From 7f58aabc369014fda3a4a33604ba0a1b63b941ac Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 30 Mar 2011 16:20:43 +0100 Subject: [PATCH] drm/i915: Reset GMBUS controller after NAK Once a NAK has been asserted by the slave, we need to reset the GMBUS controller in order to continue. This is done by asserting the Software Clear Interrupt bit and then clearing it again to restore operations. If we don't clear the NAK, then all future GMBUS xfers will fail, including DDC probes and EDID retrieval. v2: Add some comments as suggested by Keith Packard. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35781 Signed-off-by: Chris Wilson Reviewed-by: Keith Packard Tested-by: Jesse Barnes Tested-by: "Mengmeng Meng" --- drivers/gpu/drm/i915/intel_i2c.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 82d04c5..d3b903b 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -259,7 +259,7 @@ gmbus_xfer(struct i2c_adapter *adapter, if (wait_for(I915_READ(GMBUS2 + reg_offset) & (GMBUS_SATOER | GMBUS_HW_RDY), 50)) goto timeout; if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) - return 0; + goto clear_err; val = I915_READ(GMBUS3 + reg_offset); do { @@ -287,7 +287,7 @@ gmbus_xfer(struct i2c_adapter *adapter, if (wait_for(I915_READ(GMBUS2 + reg_offset) & (GMBUS_SATOER | GMBUS_HW_RDY), 50)) goto timeout; if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) - return 0; + goto clear_err; val = loop = 0; do { @@ -302,14 +302,31 @@ gmbus_xfer(struct i2c_adapter *adapter, if (i + 1 < num && wait_for(I915_READ(GMBUS2 + reg_offset) & (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE), 50)) goto timeout; if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) - return 0; + goto clear_err; } - return num; + goto done; + +clear_err: + /* Toggle the Software Clear Interrupt bit. This has the effect + * of resetting the GMBUS controller and so clearing the + * BUS_ERROR raised by the slave's NAK. + */ + I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT); + I915_WRITE(GMBUS1 + reg_offset, 0); + +done: + /* Mark the GMBUS interface as disabled. We will re-enable it at the + * start of the next xfer, till then let it sleep. + */ + I915_WRITE(GMBUS0 + reg_offset, 0); + return i; timeout: DRM_INFO("GMBUS timed out, falling back to bit banging on pin %d [%s]\n", bus->reg0 & 0xff, bus->adapter.name); + I915_WRITE(GMBUS0 + reg_offset, 0); + /* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */ bus->force_bit = intel_gpio_create(dev_priv, bus->reg0 & 0xff); if (!bus->force_bit) -- 2.7.4