platform/x86: mlx-platform: Add deffered bus functionality

mlx-platform activates i2c-mux-reg, which creates buses needed by
mlxreg-hotplug. If the mlxreg-hotplug probe runs before the i2c-mux-reg
probe completes, it may attempt to connect a device to an adapter number
that has not been created yet, and fail.

Make mlx-platform driver record the highest bus number in mlxreg-hotplug
platform data and defer mlxreg-hotplug probe until all the buses are
created.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
[dvhart: rewrite commit message more concisely]
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

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;

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;
 };

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 */