[PATCH 8/8 v7] drm/i915/intel_i2c: use DRM_ERROR on timeouts

Daniel Kurtz
2012-03-30T11:47:37Z

GMBUS should hopefully actually work now in most cases.
So, report any timeout conditions using DRM_ERROR(), especially for the
case where the timeout causes fallback to bit-bang mode.

>From observations, the GMBUS transfers timeout and switch to Bit-Banging
when the corresponding pins are not actually hooked up to anything. In
these cases, there is no NAK, nor timeout, nor any other indication from
the GMBUS controller that a transaction fails. The first gmbus
transaction timeout is caught by the "wait_for" timeout, causing the
transition to bit-banging mode for subsequent (failed) attempts.

This might be what was meant by the following note in the GPIO_CTL
description:
"The registers that control digital display (HDMI/DVI, DisplayPort)
pins should only be utilized if the Port Detected bit in the related
control register is set to 1."
(http://intellinuxgraphics.org/documentation/SNB/IHD_OS_Vol3_Part3.pdf,
section 2.2.2)

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
---
drivers/gpu/drm/i915/intel_i2c.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 73431ed..154fedd 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -380,8 +380,8 @@ gmbus_xfer(struct i2c_adapter *adapter,
*/
if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
10)) {
- DRM_INFO("GMBUS [%s] timed out waiting for idle\n",
- adapter->name);
+ DRM_ERROR("GMBUS [%s] timed out waiting for idle\n",
+ adapter->name);
ret = -ETIMEDOUT;
}
I915_WRITE(GMBUS0 + reg_offset, 0);
@@ -396,7 +396,7 @@ clear_err:
*/
if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
10))
- DRM_INFO("GMBUS [%s] timed out after NAK\n", adapter->name);
+ DRM_ERROR("GMBUS [%s] timed out after NAK\n", adapter->name);

/* Toggle the Software Clear Interrupt bit. This has the effect
* of resetting the GMBUS controller and so clearing the
@@ -421,8 +421,8 @@ clear_err:
goto out;

timeout:
- DRM_INFO("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
- bus->adapter.name, bus->reg0 & 0xff);
+ DRM_ERROR("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
+ bus->adapter.name, bus->reg0 & 0xff);
I915_WRITE(GMBUS0 + reg_offset, 0);

/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
--
1.7.7.3