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Open Source and information security mailing list archives
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Date: Fri, 17 Feb 2017 12:38:20 +0100 From: Philipp Zabel <p.zabel@...gutronix.de> To: Russell King - ARM Linux <linux@...linux.org.uk> Cc: Steve Longerbeam <slongerbeam@...il.com>, robh+dt@...nel.org, mark.rutland@....com, shawnguo@...nel.org, kernel@...gutronix.de, fabio.estevam@....com, mchehab@...nel.org, hverkuil@...all.nl, nick@...anahar.org, markus.heiser@...marIT.de, laurent.pinchart+renesas@...asonboard.com, bparrot@...com, geert@...ux-m68k.org, arnd@...db.de, sudipm.mukherjee@...il.com, minghsiu.tsai@...iatek.com, tiffany.lin@...iatek.com, jean-christophe.trotin@...com, horms+renesas@...ge.net.au, niklas.soderlund+renesas@...natech.se, robert.jarzmik@...e.fr, songjun.wu@...rochip.com, andrew-ct.chen@...iatek.com, gregkh@...uxfoundation.org, shuah@...nel.org, sakari.ailus@...ux.intel.com, pavel@....cz, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org, devel@...verdev.osuosl.org, Steve Longerbeam <steve_longerbeam@...tor.com> Subject: Re: [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev driver On Fri, 2017-02-17 at 11:06 +0000, 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. I had code to calculate the number of needed lanes from the bit rate and link frequency. I did not actually change the D-PHY register value. And as you pointed out, calculating the number of lanes is not useful without input from the sensor driver, as some lane configurations might not be supported. > 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.) The tc358743 also currently only implements a fixed rate (of 594 Mbps). regards Philipp
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