From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B302CC433F5 for ; Sun, 13 Mar 2022 14:17:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233161AbiCMOSL (ORCPT ); Sun, 13 Mar 2022 10:18:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60598 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231871AbiCMOSK (ORCPT ); Sun, 13 Mar 2022 10:18:10 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8BC79FF8 for ; Sun, 13 Mar 2022 07:17:02 -0700 (PDT) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id DA4B1475; Sun, 13 Mar 2022 15:17:00 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1647181021; bh=66NGFpYc3E28AeVvKlPCMXF/BQauU2t2rRiJU6lobSw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=luYJEFM0GXmTGm6HIyZktSFQmSs6rUx2A9cf5MY0S0zmp94D7WKnRA5uzc1r92pON 5s23bkUamCexhdjgCL6NWsj+c36KlS/vEm8d1uDEdZeQV2GO1+W8bqGO+VbXNYaUm1 EbI82Z1bSj9a82ekUUiOpHdOfPU27gLSgtauGooo= Date: Sun, 13 Mar 2022 16:16:44 +0200 From: Laurent Pinchart To: Sakari Ailus Cc: Paul Elder , Steve Longerbeam , Hans Verkuil , "Paul J. Murphy" , Martina Krasteva , Shawn Tu , Arec Kao , Kieran Bingham , Jimmy Su , Martin Kepplinger , Daniel Scally , Jacopo Mondi , Paul Kocialkowski , linux-media@vger.kernel.org Subject: Re: [PATCH v2] media: ov5640: Use runtime PM Message-ID: References: <20220311111259.3220718-1-paul.elder@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Sakari, On Sun, Mar 13, 2022 at 03:38:34PM +0200, Sakari Ailus wrote: > On Sun, Mar 13, 2022 at 03:01:52PM +0200, Laurent Pinchart wrote: > > On Fri, Mar 11, 2022 at 03:32:26PM +0200, Sakari Ailus wrote: > > > On Fri, Mar 11, 2022 at 03:20:55PM +0200, Laurent Pinchart wrote: > > > > On Fri, Mar 11, 2022 at 03:15:54PM +0200, Sakari Ailus wrote: > > > > > On Fri, Mar 11, 2022 at 02:30:09PM +0200, Laurent Pinchart wrote: > > > > > > On Fri, Mar 11, 2022 at 02:23:53PM +0200, Sakari Ailus wrote: > > > > > > > On Fri, Mar 11, 2022 at 08:12:59PM +0900, Paul Elder wrote: > > > > > > > > Switch to using runtime PM for power management. > > > > > > > > > > > > > > > > Signed-off-by: Paul Elder > > > > > > > > > > > > > > > > --- > > > > > > > > Changes in v2: > > > > > > > > - replace manual tracking of power status with pm_runtime_get_if_in_use > > > > > > > > - power on the sensor before reading the checking the chip id > > > > > > > > - add dependency on PM to Kconfig > > > > > > > > --- > > > > > > > > drivers/media/i2c/Kconfig | 1 + > > > > > > > > drivers/media/i2c/ov5640.c | 112 ++++++++++++++++++++++--------------- > > > > > > > > 2 files changed, 67 insertions(+), 46 deletions(-) > > > > > > > > > > > > > > > > diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig > > > > > > > > index e7194c1be4d2..97c3611d9304 100644 > > > > > > > > --- a/drivers/media/i2c/Kconfig > > > > > > > > +++ b/drivers/media/i2c/Kconfig > > > > > > > > @@ -1025,6 +1025,7 @@ config VIDEO_OV5640 > > > > > > > > tristate "OmniVision OV5640 sensor support" > > > > > > > > depends on OF > > > > > > > > depends on GPIOLIB && VIDEO_V4L2 && I2C > > > > > > > > + depends on PM > > > > > > > > > > > > > > I think this is not needed as the sensor is powered on explicitly in probe. > > > > > > > > > > > > > > You should similarly power it off explicitly in remove, set the runtime PM > > > > > > > status suspended and disable runtime PM. See e.g. imx319 driver for an > > > > > > > example. It doesn't have resume callback but that doesn't really matter --- > > > > > > > it's just ACPI-only. > > > > > > > > > > > > Do we want to continue supporting !PM ? Does it have any real use case > > > > > > when dealing with camera sensors ? > > > > > > > > > > Probably not much. > > > > > > > > > > The changes I proposed are not eve related on runtime PM. Hence the > > > > > question here is whether there should be a dependency to CONFIG_PM or not, > > > > > and as there's no technical reason to have it, it should be omitted. > > > > > > > > But if there's no real use case for !PM, wouldn't we be better off > > > > depending on PM and simplifying the probe functions instead ? > > > > > > What would change in the probe function if runtime PM was required by the > > > driver? > > > > We wouldn't need the complicated dance of calling > > > > ret = ov5640_set_power(sensor, true); > > if (ret) > > goto free_ctrls; > > > > pm_runtime_set_active(dev); > > pm_runtime_enable(dev); > > pm_runtime_get(dev); > > pm_runtime_get() is redundant here. > > > > > but could write it as > > > > pm_runtime_enable(dev); > > pm_runtime_resume_and_get(dev); > > You'll need put here, too. Yes, after reading the version register (or doing any other harware access). Actually the full code would be pm_runtime_enable(dev); pm_runtime_resume_and_get(dev); /* Hardware access */ pm_runtime_set_autosuspend_delay(dev, 1000); pm_runtime_use_autosuspend(dev); pm_runtime_put_autosuspend(dev); (plus error handling). If the probe function doesn't need to access the hardware, then the above becomes pm_runtime_enable(dev); pm_runtime_set_autosuspend_delay(dev, 1000); pm_runtime_use_autosuspend(dev); instead of having to power up the device just in case !PM. > Also the latter only works on DT-based systems so it's not an option for > most of the drivers. How so, what's wrong with the above for ACPI-based system ? -- Regards, Laurent Pinchart