[PATCH net-next v2 8/9] ice: dpll: update locking comments

[Ivan Vecera <ivecera@redhat.com>]

Callbacks run under the DPLL core domain locks instead of dpll_lock. On
E825 the TXC DPLL, the TSPLL DPLL and the other objects of a PF are in
three domains, and callbacks of pins of an external DPLL run under the
domain of that DPLL, so only pf->dplls.lock serializes them with each
other.

Reviewed-by: Petr Oros <poros@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
Changes in v2:
- Described the three domains of an E825 PF (Sashiko)
---
 drivers/net/ethernet/intel/ice/ice_dpll.c | 4 ++--
 drivers/net/ethernet/intel/ice/ice_dpll.h | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_dpll.c b/drivers/net/ethernet/intel/ice/ice_dpll.c
index 0877827a6521cc..5d0a52d86f03e8 100644
--- a/drivers/net/ethernet/intel/ice/ice_dpll.c
+++ b/drivers/net/ethernet/intel/ice/ice_dpll.c
@@ -1178,8 +1178,8 @@ ice_dpll_input_state_get(const struct dpll_pin *pin, void *pin_priv,
  * peer via dpll netlink learn about the update.
  *
  * Context: Called from dpll_pin_ops callbacks after pf->dplls.lock is
- *          released.  Uses __dpll_pin_change_ntf() because dpll_lock is
- *          still held by the dpll netlink layer.
+ *          released.  Uses __dpll_pin_change_ntf() because the domain lock
+ *          is still held by the dpll core.
  */
 static void ice_dpll_sw_pin_notify_peer(struct ice_dplls *d,
 					struct ice_dpll_pin *changed)
diff --git a/drivers/net/ethernet/intel/ice/ice_dpll.h b/drivers/net/ethernet/intel/ice/ice_dpll.h
index bce0bea9a664bc..c522c5fcbcce52 100644
--- a/drivers/net/ethernet/intel/ice/ice_dpll.h
+++ b/drivers/net/ethernet/intel/ice/ice_dpll.h
@@ -164,6 +164,11 @@ struct ice_dpll {
  *     tx_refclks usage map), acquire pf->dplls.lock first, then
  *     ctrl_pf->dplls.lock. Skip the second acquire when pf == ctrl_pf
  *     to avoid recursive locking.
+ *   - The DPLL core serializes callbacks per (module, clock_id) domain. On
+ *     E825 the TXC DPLL, the TSPLL DPLL and the other objects of a PF, such
+ *     as the RCLK pin, use three different clock_ids, and callbacks of the
+ *     SYNCE and TIME_REF pins of an external DPLL run under the domain of
+ *     that DPLL, so only @lock serializes all of them with each other.
  *   - @txclk_notify_rwsem is held for read across
  *     ice_txclk_update_and_notify(), including the out-of-lock
  *     dpll_*_change_ntf() calls. ice_dpll_deinit() takes the write side
-- 
2.56.0