Hi, On 10/27/21 15:38, Ville Syrjälä wrote: > On Sun, Oct 24, 2021 at 05:50:10PM +0200, Hans de Goede wrote: >> Add a NO_VLV_DISP_PW_DPIO_CMN_BC_INIT quirk to fix i915 not working on >> the Xiaomi Mi Pad 2 (with CHT x5-Z8500 SoC). >> >> The Xiaomi Mi Pad 2 uses quite an unusual hardware-design for a Cherry >> Trail tablet. It deviates from the typical reference design based tablets >> in many ways. >> >> The Mi Pad 2 does not have any DisplayPort or HDMI outouts. I suspect that >> as part of its unusual design it also has some supply rail which is only >> used for DisplayPort or HDMI not connected. > > Do we have the VBT somewhere (preferable attached to a bug report)? > Maybe we can avoid an ugly quirk. I agree that solving this in a way where we can avoid the quirk would be great. I've filed an issue for this here now: https://gitlab.freedesktop.org/drm/intel/-/issues/4385 This has a dump of /sys/kernel/debug/dri/0/i915_vbt as well as dmesg output from a boot with drm.debug=0x1e attached (from a boot with this patch, since otherwise the system hangs). >> >> Force-enabling the dpio-common-bc powerwell as the i915 normal does at boot >> appears to cause the P-Unit to hang. When booting with a serial-usb console >> the following errors are logged before the system freezes: >> >> i915 0000:00:02.0: [drm] *ERROR* timeout setting power well state 00000000 (fffff3ff) >> i915 0000:00:02.0: [drm] *ERROR* Display PHY 0 is not power up > > Hmm. I wonder if we're missing a clock or something... > > Either of these do anything different? > > --- a/drivers/gpu/drm/i915/display/intel_display_power.c > +++ b/drivers/gpu/drm/i915/display/intel_display_power.c > @@ -1419,6 +1419,10 @@ static void vlv_display_power_well_init(struct drm_i915_private *dev_priv) > for_each_pipe(dev_priv, pipe) { > u32 val = intel_de_read(dev_priv, DPLL(pipe)); > > + val |= DPLL_SSC_REF_CLK_CHV; > or > + val &= ~DPLL_SSC_REF_CLK_CHV; > > val |= DPLL_REF_CLK_ENABLE_VLV | DPLL_VGA_MODE_DIS; > if (pipe != PIPE_A) > val |= DPLL_INTEGRATED_CRI_CLK_VLV; > The hang gets triggered from chv_dpio_cmn_power_well_enable() which does not call vlv_display_power_well_init() at all, it directly calls vlv_set_power_well() without first calling vlv_display_power_well_init() . Note the same goes for vlv_dpio_cmn_power_well_enable(). Only the vlv_display_power_well_enable() / chv_pipe_power_well_enable() call vlv_display_power_well_init(). Note I can still give the suggested change a try if you want, the "display" powerwell is listed first and has DOMAIN_INIT set, so assuming for_each_power_domain_well() goes through the domains in the order they are listed, then vlv_display_power_well_init() will still run first. But it would seem to be wrong if enabling one domain depends on things setup by another domain ? Regards, Hans
