drm/i915: Add CHV PHY LDO power sanity checks
At various points when changing the DPIO lane/phy power states, construct an expected value of the DISPLAY_PHY_STATUS register and compare it with the real thing. To construct the expected value we look at our shadow PHY_CONTROL register value (which should match what we've just written to the hardware), and we also need to look at the actual state of the cmn power wells as a disabled power well causes the relevant LDO status to be reported as 'on' in DISPLAY_PHY_STATUS. When initially powering up the PHY it performs various internal calibrations for which it fully powers up. That means that if we check for the expetected power state immediately upon releasing cmnreset we would get the occasional false positive. But we can of course poll until the expected value appears. It shouldn't be too long so this shouldn't make modesets substantially longer. One extra complication is introduced when we cross the streams, ie. drive port B with pipe B. In this case we trick CL2 (where the DPLL lives) into life by temporaily powering up the lanes in the second channel, and once the pipe is up and runnign we release the lane power override. At that point the power state of CL2 has somehow gotten entangled with the power state of the first channel. That means that constructing the expected DISPLAY_PHY_STATUS value is a bit tricky since based on the lane power states in the second channel, CL2 should also be powered down. But we can use the DPLL enable bit to determine when CL2 should be alive even if the lanes are powered down. However the power state of CL2 isn't actually tied in with the DPLL state, but to the state of the lanes in first channel, so we have to avoid checking the expected state between shutting down the DPLL and powering down the lanes in the first channel. So no calling assert_chv_phy_status() before the DISPLAY_PHY_CONTROL write in chv_phy_powergate_lanes(), but after the write is a safe time to check. Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: NDeepak S <deepak.s@linux.intel.com> Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Showing
想要评论请 注册 或 登录