From 0e2bddf9e5f926ce32ed635012d0f8a0b54075d5 Mon Sep 17 00:00:00 2001 From: Michal Schmidt Date: Tue, 26 Mar 2024 00:20:37 +0100 Subject: ice: add ice_adapter for shared data across PFs on the same NIC There is a need for synchronization between ice PFs on the same physical adapter. Add a "struct ice_adapter" for holding data shared between PFs of the same multifunction PCI device. The struct is refcounted - each ice_pf holds a reference to it. Its first use will be for PTP. I expect it will be useful also to improve the ugliness that is ice_prot_id_tbl. Reviewed-by: Przemek Kitszel Signed-off-by: Michal Schmidt Tested-by: Pucha Himasekhar Reddy (A Contingent worker at Intel) Signed-off-by: Tony Nguyen --- drivers/net/ethernet/intel/ice/ice_adapter.c | 114 +++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) create mode 100644 drivers/net/ethernet/intel/ice/ice_adapter.c (limited to 'drivers/net/ethernet/intel/ice/ice_adapter.c') diff --git a/drivers/net/ethernet/intel/ice/ice_adapter.c b/drivers/net/ethernet/intel/ice/ice_adapter.c new file mode 100644 index 000000000000..f00ab998e853 --- /dev/null +++ b/drivers/net/ethernet/intel/ice/ice_adapter.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0-only +// SPDX-FileCopyrightText: Copyright Red Hat + +#include +#include +#include +#include +#include +#include +#include "ice_adapter.h" + +static DEFINE_XARRAY(ice_adapters); + +/* PCI bus number is 8 bits. Slot is 5 bits. Domain can have the rest. */ +#define INDEX_FIELD_DOMAIN GENMASK(BITS_PER_LONG - 1, 13) +#define INDEX_FIELD_BUS GENMASK(12, 5) +#define INDEX_FIELD_SLOT GENMASK(4, 0) + +static unsigned long ice_adapter_index(const struct pci_dev *pdev) +{ + unsigned int domain = pci_domain_nr(pdev->bus); + + WARN_ON(domain > FIELD_MAX(INDEX_FIELD_DOMAIN)); + + return FIELD_PREP(INDEX_FIELD_DOMAIN, domain) | + FIELD_PREP(INDEX_FIELD_BUS, pdev->bus->number) | + FIELD_PREP(INDEX_FIELD_SLOT, PCI_SLOT(pdev->devfn)); +} + +static struct ice_adapter *ice_adapter_new(void) +{ + struct ice_adapter *adapter; + + adapter = kzalloc(sizeof(*adapter), GFP_KERNEL); + if (!adapter) + return NULL; + + refcount_set(&adapter->refcount, 1); + + return adapter; +} + +static void ice_adapter_free(struct ice_adapter *adapter) +{ + kfree(adapter); +} + +DEFINE_FREE(ice_adapter_free, struct ice_adapter*, if (_T) ice_adapter_free(_T)) + +/** + * ice_adapter_get - Get a shared ice_adapter structure. + * @pdev: Pointer to the pci_dev whose driver is getting the ice_adapter. + * + * Gets a pointer to a shared ice_adapter structure. Physical functions (PFs) + * of the same multi-function PCI device share one ice_adapter structure. + * The ice_adapter is reference-counted. The PF driver must use ice_adapter_put + * to release its reference. + * + * Context: Process, may sleep. + * Return: Pointer to ice_adapter on success. + * ERR_PTR() on error. -ENOMEM is the only possible error. + */ +struct ice_adapter *ice_adapter_get(const struct pci_dev *pdev) +{ + struct ice_adapter *ret, __free(ice_adapter_free) *adapter = NULL; + unsigned long index = ice_adapter_index(pdev); + + adapter = ice_adapter_new(); + if (!adapter) + return ERR_PTR(-ENOMEM); + + xa_lock(&ice_adapters); + ret = __xa_cmpxchg(&ice_adapters, index, NULL, adapter, GFP_KERNEL); + if (xa_is_err(ret)) { + ret = ERR_PTR(xa_err(ret)); + goto unlock; + } + if (ret) { + refcount_inc(&ret->refcount); + goto unlock; + } + ret = no_free_ptr(adapter); +unlock: + xa_unlock(&ice_adapters); + return ret; +} + +/** + * ice_adapter_put - Release a reference to the shared ice_adapter structure. + * @pdev: Pointer to the pci_dev whose driver is releasing the ice_adapter. + * + * Releases the reference to ice_adapter previously obtained with + * ice_adapter_get. + * + * Context: Any. + */ +void ice_adapter_put(const struct pci_dev *pdev) +{ + unsigned long index = ice_adapter_index(pdev); + struct ice_adapter *adapter; + + xa_lock(&ice_adapters); + adapter = xa_load(&ice_adapters, index); + if (WARN_ON(!adapter)) + goto unlock; + + if (!refcount_dec_and_test(&adapter->refcount)) + goto unlock; + + WARN_ON(__xa_erase(&ice_adapters, index) != adapter); + ice_adapter_free(adapter); +unlock: + xa_unlock(&ice_adapters); +} -- cgit v1.2.3-59-g8ed1b From d29a8134c78232213fb88f20d7ae865ec364e367 Mon Sep 17 00:00:00 2001 From: Michal Schmidt Date: Tue, 26 Mar 2024 00:20:38 +0100 Subject: ice: avoid the PTP hardware semaphore in gettimex64 path The PTP hardware semaphore (PFTSYN_SEM) is used to synchronize operations that program the PTP timers. The operations involve issuing commands to the sideband queue. The E810 does not have a hardware sideband queue, so the admin queue is used. The admin queue is slow. I have observed delays in hundreds of milliseconds waiting for ice_sq_done. When phc2sys reads the time from the ice PTP clock and PFTSYN_SEM is held by a task performing one of the slow operations, ice_ptp_lock can easily time out. phc2sys gets -EBUSY and the kernel prints: ice 0000:XX:YY.0: PTP failed to get time These messages appear once every few seconds, causing log spam. The E810 datasheet recommends an algorithm for reading the upper 64 bits of the GLTSYN_TIME register. It matches what's implemented in ice_ptp_read_src_clk_reg. It is robust against wrap-around, but not necessarily against the concurrent setting of the register (with GLTSYN_CMD_{INIT,ADJ}_TIME commands). Perhaps that's why ice_ptp_gettimex64 also takes PFTSYN_SEM. The race with time setters can be prevented without relying on the PTP hardware semaphore. Using the "ice_adapter" from the previous patch, we can have a common spinlock for the PFs that share the clock hardware. It will protect the reading and writing to the GLTSYN_TIME register. The writing is performed indirectly, by the hardware, as a result of the driver writing GLTSYN_CMD_SYNC in ice_ptp_exec_tmr_cmd. I wasn't sure if the ice_flush there is enough to make sure GLTSYN_TIME has been updated, but it works well in my testing. My test code can be seen here: https://gitlab.com/mschmidt2/linux/-/commits/ice-ptp-host-side-lock-10 It consists of: - kernel threads reading the time in a busy loop and looking at the deltas between consecutive values, reporting new maxima. - a shell script that sets the time repeatedly; - a bpftrace probe to produce a histogram of the measured deltas. Without the spinlock ptp_gltsyn_time_lock, it is easy to see tearing. Deltas in the [2G, 4G) range appear in the histograms. With the spinlock added, there is no tearing and the biggest delta I saw was in the range [1M, 2M), that is under 2 ms. Reviewed-by: Jacob Keller Reviewed-by: Przemek Kitszel Signed-off-by: Michal Schmidt Tested-by: Pucha Himasekhar Reddy (A Contingent worker at Intel) Signed-off-by: Tony Nguyen --- drivers/net/ethernet/intel/ice/ice_adapter.c | 2 ++ drivers/net/ethernet/intel/ice/ice_adapter.h | 6 ++++++ drivers/net/ethernet/intel/ice/ice_ptp.c | 8 +------- drivers/net/ethernet/intel/ice/ice_ptp_hw.c | 3 +++ 4 files changed, 12 insertions(+), 7 deletions(-) (limited to 'drivers/net/ethernet/intel/ice/ice_adapter.c') diff --git a/drivers/net/ethernet/intel/ice/ice_adapter.c b/drivers/net/ethernet/intel/ice/ice_adapter.c index f00ab998e853..52d15ef7f4b1 100644 --- a/drivers/net/ethernet/intel/ice/ice_adapter.c +++ b/drivers/net/ethernet/intel/ice/ice_adapter.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include "ice_adapter.h" @@ -35,6 +36,7 @@ static struct ice_adapter *ice_adapter_new(void) if (!adapter) return NULL; + spin_lock_init(&adapter->ptp_gltsyn_time_lock); refcount_set(&adapter->refcount, 1); return adapter; diff --git a/drivers/net/ethernet/intel/ice/ice_adapter.h b/drivers/net/ethernet/intel/ice/ice_adapter.h index cb5a02eb24c1..9d11014ec02f 100644 --- a/drivers/net/ethernet/intel/ice/ice_adapter.h +++ b/drivers/net/ethernet/intel/ice/ice_adapter.h @@ -4,15 +4,21 @@ #ifndef _ICE_ADAPTER_H_ #define _ICE_ADAPTER_H_ +#include #include struct pci_dev; /** * struct ice_adapter - PCI adapter resources shared across PFs + * @ptp_gltsyn_time_lock: Spinlock protecting access to the GLTSYN_TIME + * register of the PTP clock. * @refcount: Reference count. struct ice_pf objects hold the references. */ struct ice_adapter { + /* For access to the GLTSYN_TIME register */ + spinlock_t ptp_gltsyn_time_lock; + refcount_t refcount; }; diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c index c11eba07283c..0875f37add78 100644 --- a/drivers/net/ethernet/intel/ice/ice_ptp.c +++ b/drivers/net/ethernet/intel/ice/ice_ptp.c @@ -374,6 +374,7 @@ ice_ptp_read_src_clk_reg(struct ice_pf *pf, struct ptp_system_timestamp *sts) u8 tmr_idx; tmr_idx = ice_get_ptp_src_clock_index(hw); + guard(spinlock)(&pf->adapter->ptp_gltsyn_time_lock); /* Read the system timestamp pre PHC read */ ptp_read_system_prets(sts); @@ -1925,15 +1926,8 @@ ice_ptp_gettimex64(struct ptp_clock_info *info, struct timespec64 *ts, struct ptp_system_timestamp *sts) { struct ice_pf *pf = ptp_info_to_pf(info); - struct ice_hw *hw = &pf->hw; - - if (!ice_ptp_lock(hw)) { - dev_err(ice_pf_to_dev(pf), "PTP failed to get time\n"); - return -EBUSY; - } ice_ptp_read_time(pf, ts, sts); - ice_ptp_unlock(hw); return 0; } diff --git a/drivers/net/ethernet/intel/ice/ice_ptp_hw.c b/drivers/net/ethernet/intel/ice/ice_ptp_hw.c index 187ce9b54e1a..2b9423a173bb 100644 --- a/drivers/net/ethernet/intel/ice/ice_ptp_hw.c +++ b/drivers/net/ethernet/intel/ice/ice_ptp_hw.c @@ -274,6 +274,9 @@ void ice_ptp_src_cmd(struct ice_hw *hw, enum ice_ptp_tmr_cmd cmd) */ static void ice_ptp_exec_tmr_cmd(struct ice_hw *hw) { + struct ice_pf *pf = container_of(hw, struct ice_pf, hw); + + guard(spinlock)(&pf->adapter->ptp_gltsyn_time_lock); wr32(hw, GLTSYN_CMD_SYNC, SYNC_EXEC_CMD); ice_flush(hw); } -- cgit v1.2.3-59-g8ed1b