[PATCH 2/2] drm/i915: abstract i2c bit banging fallback in gmbus xfer

Jani Nikula
2015-12-01T14:28:26Z

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.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
drivers/gpu/drm/i915/intel_i2c.c | 39 +++++++++++++++++++++++++--------------
1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index ccb522c176bd..e26e22a72e3b 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -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 @@ timeout:
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;
--
2.1.4