Some GMBUS devices fail to report NAKs (even recent Skylakes), resulting in us hitting the 50ms timeout every time we try to read an EDID on a disconnected device. Try a quick GPIO discovery first by setting the clock line and seeing if the device responds.
Signed-off-by: Chris Wilson <[email protected]> Cc: David Weinehall <[email protected]> --- drivers/gpu/drm/i915/intel_i2c.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 6841c41281a3..72945a7c5547 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -461,6 +461,22 @@ gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs) return ret; } +static bool gpio_is_alive(struct intel_gmbus *bus) +{ + bool result = true; + + intel_i2c_quirk_set(bus->dev_priv, true); + set_clock(bus, 1); + + if (wait_for_us(get_clock(bus), 10) && wait_for(get_clock(bus), 2)) + result = false; + + set_clock(bus, 0); + intel_i2c_quirk_set(bus->dev_priv, false); + + return result; +} + static int do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num) { @@ -474,6 +490,13 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num) int i = 0, inc, try = 0; int ret = 0; + /* Some GMBUS devices fail to report NAKs and so we hit the 50ms + * timeout, every time. Try a quick GPIO discovery first by seeing + * if the device responds to setting the clock line high. + */ + if (!gpio_is_alive(bus)) + return -ENXIO; + intel_uncore_forcewake_get(dev_priv, fw); retry: I915_WRITE_FW(GMBUS0, bus->reg0); -- 2.9.3 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
