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drm/i915: abstract i2c bit banging fallback in gmbus xfer
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Choose between i2c bit banging and gmbus in a new higher level function,
and let the i2c core retry the first time we fall back to bit banging.

The i2c core imposes a timeout on -EAGAIN, but it defaults to 1 second,
and shouldn't be a problem for us.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448980166-23055-2-git-send-email-jani.nikula@intel.com
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Jani Nikula committed Dec 2, 2015
1 parent 0aeb904 commit bffce90
Showing 1 changed file with 25 additions and 14 deletions.
39 changes: 25 additions & 14 deletions drivers/gpu/drm/i915/intel_i2c.c
Original file line number Diff line number Diff line change
@@ -472,9 +472,7 @@ gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)
}

static int
gmbus_xfer(struct i2c_adapter *adapter,
struct i2c_msg *msgs,
int num)
do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
{
struct intel_gmbus *bus = container_of(adapter,
struct intel_gmbus,
@@ -483,14 +481,6 @@ gmbus_xfer(struct i2c_adapter *adapter,
int i = 0, inc, try = 0;
int ret = 0;

intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
mutex_lock(&dev_priv->gmbus_mutex);

if (bus->force_bit) {
ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
goto out;
}

retry:
I915_WRITE(GMBUS0, bus->reg0);

@@ -585,13 +575,34 @@ gmbus_xfer(struct i2c_adapter *adapter,
bus->adapter.name, bus->reg0 & 0xff);
I915_WRITE(GMBUS0, 0);

/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
/*
* Hardware may not support GMBUS over these pins? Try GPIO bitbanging
* instead. Use EAGAIN to have i2c core retry.
*/
bus->force_bit = 1;
ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
ret = -EAGAIN;

out:
mutex_unlock(&dev_priv->gmbus_mutex);
return ret;
}

static int
gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
{
struct intel_gmbus *bus = container_of(adapter, struct intel_gmbus,
adapter);
struct drm_i915_private *dev_priv = bus->dev_priv;
int ret;

intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
mutex_lock(&dev_priv->gmbus_mutex);

if (bus->force_bit)
ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
else
ret = do_gmbus_xfer(adapter, msgs, num);

mutex_unlock(&dev_priv->gmbus_mutex);
intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);

return ret;

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