Messages in this thread | | | Subject | Re: [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev driver | From | Steve Longerbeam <> | Date | Wed, 22 Feb 2017 16:06:36 -0800 |
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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
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