[PATCH v1 2/4] platform/x86: mlx-platform: Add differed bus functionality

[Vadim Pasternak]

Add deferred bus functionality in order to enforce probing flow execution
order. Driver mlx-platform activates platform driver i2c-mux-reg, which
creates busses infrastructure, after that it activates mlxreg-hotplug
driver, which uses these busses, for connecting devices. The possible
miss-ordering can happened, for example in case the probing routine of
mlxreg-hotplug is already started execution, while i2c-mux-reg probing
routine is not completed yet. In such situation the first one could
attempt to connect device to adapter number, which is not created yet.
And as a result this connection will fail. In order to ensure the order of
probing execution on mlxreg-hotplug probe routine will be deferred until
all the busses is not created by  probe routine of i2c-mux-reg.
In order to ensure the flow order, mlx-platform driver passes the highest
bus number to the mlxreg-hotplug platform data, which in their turn could
wait in the deferred state, until all the necessary buses topology is not
exist.

Signed-off-by: Vadim Pasternak <vadimp@xxxxxxxxxxxx>
---
 drivers/platform/mellanox/mlxreg-hotplug.c |  7 +++++++
 drivers/platform/x86/mlx-platform.c        | 10 ++++++++++
 include/linux/platform_data/mlxreg.h       |  2 ++
 3 files changed, 19 insertions(+)

diff --git a/drivers/platform/mellanox/mlxreg-hotplug.c b/drivers/platform/mellanox/mlxreg-hotplug.c
index 313cf8a..fe4910b 100644
--- a/drivers/platform/mellanox/mlxreg-hotplug.c
+++ b/drivers/platform/mellanox/mlxreg-hotplug.c
@@ -550,6 +550,7 @@ static int mlxreg_hotplug_probe(struct platform_device *pdev)
 {
 	struct mlxreg_core_hotplug_platform_data *pdata;
 	struct mlxreg_hotplug_priv_data *priv;
+	struct i2c_adapter *deferred_adap;
 	int err;
 
 	pdata = dev_get_platdata(&pdev->dev);
@@ -558,6 +559,12 @@ static int mlxreg_hotplug_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	/* Defer probing if the necessary adapter is not configured yet. */
+	deferred_adap = i2c_get_adapter(pdata->deferred_nr);
+	if (!deferred_adap)
+		return -EPROBE_DEFER;
+	i2c_put_adapter(deferred_adap);
+
 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
diff --git a/drivers/platform/x86/mlx-platform.c b/drivers/platform/x86/mlx-platform.c
index 71b452a..67f3c6d 100644
--- a/drivers/platform/x86/mlx-platform.c
+++ b/drivers/platform/x86/mlx-platform.c
@@ -697,6 +697,8 @@ static int __init mlxplat_dmi_default_matched(const struct dmi_system_id *dmi)
 				ARRAY_SIZE(mlxplat_default_channels[i]);
 	}
 	mlxplat_hotplug = &mlxplat_mlxcpld_default_data;
+	mlxplat_hotplug->deferred_nr =
+		mlxplat_default_channels[i - 1][MLXPLAT_CPLD_GRP_CHNL_NUM - 1];
 
 	return 1;
 };
@@ -711,6 +713,8 @@ static int __init mlxplat_dmi_msn21xx_matched(const struct dmi_system_id *dmi)
 				ARRAY_SIZE(mlxplat_msn21xx_channels);
 	}
 	mlxplat_hotplug = &mlxplat_mlxcpld_msn21xx_data;
+	mlxplat_hotplug->deferred_nr =
+		mlxplat_msn21xx_channels[MLXPLAT_CPLD_GRP_CHNL_NUM - 1];
 
 	return 1;
 };
@@ -725,6 +729,8 @@ static int __init mlxplat_dmi_msn274x_matched(const struct dmi_system_id *dmi)
 				ARRAY_SIZE(mlxplat_msn21xx_channels);
 	}
 	mlxplat_hotplug = &mlxplat_mlxcpld_msn274x_data;
+	mlxplat_hotplug->deferred_nr =
+		mlxplat_msn21xx_channels[MLXPLAT_CPLD_GRP_CHNL_NUM - 1];
 
 	return 1;
 };
@@ -739,6 +745,8 @@ static int __init mlxplat_dmi_msn201x_matched(const struct dmi_system_id *dmi)
 				ARRAY_SIZE(mlxplat_msn21xx_channels);
 	}
 	mlxplat_hotplug = &mlxplat_mlxcpld_msn201x_data;
+	mlxplat_hotplug->deferred_nr =
+		mlxplat_default_channels[i - 1][MLXPLAT_CPLD_GRP_CHNL_NUM - 1];
 
 	return 1;
 };
@@ -753,6 +761,8 @@ static int __init mlxplat_dmi_qmb7xx_matched(const struct dmi_system_id *dmi)
 				ARRAY_SIZE(mlxplat_msn21xx_channels);
 	}
 	mlxplat_hotplug = &mlxplat_mlxcpld_default_ng_data;
+	mlxplat_hotplug->deferred_nr =
+		mlxplat_msn21xx_channels[MLXPLAT_CPLD_GRP_CHNL_NUM - 1];
 
 	return 1;
 };
diff --git a/include/linux/platform_data/mlxreg.h b/include/linux/platform_data/mlxreg.h
index fcdc707..2629109 100644
--- a/include/linux/platform_data/mlxreg.h
+++ b/include/linux/platform_data/mlxreg.h
@@ -129,6 +129,7 @@ struct mlxreg_core_platform_data {
  * @mask: top aggregation interrupt common mask;
  * @cell_low: location of low aggregation interrupt register;
  * @mask_low: low aggregation interrupt common mask;
+ * @deferred_nr: I2C adapter number must be exist prior probing execution;
  */
 struct mlxreg_core_hotplug_platform_data {
 	struct mlxreg_core_item *items;
@@ -139,6 +140,7 @@ struct mlxreg_core_hotplug_platform_data {
 	u32 mask;
 	u32 cell_low;
 	u32 mask_low;
+	int deferred_nr;
 };
 
 #endif /* __LINUX_PLATFORM_DATA_MLXREG_H */
-- 
2.1.4