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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 733B4C4332D for ; Wed, 18 Mar 2020 23:22:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 474FA2076E for ; Wed, 18 Mar 2020 23:22:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="oE6t/vXk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727236AbgCRXWo (ORCPT ); Wed, 18 Mar 2020 19:22:44 -0400 Received: from perceval.ideasonboard.com ([213.167.242.64]:42586 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726619AbgCRXWo (ORCPT ); Wed, 18 Mar 2020 19:22:44 -0400 Received: from pendragon.ideasonboard.com (81-175-216-236.bb.dnainternet.fi [81.175.216.236]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 97FC55F; Thu, 19 Mar 2020 00:22:41 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1584573761; bh=1QAaixOPnCwRw0nvHVWpdyGWaxWNnlcsHJ49Rt5k58U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oE6t/vXko3yx5XAp9J589i8nmC888tp0v4tRNpiAWr96RdlwpAmyPgSnKB6ylZ3Ed KCyszDJ5PVG8nNuo9n3ParRafUZPjU/cytzUaXu726C2RtCCbBFPU/TxL+ESM52ohX G6UZkWgj7t41IP17PvvPQAychsPHRSDWPCPYrEyI= Date: Thu, 19 Mar 2020 01:22:36 +0200 From: Laurent Pinchart To: "Lad, Prabhakar" Cc: Mark Rutland , "devicetree@vger.kernel.org" , Fabio Estevam , Sakari Ailus , Ezequiel Garcia , Prabhakar Mahadev Lad , Sascha Hauer , Magnus Damm , "linux-kernel@vger.kernel.org" , "linux-renesas-soc@vger.kernel.org" , Rob Herring , Geert Uytterhoeven , NXP Linux Team , Pengutronix Kernel Team , Mauro Carvalho Chehab , Shawn Guo , "linux-arm-kernel@lists.infradead.org" , "linux-media@vger.kernel.org" Subject: Re: [PATCH v3 3/4] media: i2c: ov5645: Set maximum leverage of external clock frequency to 24480000 Message-ID: <20200318232236.GJ24538@pendragon.ideasonboard.com> References: <1584133954-6953-1-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com> <1584133954-6953-4-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com> <20200313212345.GM4751@pendragon.ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Prabhakar, On Wed, Mar 18, 2020 at 10:41:57PM +0000, Lad, Prabhakar wrote: > On Fri, Mar 13, 2020 at 9:31 PM Prabhakar Mahadev Lad wrote: > > On 13 March 2020 21:24, Laurent Pinchart wrote: > >> On Fri, Mar 13, 2020 at 09:12:33PM +0000, Lad Prabhakar wrote: > >>> While testing on Renesas RZ/G2E platform, noticed the clock frequency > >>> to be 24242424 as a result the probe failed. However increasing the > >>> maximum leverage of external clock frequency to 24480000 fixes this > >>> issue. Since this difference is small enough and is insignificant set > >>> the same in the driver. > >>> > >>> Signed-off-by: Lad Prabhakar > >>> --- > >>> drivers/media/i2c/ov5645.c | 6 ++++-- > >>> 1 file changed, 4 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/media/i2c/ov5645.c b/drivers/media/i2c/ov5645.c > >>> index 4fbabf3..b49359b 100644 > >>> --- a/drivers/media/i2c/ov5645.c > >>> +++ b/drivers/media/i2c/ov5645.c > >>> @@ -1107,8 +1107,10 @@ static int ov5645_probe(struct i2c_client *client) > >>> } > >>> > >>> xclk_freq = clk_get_rate(ov5645->xclk); > >>> -/* external clock must be 24MHz, allow 1% tolerance */ > >>> -if (xclk_freq < 23760000 || xclk_freq > 24240000) { > >>> +/* external clock must be 24MHz, allow a minimum 1% and a > >> maximum of 2% > >>> + * tolerance > >> > >> So where do these numbers come from ? I understand that 2% is what you > >> need to make your clock fit in the range, but why -1%/+2% instead of - > >> 2%/+2% ? And why not 2.5 or 3% ? The sensor datasheet documents the > >> range of supported xvclk frequencies to be 6MHz to 54MHz. I understand > >> that PLL parameters depend on the clock frequency, but could they be > >> calculated instead of hardcoded, to avoid requiring an exact 24MHz input > >> frequency ? > >> > > To be honest I don't have the datasheet for ov5645, the flyer says 6-54Mhz but the > > logs/comment says 24Mhz. > > > Comparing to ov5640 datasheet [1] (which I am assuming might be > similar to ov5645), Let's assume this to be the case, I see no reason not to :-) > this change should affect the driver. How do you mean ? > [1] https://cdn.sparkfun.com/datasheets/Sensors/LightImaging/OV5640_datasheet.pdf > > >>> + */ > >>> +if (xclk_freq < 23760000 || xclk_freq > 24480000) { > >>> dev_err(dev, "external clock frequency %u is not supported\n", > >>> xclk_freq); > >>> return -EINVAL; -- Regards, Laurent Pinchart