in DT bindings for camera sensors since around 2020 or so. -- Regards, Sakari Ailus