From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C173926739D for ; Mon, 24 Feb 2025 18:19:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740421198; cv=none; b=OeaT6fmtgQMeSc79TC6JYfx1w+MJu2rkLmHY0OjcJ76CigxJp/1IjaHRoy4WjDTx3zGoNqXGamYRryKj4DdHKwMSBiXU/5UvnNvcZAdN/lJs5FNZs05kpFzgoecZYYnqhBUBQHXPbzky6e+Rnyb1GaEQXGpl7ALHnSrZDdnRXgQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740421198; c=relaxed/simple; bh=kK27J7AF/PxZkIwip3JkWrXvZTvpa7zivyzu9rXyfJg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ByA9BeCHxFZvS4a2RjHTXYB+vxSNentGRO+9cblaZemHHYXlv7CMRr/IwH1q4p448yqnhm8e8TZ1ye4POv3XK+CngpGuHOzH5CJBL1YK575ptE0uk6pNvL29LzyV05Z7ADB+vePRzh/TkQXqs1OSenH/Sb5rkXIiugHN3O2omHg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=e+0W91/A; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="e+0W91/A" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 1581C455; Mon, 24 Feb 2025 19:18:27 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1740421107; bh=kK27J7AF/PxZkIwip3JkWrXvZTvpa7zivyzu9rXyfJg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=e+0W91/A5v+/8P92KB0K+lM7oYA63cQ6dmJIoTT2YKPU9g/eTPh29ZzH0VEpTq7r8 UWVGZYpboWuYEQdGQwdd3B4d/4puE3NH3ZYEjAx0PLJGnsW0sEB+pnr1washe39uYX VsEuj+acj8cxcOzG+tLNqaATa2MrQfesPJtAbBCM= Date: Mon, 24 Feb 2025 20:19:35 +0200 From: Laurent Pinchart To: Sakari Ailus Cc: Tomi Valkeinen , Mehdi Djait , dave.stevenson@raspberrypi.com, linux-media@vger.kernel.org Subject: Re: [PATCH] media: i2c: imx219: Add support for 'clock-frequency' parsing Message-ID: <20250224181935.GC6778@pendragon.ideasonboard.com> References: <2462254c-bd3f-488b-94d9-e11e16108327@ideasonboard.com> <20250224132536.GE25447@pendragon.ideasonboard.com> <20250224161640.GA6778@pendragon.ideasonboard.com> <20250224163421.GB6778@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Mon, Feb 24, 2025 at 05:06:49PM +0000, Sakari Ailus wrote: > Hi Laurent, > > On Mon, Feb 24, 2025 at 06:34:21PM +0200, Laurent Pinchart wrote: > > On Mon, Feb 24, 2025 at 04:28:47PM +0000, Sakari Ailus wrote: > > > On Mon, Feb 24, 2025 at 06:16:40PM +0200, Laurent Pinchart wrote: > > > > On Mon, Feb 24, 2025 at 02:38:35PM +0000, Sakari Ailus wrote: > > > > > On Mon, Feb 24, 2025 at 03:25:36PM +0200, Laurent Pinchart wrote: > > > > > > On Mon, Feb 24, 2025 at 12:49:48PM +0000, Sakari Ailus wrote: > > > > > > > On Mon, Feb 24, 2025 at 02:24:29PM +0200, Tomi Valkeinen wrote: > > > > > > > > On 24/02/2025 13:54, Mehdi Djait wrote: > > > > > > > > > On Mon, Feb 24, 2025 at 09:42:12AM +0000, Sakari Ailus wrote: > > > > > > > > > > On Mon, Feb 24, 2025 at 08:59:34AM +0100, Mehdi Djait wrote: > > > > > > > > > > > On Mon, Feb 24, 2025 at 01:06:49AM +0200, Laurent Pinchart wrote: > > > > > > > > > > > > On Thu, Feb 20, 2025 at 04:49:09PM +0100, Mehdi Djait wrote: > > > > > > > > > > > > > Make the clock producer reference lookup optional > > > > > > > > > > > > > > > > > > > > > > > > > > Add support for ACPI-based platforms by parsing the 'clock-frequency' > > > > > > > > > > > > > property when no clock producer is available > > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Mehdi Djait > > > > > > > > > > > > > --- > > > > > > > > > > > > > drivers/media/i2c/imx219.c | 14 ++++++++++++-- > > > > > > > > > > > > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c > > > > > > > > > > > > > index 2d54cea113e1..a876a6d80a47 100644 > > > > > > > > > > > > > --- a/drivers/media/i2c/imx219.c > > > > > > > > > > > > > +++ b/drivers/media/i2c/imx219.c > > > > > > > > > > > > > @@ -1103,12 +1103,22 @@ static int imx219_probe(struct i2c_client *client) > > > > > > > > > > > > > "failed to initialize CCI\n"); > > > > > > > > > > > > > /* Get system clock (xclk) */ > > > > > > > > > > > > > - imx219->xclk = devm_clk_get(dev, NULL); > > > > > > > > > > > > > + imx219->xclk = devm_clk_get_optional(dev, NULL); > > > > > > > > > > > > > if (IS_ERR(imx219->xclk)) > > > > > > > > > > > > > return dev_err_probe(dev, PTR_ERR(imx219->xclk), > > > > > > > > > > > > > "failed to get xclk\n"); > > > > > > > > > > > > > - imx219->xclk_freq = clk_get_rate(imx219->xclk); > > > > > > > > > > > > > + if (imx219->xclk) { > > > > > > > > > > > > > + imx219->xclk_freq = clk_get_rate(imx219->xclk); > > > > > > > > > > > > > + } else { > > > > > > > > > > > > > + ret = fwnode_property_read_u32(dev_fwnode(dev), > > > > > > > > > > > > > + "clock-frequency", > > > > > > > > > > > > > + &imx219->xclk_freq); > > > > > > > > > > > > > + if (ret) > > > > > > > > > > > > > + return dev_err_probe(dev, ret, > > > > > > > > > > > > > + "failed to get clock frequency"); > > > > > > > > > > > > > + } > > > > > > > > > > > > > + > > > > > > > > > > > > > > > > > > > > > > > > This doesn't seem specific to the imx219 driver. Could you turn this > > > > > > > > > > > > into a generic V4L2 sensor helper that would take a struct device and a > > > > > > > > > > > > clock name, and return the frequency, either retrieved from the clock, > > > > > > > > > > > > or from the clock-frequency property as a fallback ? > > > > > > > > > > > > > > > > > > > > > > > > Some drivers will also need to control the clock, so the clock should > > > > > > > > > > > > probably be returned too. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Yes, I saw that many sensor drivers have the same issue. > > > > > > > > > > > > > > > > > > > > > > I will try to make it into a generic V4L2 helper and send the patches. > > > > > > > > > > > > > > > > > > > > There are other such functions in drivers/media/v4l2-core/v4l2-common.c. > > > > > > > > > > Perhaps this is where the new helper could be located as well? > > > > > > > > > > > > > > > > > > > > > > > > > > > > I was thinking about drivers/media/v4l2-core/v4l2-fwnode.c but if > > > > > > > > > v4l2-common.c is more appropriate we can go with that. > > > > > > > > > > > > > > > > I admit I have no clue about ACPI, but why is this v4l2 specific? Why > > > > > > > > doesn't clock framework do this for us? > > > > > > > > > > > > > > The "clock-frequency" isn't really specific to ACPI but it's used on some > > > > > > > boards with DT, too, that precede the current clock bindings. Clocks aren't > > > > > > > generally available to OS in ACPI either but the sensor drivers still need > > > > > > > them. DisCo for Imaging uses "mipi-img-clock-frequency" which DisCo for > > > > > > > Imaging code deep down in the ACPI framework will offer to drivers as > > > > > > > "clock-frequency". A lot of this is actually specific to cameras. On top of > > > > > > > that, camera sensors tend to be devices that are used equally on both DT > > > > > > > and ACPI systems, it's quite uncommon elsewhere. Therefore I do think the > > > > > > > natural place for this code is actually the V4L2 framework. > > > > > > > > > > > > Can ACPI devices support programmable sensor clock frequency ? > > > > > > > > > > Do you mean sensor's external clock or PLL? And do you mean programmable > > > > > as configured in system firmware or at runtime? > > > > > > > > I mean external clock, and configurable at runtime. > > > > > > There's basically no standard API to change a clock's frequency at runtime > > > (as there is no API to handle clocks) -- which is why we have a property > > > instead of that presumed API. > > > > I wonder, for ACPI devices that have a clock-frequency property, could > > we automatically register a fixed-frequency clock ? > > That's an interesting idea. > > It still could have potential to break something even if it may be > unlikely. I don't know what others are doing with clocks (if anything) > outside cameras on ACPI. > > Maybe a case for an RFC? Doing this would be nice as we could get rid of > one of the few remaining DT/ACPI differences in sensor drivers. > > That being said, this should not hold back merging the patch. An RFC sounds good. For this specific patch, I think we agree we need a helper function. I wonder if the helper could register a fixed clock if there's no clocks property, that way we could easily change the implementation later while minimizing changes to drivers. Some sort of struct clk *devm_v4l2_sensor_clk_get(struct device *dev, const char *name); that sensor drivers would call instead of devm_clk_get(). There may be issues I don't foresee though, but maybe worth trying ? -- Regards, Laurent Pinchart