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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A75F4C433E6 for ; Mon, 22 Feb 2021 02:08:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 738C564F06 for ; Mon, 22 Feb 2021 02:08:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231759AbhBVCIH (ORCPT ); Sun, 21 Feb 2021 21:08:07 -0500 Received: from perceval.ideasonboard.com ([213.167.242.64]:55074 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231510AbhBVCIG (ORCPT ); Sun, 21 Feb 2021 21:08:06 -0500 Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 5AE13517; Mon, 22 Feb 2021 03:07:20 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1613959640; bh=N3aMmfIUEadOI2Iioow3EmeF/Ng+HvjdFDJWbVjH194=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=wH/02blkfOHdWMcl1C5m7/PZWF8vIVCrvEFxlF3P+ll3s7E0bnLEHpQN3SqB+LNa5 rmscB6c8/B4XmfI4N5lBOVNDIJFqTjgZifk5y91EBN2zE159r0J8qn0aB60B1eb7DL jm4no49nUlkkFR4Kt9FGhwYp1DnzGa2Q18NrPOMQ= Date: Mon, 22 Feb 2021 04:06:48 +0200 From: Laurent Pinchart To: Jacopo Mondi Cc: Kieran Bingham , 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 Subject: Re: [PATCH 16/16] media: i2c: gmsl: Use 339Kbps I2C bit-rate Message-ID: References: <20210216174146.106639-1-jacopo+renesas@jmondi.org> <20210216174146.106639-17-jacopo+renesas@jmondi.org> 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 Jacopo, Thank you for the patch. On Thu, Feb 18, 2021 at 04:07:30PM +0000, Kieran Bingham wrote: > On 16/02/2021 17:41, Jacopo Mondi wrote: > > With the camera modules initialization routines now running with > > the noise immunity threshold enabled, it is possible to restore > > the bit rate of the I2C transactions transported on the GMSL control > > channel to 339 Kbps. > > > > The 339 Kbps bit rate represents the default setting for the serializer > > and the deserializer chips, and the setup/hold time and slave timeout > > time in use are calibrate to support that rate. > > s/calibrate/calibrated/ > > Does that mean the setup/hold time and timeouts should be adjusted based > on the i2c speed? (which we have not been doing?) > > With all of your other reliability improvements, does *this* change > alone have any difference or impact on reliability? > > I.e. if we go slower (stay at current speed) - would we be more reliable? > > Is there a reliability improvement by making this speed faster? > > I presume we don't have a way to convey the i2c bus speed between the > max9286 and the max9271 currently? Seems a bit like a bus parameter.... There's a max bus speed DT parameter that we can use. And I think we should, as, in theory at least, there's no guarantee that all the devices behind the serializer can operate at 400kbps. > > Signed-off-by: Jacopo Mondi > > --- > > drivers/media/i2c/max9286.c | 2 +- > > drivers/media/i2c/rdacm20.c | 2 +- > > drivers/media/i2c/rdacm21.c | 2 +- > > 3 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c > > index aa01d5bb79ef..0b620f2f8c41 100644 > > --- a/drivers/media/i2c/max9286.c > > +++ b/drivers/media/i2c/max9286.c > > @@ -330,7 +330,7 @@ static int max9286_i2c_mux_init(struct max9286_priv *priv) > > static void max9286_configure_i2c(struct max9286_priv *priv, bool localack) > > { > > u8 config = MAX9286_I2CSLVSH_469NS_234NS | MAX9286_I2CSLVTO_1024US | > > - MAX9286_I2CMSTBT_105KBPS; > > + MAX9286_I2CMSTBT_339KBPS; > > > > if (localack) > > config |= MAX9286_I2CLOCACK; > > diff --git a/drivers/media/i2c/rdacm20.c b/drivers/media/i2c/rdacm20.c > > index 0632ef98eea7..d45e8b0e52a0 100644 > > --- a/drivers/media/i2c/rdacm20.c > > +++ b/drivers/media/i2c/rdacm20.c > > @@ -450,7 +450,7 @@ static int rdacm20_init(struct v4l2_subdev *sd, unsigned int val) > > ret = max9271_configure_i2c(&dev->serializer, > > MAX9271_I2CSLVSH_469NS_234NS | > > MAX9271_I2CSLVTO_1024US | > > - MAX9271_I2CMSTBT_105KBPS); > > + MAX9271_I2CMSTBT_339KBPS); > > if (ret) > > return ret; > > > > diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c > > index 80b6f16f87a8..552985026458 100644 > > --- a/drivers/media/i2c/rdacm21.c > > +++ b/drivers/media/i2c/rdacm21.c > > @@ -442,7 +442,7 @@ static int rdacm21_init(struct v4l2_subdev *sd, unsigned int val) > > ret = max9271_configure_i2c(&dev->serializer, > > MAX9271_I2CSLVSH_469NS_234NS | > > MAX9271_I2CSLVTO_1024US | > > - MAX9271_I2CMSTBT_105KBPS); > > + MAX9271_I2CMSTBT_339KBPS); > > if (ret) > > return ret; > > -- Regards, Laurent Pinchart