[PATCH v3 05/10] platform/mellanox: mlxreg-hotplug: Add support for new flavor of capability registers

[Vadim Pasternak <vadimp@nvidia.com>]

Hotplug platform data is common across the various systems, while
hotplug driver should be able to configure only the instances relevant
to specific system.

For example, platform hoptplug data might contain descriptions for fan1,
fan2, ..., fan{n}, while some systems equipped with all 'n' fans,
others with less.
Same for power units, power controllers, ASICs and so on.

For detection of the real number of equipped devices capability
registers are used.
These registers used to indicate presence of hotplug devices through
the bitmap.

For some new big modular systems, these registers will provide presence
by counters.

Use slot parameter to determine whether capability register contains
bitmask or counter.

Some 'capability' registers can be shared between different resources.
Use fields 'capability_bit' and 'capability_mask' for getting only
relevant capability bits.

Reviewed-by: Felix Radensky <fradensky@nvidia.com>
Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
---
v2->v3
Comments pointed out by Ilpo:
- Change rol32() to shift left.
---
 drivers/platform/mellanox/mlxreg-hotplug.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/mellanox/mlxreg-hotplug.c b/drivers/platform/mellanox/mlxreg-hotplug.c
index 0ce9fff1f7d4..c525b8754d48 100644
--- a/drivers/platform/mellanox/mlxreg-hotplug.c
+++ b/drivers/platform/mellanox/mlxreg-hotplug.c
@@ -274,6 +274,12 @@ static int mlxreg_hotplug_attr_init(struct mlxreg_hotplug_priv_data *priv)
 			if (ret)
 				return ret;
 
+			if (!regval)
+				continue;
+
+			/* Remove non-relevant bits. */
+			if (item->capability_mask)
+				regval = (regval & item->capability_mask) << item->capability_bit;
 			item->mask = GENMASK((regval & item->mask) - 1, 0);
 		}
 
@@ -294,7 +300,19 @@ static int mlxreg_hotplug_attr_init(struct mlxreg_hotplug_priv_data *priv)
 				if (ret)
 					return ret;
 
-				if (!(regval & data->bit)) {
+				/*
+				 * In case slot field is provided, capability
+				 * register contains counter, otherwise bitmask.
+				 * Skip non-relevant entries if slot set and
+				 * exceeds counter. Othewise validate entry by
+				 * matching bitmask.
+				 */
+				if (data->capability_mask)
+					regval = (regval & item->capability_mask) <<
+						 item->capability_bit;
+				if (data->slot > regval) {
+					break;
+				} else if (!(regval & data->bit) && !data->slot) {
 					data++;
 					continue;
 				}
@@ -611,7 +629,7 @@ static int mlxreg_hotplug_set_irq(struct mlxreg_hotplug_priv_data *priv)
 				if (ret)
 					goto out;
 
-				if (!(regval & data->bit))
+				if (!(regval & data->bit) && !data->slot)
 					item->mask &= ~BIT(j);
 			}
 		}
-- 
2.44.0