Hi Tomasz, On Fri, Oct 12, 2018 at 01:51:10PM +0900, Tomasz Figa wrote: > Hi Sakari, > > On Wed, Sep 26, 2018 at 11:38 AM <bingbu.cao@xxxxxxxxx> wrote: > > > > From: Bingbu Cao <bingbu.cao@xxxxxxxxx> > > > > Add a v4l2 sub-device driver for the Sony imx319 image sensor. > > This is a camera sensor using the i2c bus for control and the > > csi-2 bus for data. > > > > This driver supports following features: > > - manual exposure and analog/digital gain control support > > - vblank/hblank control support > > - 4 test patterns control support > > - vflip/hflip control support (will impact the output bayer order) > > - support following resolutions: > > - 3264x2448, 3280x2464 @ 30fps > > - 1936x1096, 1920x1080 @ 60fps > > - 1640x1232, 1640x922, 1296x736, 1280x720 @ 120fps > > - support 4 bayer orders output (via change v/hflip) > > - SRGGB10(default), SGRBG10, SGBRG10, SBGGR10 > > > > Cc: Tomasz Figa <tfiga@xxxxxxxxxxxx> > > Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > > Signed-off-by: Bingbu Cao <bingbu.cao@xxxxxxxxx> > > Signed-off-by: Tianshu Qiu <tian.shu.qiu@xxxxxxxxx> > > > > --- > > > > This patch is based on sakari's media-tree git: > > https://git.linuxtv.org/sailus/media_tree.git/log/?h=for-4.20-1 > > > > Changes from v5: > > - add some comments for gain calculation > > - use lock to protect the format > > - fix some style issues > > > > Changes from v4 to v5: > > - use single PLL for all internal clocks > > - change link frequency to 482.4MHz > > - adjust frame timing for 2x2 binning modes > > and enlarge frame readout time > > - get CSI-2 link frequencies and external clock > > from firmware > > If I remember correctly, that was suggested by you. Why do we need to > specify link frequency in firmware if it's fully configured by the > driver, with the only external dependency being the external clock? The driver that's now in upstream supports, for now, a very limited set of configurations from what the sensor supports. These are more or less tailored to the particular system where it is being used right now (output image size, external clock frequency, frame rates, link frequencies etc.). If the same sensor is needed elsewhere (quite likely), the configuration needed elsewhere is very likely to be different from what you're using now. The link frequency in particular is important as using a different link frequency (which could be fine elsewhere) could cause EMI issues, e.g. rendering your GPS receiver inoperable during the time the camera sensor is streaming images. Should new configurations be added to this driver to support a different system, the link frequencies used by those configurations may be problematic to your system, and after a software update the driver could as well use those new frequencies. That's a big no-no. > > We're having problems with firmware listing the link frequency from v4 > and we can't easily change it anymore to report the new one. I feel > like this dependency on the firmware here is unnecessary, as long as > the external clock frequency matches. This is information you really need to know. A number of older drivers do not use the link frequency information from the firmware but that comes with a risk. Really, it's better to change the frequency now to something you can choose, rather than have it changed later on to something someone else chose for you. -- Kind regards, Sakari Ailus sakari.ailus@xxxxxxxxxxxxxxx
