Hi Tomasz, On Thu, Oct 18, 2018 at 12:24:31PM +0900, Tomasz Figa wrote: > On Tue, Oct 16, 2018 at 8:50 PM Sakari Ailus > <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > > > > Hi Tomasz, > > > > On Fri, Oct 12, 2018 at 05:06:56PM +0900, Tomasz Figa wrote: > > > On Fri, Oct 12, 2018 at 4:58 PM Sakari Ailus > > > <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > > > > > > > > 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.). > > > > > > As a side note, they're tailored to exactly the system I mentioned, > > > with different link frequency hardcoded in the firmware, coming from > > > earlier stage of development. > > > > > > > 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. > > > > > > > > > > Okay, those are some valid points indeed, thanks for clarifying. > > > > > > > > > > > > > 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. > > > > > > I guess it means that we have to carry a local downstream patch that > > > bypasses this check, since we cannot easily change the firmware > > > anymore. > > > > Is there a possibility update the firmware, or carry an SSDT overlay as part > > of the software? The options are laid out in > > Documentation/acpi/ssdt-overlays.txt . Do remember to pay attention to the > > revision field --- also in future Coreboot updates. > > > > Generally we try to avoid updating the firmware in the field, but most > of the time there is a reason to do it anyway, so that might > eventually happen. Let me try to figure out. > > > > > > > An alternative would be to make the driver try to select a frequency > > > that matches what's in the firmware, but issue a warning and fall back > > > to a default one if a matching is not found. It might be actually > > > better than nothing for some early testing on new systems, since it > > > wouldn't require firmware changes. > > > > You don't need firmware changes per se; see above. Allowing that will very, > > very easily lead this being unaddressed during developement and changing > > later on inadvertly. > > Still, requiring the user to create an SSDT overlay sounds like an > overkill, for something that is not really a fatal error. We handle > ACPI firmware bugs in many parts of the kernel by issuing a warning > and using some reasonably safe fallback and I don't know why we > couldn't do the same here. To address this in kernel only, I presume one would have to plant that snippet in the ACPI table based on recognising the machine name and the firmware version. I don't think this is supported right now. OTOH, an alternative option could be, if you use initrd for other reasons, to bake the SSDT overlay into the initrd based on the machine identification when creating the initrd image. That would require no kernel changes and compared to making kernel changes, this way also there would be no adverse effect on the size of the kernel. -- Regards, Sakari Ailus sakari.ailus@xxxxxxxxxxxxxxx
