From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pg0-f65.google.com ([74.125.83.65]:35486 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933767AbdBWAGk (ORCPT ); Wed, 22 Feb 2017 19:06:40 -0500 Subject: Re: [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev driver To: Russell King - ARM Linux , Philipp Zabel References: <1487211578-11360-1-git-send-email-steve_longerbeam@mentor.com> <1487211578-11360-24-git-send-email-steve_longerbeam@mentor.com> <1487328479.3107.21.camel@pengutronix.de> <20170217110616.GD21222@n2100.armlinux.org.uk> Cc: robh+dt@kernel.org, mark.rutland@arm.com, shawnguo@kernel.org, kernel@pengutronix.de, fabio.estevam@nxp.com, mchehab@kernel.org, hverkuil@xs4all.nl, nick@shmanahar.org, markus.heiser@darmarIT.de, laurent.pinchart+renesas@ideasonboard.com, bparrot@ti.com, geert@linux-m68k.org, arnd@arndb.de, sudipm.mukherjee@gmail.com, minghsiu.tsai@mediatek.com, tiffany.lin@mediatek.com, jean-christophe.trotin@st.com, horms+renesas@verge.net.au, niklas.soderlund+renesas@ragnatech.se, robert.jarzmik@free.fr, songjun.wu@microchip.com, andrew-ct.chen@mediatek.com, gregkh@linuxfoundation.org, shuah@kernel.org, sakari.ailus@linux.intel.com, pavel@ucw.cz, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, devel@driverdev.osuosl.org, Steve Longerbeam From: Steve Longerbeam Message-ID: <20b7d3b7-85be-b701-19ca-1e8024260fc2@gmail.com> Date: Wed, 22 Feb 2017 16:06:36 -0800 MIME-Version: 1.0 In-Reply-To: <20170217110616.GD21222@n2100.armlinux.org.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 02/17/2017 03:06 AM, Russell King - ARM Linux wrote: > On Fri, Feb 17, 2017 at 11:47:59AM +0100, Philipp Zabel wrote: >> On Wed, 2017-02-15 at 18:19 -0800, Steve Longerbeam wrote: >>> +static void csi2_dphy_init(struct csi2_dev *csi2) >>> +{ >>> + /* >>> + * FIXME: 0x14 is derived from a fixed D-PHY reference >>> + * clock from the HSI_TX PLL, and a fixed target lane max >>> + * bandwidth of 300 Mbps. This value should be derived >> >> If the table in https://community.nxp.com/docs/DOC-94312 is correct, >> this should be 850 Mbps. Where does this 300 Mbps value come from? > > I thought you had some code to compute the correct value, although > I guess we've lost the ability to know how fast the sensor is going > to drive the link. > > Note that the IMX219 currently drives the data lanes at 912Mbps almost > exclusively, as I've yet to finish working out how to derive the PLL > parameters. (I have something that works, but it currently takes on > the order of 100k iterations to derive the parameters. gcd() doesn't > help you in this instance.) Hi Russell, As I mentioned, I've added code to imx6-mipi-csi2 to determine the sources link frequency via V4L2_CID_LINK_FREQ. If you were to implement this control and return 912 Mbps-per-lane, the D-PHY will be programmed correctly for the IMX219 (at least, that is the theory anyway). Alternatively, I could up the default in imx6-mipi-csi2 to 950 Mbps. I will have to test that to make sure it still works with OV5640 and tc358743. Steve