-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 BLC_PWM_CTL is in src/mainboard/lenovo/x60/devicetree.cb, see gpu_brightness or gpu_backlight or something like that. You can change the value there.
On 06/04/15 05:54, Charles Devereaux wrote: > Hello > > On my X60 tablet, after a screen swap for a 1400x1050 screen, I > started noticing a whine. The noise is proportional to the > reduction of the backlight and doesn't happen at full brightness. I > never noticed it before. > > It happens regardless of how I change the backlight (fn+home/end, > xbacklight, custom script reading and writing to > /sys/class/backlight/intel_backlight/brightness) so I suspect a > coreboot issue. > > I am currently using an old libreboot based on head > 8ffc085e1affaabbe3dca8ac6a89346b71dfc02e with #5345, #7050, #7051, > but not #6731 and #7049 (since they were dropped and I do not need > acpi backlight) that works just fine, so I am a bit reluctant to > change it. > > Apparently #6731 and #7049 had the same problem: "some lower > brightness levels make the high-pitched noise", which was fixed cf > http://review.coreboot.org/#/c/6731/ > > After looking at the code, I see a note explaining how: "Francis > tested that like my noise issue it doesn't occur with a lower PWM > frequency. > > If we compute the frequency as (0x61 << 8) + (0x61 << 6) + 1 (the 1 > is to allow legacy backlight brightness which the VGA ROM allows > and I don't know if it should be enabled) and duty cycle as (x << > 8) + (x << 6) for x in 0xf, ..., 0x61, then both our issues are > solved. > > I don't know if the resulting value (0x79417940) gives low enough > frequency to cause flickering for other users: " > > I do not fully understand where or how the PWM frequency is set in > src/northbridge/intel/i945/gma.c. I never see that 0x79417940 > either. the only thing I see in > http://review.coreboot.org/#/c/6731/7/src/northbridge/intel/i945/gma.c > is: > > write32(pmmio + BLC_PWM_CTL, 0x6100610); > > In the source of my libreboot, it is still: > > write32(pmmio + BLC_PWM_CTL, conf->gpu_backlight); > > With src/mainboard/lenovo/x60/devicetree.cb setting it with: > > register "gpu_backlight" = "0x879F879E" > > Should it get changed to: > > write32(pmmio + BLC_PWM_CTL, 0x79417940) The other thing I noticed > were kernel warnings on wakeup from suspend2ram: [54557.710112] > [drm:intel_pipe_config_compare] *ERROR* mismatch in > gmch_pfit.pgm_ratios (expected 24183152, found 24117616) > [54557.710114] ------------[ cut here ]------------ [54557.710121] > WARNING: CPU: 1 PID: 1432 at > drivers/gpu/drm/i915/intel_display.c:9541 > check_crtc_state+0x759/0xe31() [54557.710122] pipe state doesn't > match! > > It may be related. Which coreboot head/patches is libreboot on the > X60 presently using? > > Thanks Charles > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJVIh6qAAoJEP9Ft0z50c+UUCEIALbSvFrymaYCKs9d7YTnR5NC vJkvDNZ5NknB5Q8LjcQuhf9RQ+KMVgxF28sLWL7Bc9ikHgZvH1jH5ykAn7x4rBjO AUp2l+7NrUnziEllJDQPkfQksy45yMr/c8qZgBm+yeIEPAkM3zRc4k5LNhqmlaPI AhrUG1sFLt7EAvXqgnlq5jNr/8ogZh9A7Q4I2sWka4UmVj+VhZnG0XNu5a94GqYe HTyu0OgOYTiPwOQiVyzGPeN+dGYiz86aHyi49uv1nRlaowk8hNXa19prXuf6fVQV cczdPfs5CMFYBlGKjKz3lq2eg6ARKnuQVCH4wq0HaR0ztbUABwwY3UpWEd3FyJc= =1AmA -----END PGP SIGNATURE-----
