Hello Hyun, Kieran, it's great you are looking into this! On Fri, Feb 28, 2020 at 10:13:04AM -0800, Hyun Kwon wrote: > Hi Kieran, > > Thanks for sharing a patch. > [snip] > > > + > > > + /* > > > + * Set the I2C bus speed. > > > + * > > > + * Enable I2C Local Acknowledge during the probe sequences of the camera > > > + * only. This should be disabled after the mux is initialised. > > > + */ > > > + max9286_configure_i2c(priv, true); > > > + > > > + /* > > > + * Reverse channel setup. > > > + * > > > + * - Enable custom reverse channel configuration (through register 0x3f) > > > + * and set the first pulse length to 35 clock cycles. > > > + * - Increase the reverse channel amplitude to 170mV to accommodate the > > > + * high threshold enabled by the serializer driver. > > > + */ > > > + max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35)); > > > + max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) | > > > + MAX9286_REV_AMP_X); > > > + usleep_range(2000, 2500); > > > + > > > + /* > > > + * Enable GMSL links, mask unused ones and autodetect link > > > + * used as CSI clock source. > > > + */ > > > + max9286_write(priv, 0x00, MAX9286_MSTLINKSEL_AUTO | priv->route_mask); > > > + max9286_write(priv, 0x0b, link_order[priv->route_mask]); > > > + max9286_write(priv, 0x69, (0xf & ~priv->route_mask)); > > > + > > > + /* > > > + * Video format setup: > > > + * Disable CSI output, VC is set according to Link number. > > > + */ > > > + max9286_write(priv, 0x15, MAX9286_VCTYPE | MAX9286_0X15_RESV); > > > + > > > + /* Enable CSI-2 Lane D0-D3 only, DBL mode, YUV422 8-bit. */ > > > + max9286_write(priv, 0x12, MAX9286_CSIDBL | MAX9286_DBL | > > > + MAX9286_CSILANECNT(priv->csi2_data_lanes) | > > > + MAX9286_DATATYPE_YUV422_8BIT); > > > + > > > + /* Automatic: FRAMESYNC taken from the slowest Link. */ > > > + max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_HIZ | > > > + MAX9286_FSYNCMETH_AUTO); > > > + > > > + /* Enable HS/VS encoding, use D14/15 for HS/VS, invert VS. */ > > > + max9286_write(priv, 0x0c, MAX9286_HVEN | MAX9286_INVVS | > > > + MAX9286_HVSRC_D14); > I agree we need to make some of these configurable, we need that too to handle both rdacm20 and 21. > Some of these configs in fact need some handshake between serializer and > de-serializer. For example, I had to invert vsync in serializer [3] to make > it work with this patch. Quickly skamming through the datasheet I'm surprised there is no way to control the vsync input polarity and you have to go through the crossbar :) Oh well, I think this could be well controlled through a device property of the serializer, what do you think? We have standard properties to control vsync and hsync polarities, but they're usually used for output signals, and I would reserve them for that future usage.. maybe a custom property to control the input vsync and hsync polarities would do... > > In addition to that, I need a couple of additional programmings on max9286 > (registers 0x0 to 0x63/0x64- disable overlap window and 0xf4 to 0x1c which > oddly change reserved bits) to get frames. The datasheet doesn't explain > enough for me to understand. I'm talking to Maxim to get more details and > see if those can be handled by serilizer driver. I would be really interested in knowing what's the overlap window control about... it's very little detailed in the manual, I agree :) 0xf4 is not even documented in my version. I assume it's something related to fsync sync locking (Fig. 46) as I failed to achieve it without that setting. How did it fail for you ? On how to control overlap window a integer would do ? Setting it to 0 disables it, so we could use a boolean property for convenience.. Not knowing what it does I would be careful.. I think we should actualy require a mandatory property, so all current dts select their behaviour explicitly. If we later find out what it does we could define a default behaviour by defining a boolean property. New dts simpler and old dts still happy. What do you think ? > > In a longer term, it'd be nice if such alignment between serializer and > de-serializer is handled in more scalable way. > Indeed :) Thanks j > Thanks, > -hyun > > [1] https://github.com/xlnx-hyunkwon/linux-xlnx/commit/3bd2dded834492f4ee89e370c22877b97c2e106e > [2] https://github.com/xlnx-hyunkwon/linux-xlnx/commit/fb0ad7fd699d90d6bbc78fc55dd98639389cfc5b > [3] https://github.com/xlnx-hyunkwon/linux-xlnx/commit/fe0b33b174b2850bf0bb25b3a367319127ae12ee >
