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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4065C43461 for ; Thu, 15 Apr 2021 12:31:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A2A7F6044F for ; Thu, 15 Apr 2021 12:31:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232869AbhDOMbx (ORCPT ); Thu, 15 Apr 2021 08:31:53 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:60479 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231482AbhDOMbt (ORCPT ); Thu, 15 Apr 2021 08:31:49 -0400 X-Originating-IP: 93.61.96.190 Received: from uno.localdomain (93-61-96-190.ip145.fastwebnet.it [93.61.96.190]) (Authenticated sender: jacopo@jmondi.org) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id 3ED4B60009; Thu, 15 Apr 2021 12:31:19 +0000 (UTC) Date: Thu, 15 Apr 2021 14:31:59 +0200 From: Jacopo Mondi To: Jacopo Mondi Cc: kieran.bingham+renesas@ideasonboard.com, laurent.pinchart+renesas@ideasonboard.com, niklas.soderlund+renesas@ragnatech.se, geert@linux-m68k.org, Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Sakari Ailus , Hans Verkuil Subject: Re: [PATCH v4 16/17] media: v4l2-subdev: De-deprecate init() subdev op Message-ID: <20210415123159.oh3hurafvimgzgt6@uno.localdomain> References: <20210412093451.14198-1-jacopo+renesas@jmondi.org> <20210412093451.14198-17-jacopo+renesas@jmondi.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210412093451.14198-17-jacopo+renesas@jmondi.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, with feedback from media maintainers I can resend the series which is now fully reviewed. Thanks j On Mon, Apr 12, 2021 at 11:34:50AM +0200, Jacopo Mondi wrote: > The init() subdev core operation is deemed to be deprecated for new > subdevice drivers. However it could prove useful for complex > architectures to defer operation that require access to the > communication bus if said bus is not available (or fully configured) > at the time when the subdevice probe() function is run. > > As an example, the GMSL architecture requires the GMSL configuration > link to be configured on the host side after the remote subdevice > has completed its probe function. After the configuration on the host > side has been performed, the subdevice registers can be accessed through > the communication bus. > > In particular: > > HOST REMOTE > > probe() > | > ---------------------> | > probe() { > bus config() > } > |<--------------------| > v4l2 async bound { > bus config() > call subdev init() > |-------------------->| > init() { > access register on the bus() > } > |<------------------- > } > > In the GMSL use case the bus configuration requires the enablement of the > noise immunity threshold on the remote side which ensures reliability > of communications in electrically noisy environments. After the subdevice > has enabled the threshold at the end of its probe() sequence the host > side shall compensate it with an higher signal amplitude. Once this > sequence has completed the bus can be accessed with noise protection > enabled and all the operations that require a considerable number of > transactions on the bus (such as the image sensor configuration > sequence) are run in the subdevice init() operation implementation. > > Signed-off-by: Jacopo Mondi > --- > include/media/v4l2-subdev.h | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h > index d0e9a5bdb08b..3068d9940669 100644 > --- a/include/media/v4l2-subdev.h > +++ b/include/media/v4l2-subdev.h > @@ -148,9 +148,18 @@ struct v4l2_subdev_io_pin_config { > * each pin being configured. This function could be called at times > * other than just subdevice initialization. > * > - * @init: initialize the sensor registers to some sort of reasonable default > - * values. Do not use for new drivers and should be removed in existing > - * drivers. > + * @init: initialize the subdevice registers to some sort of reasonable default > + * values. Do not use for new drivers (and should be removed in existing > + * ones) for regular architectures where the image sensor is connected to > + * the host receiver. For more complex architectures where the subdevice > + * initialization should be deferred to the completion of the probe > + * sequence of some intermediate component, or the communication bus > + * requires configurations on the host side that depend on the completion > + * of the probe sequence of the remote subdevices, the usage of this > + * operation could be considered to allow the devices along the pipeline to > + * probe and register in the media graph and to defer any operation that > + * require actual access to the communication bus to their init() function > + * implementation. > * > * @load_fw: load firmware. > * > -- > 2.31.1 >