[Intel-gfx] [PATCH 22/49] drm/i915/bxt: Avoid registering unused gmbus ports as i2c adapter

[Imre Deak]

From: "A.Sunil Kamath" <sunil.kamath at intel.com>

Though we populate all gmbus ports during setup_gmbus, only
valid ones should be registered to i2c adapters. This is
important as userspace can directly interact with the i2c bus.

While populating gmbus register we ensure that unused ports
will have gpio_reg value set as 0. This patch ensures that
only those with non zero gpio reg will get registered as i2c
adapter and this is applicable for all platforms.

del_adapter will check if the adaptor was really added
before, still its better to avoid unnecessary calls to the same.
This patch also adds a check to deregister only added i2c adapters.

Tested using i2c-tools to confirm that only valid gmbus ports
are registered as i2c adapter.

BXT will have only valid i2c adapters as below:
i2c-x      i2c     i915 gmbus dpc      I2C adapter
i2c-x+1    i2c     i915 gmbus dpb      I2C adapter
i2c-x+2    i2c     i915 gmbus misc     I2C adapter

v1: This patch is added as per review comments from
Daniel Vetter on gmbus BXT patch

Issue: VIZ-3574
Signed-off-by: A.Sunil Kamath <sunil.kamath at intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
---
 drivers/gpu/drm/i915/intel_i2c.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 06892b5..d5ca310 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -599,9 +599,12 @@ int intel_setup_gmbus(struct drm_device *dev)
 
 		intel_gpio_setup(bus, port);
 
-		ret = i2c_add_adapter(&bus->adapter);
-		if (ret)
-			goto err;
+		/* Do not register unused gmbus ports as i2c adapter */
+		if (bus->gpio_reg) {
+			ret = i2c_add_adapter(&bus->adapter);
+			if (ret)
+				goto err;
+		}
 	}
 
 	intel_i2c_reset(dev_priv->dev);
@@ -611,7 +614,8 @@ int intel_setup_gmbus(struct drm_device *dev)
 err:
 	while (--i) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];
-		i2c_del_adapter(&bus->adapter);
+		if (bus->gpio_reg)
+			i2c_del_adapter(&bus->adapter);
 	}
 	return ret;
 }
@@ -652,6 +656,7 @@ void intel_teardown_gmbus(struct drm_device *dev)
 
 	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];
-		i2c_del_adapter(&bus->adapter);
+		if (bus->gpio_reg)
+			i2c_del_adapter(&bus->adapter);
 	}
 }
-- 
2.1.0