On Fri, Mar 27, 2015 at 09:03:35AM +0100, Thomas Richter wrote: > Hi folks, hi Daniel, hi Ville, > > thanks again for getting my old Laptops (the R31 and the S6010) back to > life. It's been quite a way, but everything looks fine now. > > There is one interesting observation I made, though, on my IBM R31 > laptop: The i830GM graphics supports 24bpp pipes, thought the panel is > only a 6-bit panel, i.e. 18bpp. As you say, the i830GM does not support > dithering, but interestingly, as I found out by accident, the iVCH DVO > chip in the laptop does. If you press FN+F8 (usually to control the > scaling of the display per bios), the image quality improves > dramatically, apparently by reconfiguring the settings of the iVCH > bypassing the kernel. This is handled by the Bios. > > Now, I would like to find the settings the Bios leaves in the iVCH. > Unfortunately, there is a catch here: According to the kernel sources, > the iVCH is connected to the i2c-bus, but at address #2. My knowledge of > i2c is limited, but from what I know, this is actually not a valid > address and is rather used for some control mechanism of i2c itself. > Hence, the usual i2c tools do not allow me to reach out for the chip and > read its registers. > > Question: > > How can possibly read out the settings of the i2c chip with system > tools? I know the kernel does a register dump of what it installs during > DVO initialization, and have these values, but what I don't have are the > values the bios leaves when I press FN+F8. i2c uses 7 bits for address and bit 8 for read/write indication. There's a bit confusion between tools and kernel about whether to include the read/write bit or not, so maybe try with 1 instead? Plan b would be to extend the ivch_dump_regs and wire that up into a debugfs file. Then you could dump the registers through the kernel before/after pressing the magic key. but tbh I don't have much i2c clue either. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
