From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Longerbeam Subject: Re: [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev driver Date: Wed, 22 Feb 2017 16:09:23 -0800 Message-ID: <80ecf2ef-8e52-0c60-87b5-8325571857ee@gmail.com> 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> <20b7d3b7-85be-b701-19ca-1e8024260fc2@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20b7d3b7-85be-b701-19ca-1e8024260fc2@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" To: Russell King - ARM Linux , Philipp Zabel Cc: mark.rutland@arm.com, andrew-ct.chen@mediatek.com, minghsiu.tsai@mediatek.com, nick@shmanahar.org, songjun.wu@microchip.com, hverkuil@xs4all.nl, Steve Longerbeam , pavel@ucw.cz, robert.jarzmik@free.fr, devel@driverdev.osuosl.org, markus.heiser@darmarIT.de, laurent.pinchart+renesas@ideasonboard.com, shuah@kernel.org, geert@linux-m68k.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, sakari.ailus@linux.intel.com, arnd@arndb.de, mchehab@kernel.org, bparrot@ti.com, robh+dt@kernel.org, horms+renesas@verge.net.au, tiffany.lin@mediatek.com, linux-arm-kernel@lists.infradead.org, niklas.soderlund+renesas@ragnatech.se, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, jean-christophe.trotin@st.com, kernel@pengutronix.de, fabio.estevam@nxp.com, shawnguo@kernel.org, sudipm.mukherjee@gmail.com List-Id: devicetree@vger.kernel.org On 02/22/2017 04:06 PM, Steve Longerbeam wrote: > > > 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, argh, I mean return 912 / 2. Steve 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