Commit f236464f1d ("wifi: wilc1000: convert list management to RCU")
attempted to convert SRCU to RCU usage, assuming it was not really needed.
The runtime issues that arose after merging it showed that there are code
paths involving sleeping functions, and removing those would need some
heavier driver rework.
Add some documentation about SRCU need to make sure that any future
developer do not miss some use cases if tempted to convert back again to
RCU.
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240528-wilc_revert_srcu_to_rcu-v1-3-bce096e0798c@bootlin.com
This reverts commit f236464f1d
Commit f236464f1d ("wifi: wilc1000: convert list management to RCU")
replaced SRCU with RCU, aiming to simplify RCU usage in the driver. No
documentation or commit history hinted about why SRCU has been preferred
in original design, so it has been assumed to be safe to do this
conversion.
Unfortunately, some static analyzers raised warnings, confirmed by runtime
checker, not long after the merge. At least three different issues arose
when switching to RCU:
- wilc_wlan_txq_filter_dup_tcp_ack is executed in a RCU read critical
section yet calls wait_for_completion_timeout
- wilc_wfi_init_mon_interface calls kmalloc and register_netdevice while
manipulating a vif retrieved from vif list
- set_channel sends command to chip (and so, also waits for a completion)
while holding a vif retrieved from vif list (so, in RCU read critical
section)
Some of those issues are not trivial to fix and would need bigger driver
rework. Fix those issues by reverting the SRCU to RCU conversion commit
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-wireless/3b46ec7c-baee-49fd-b760-3bc12fb12eaf@moroto.mountain/
Fixes: f236464f1d ("wifi: wilc1000: convert list management to RCU")
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240528-wilc_revert_srcu_to_rcu-v1-1-bce096e0798c@bootlin.com
Enabling CONFIG_PROVE_RCU_LIST raises many warnings in wilc driver, even on
some places already protected by a read critical section. An example of
such case is in wilc_get_available_idx:
=============================
WARNING: suspicious RCU usage
6.8.0-rc1+ #32 Not tainted
-----------------------------
drivers/net/wireless/microchip/wilc1000/netdev.c:944 RCU-list traversed in non-reader section!!
[...]
stack backtrace:
CPU: 0 PID: 26 Comm: kworker/0:3 Not tainted 6.8.0-rc1+ #32
Hardware name: Atmel SAMA5
Workqueue: events_freezable mmc_rescan
unwind_backtrace from show_stack+0x18/0x1c
show_stack from dump_stack_lvl+0x34/0x58
dump_stack_lvl from wilc_netdev_ifc_init+0x788/0x8ec
wilc_netdev_ifc_init from wilc_cfg80211_init+0x690/0x910
wilc_cfg80211_init from wilc_sdio_probe+0x168/0x490
wilc_sdio_probe from sdio_bus_probe+0x230/0x3f4
sdio_bus_probe from really_probe+0x270/0xdf4
really_probe from __driver_probe_device+0x1dc/0x580
__driver_probe_device from driver_probe_device+0x60/0x140
driver_probe_device from __device_attach_driver+0x268/0x364
__device_attach_driver from bus_for_each_drv+0x15c/0x1cc
bus_for_each_drv from __device_attach+0x1ec/0x3e8
__device_attach from bus_probe_device+0x190/0x1c0
bus_probe_device from device_add+0x10dc/0x18e4
device_add from sdio_add_func+0x1c0/0x2c0
sdio_add_func from mmc_attach_sdio+0xa08/0xe1c
mmc_attach_sdio from mmc_rescan+0xa00/0xfe0
mmc_rescan from process_one_work+0x8d4/0x169c
process_one_work from worker_thread+0x8cc/0x1340
worker_thread from kthread+0x448/0x510
kthread from ret_from_fork+0x14/0x28
This warning is due to the section being protected by a srcu critical read
section, but the list traversal being done with classic RCU API. Fix the
warning by using corresponding SRCU read lock/unlock APIs. While doing so,
since we always manipulate the same list (managed through a pointer
embedded in struct_wilc), add a macro to reduce the corresponding
boilerplate in each call site.
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240215-wilc_fix_rcu_usage-v1-2-f610e46c6f82@bootlin.com
The wakeup and sleep commands need to be sent to the WILC chip only
when it is in power save mode (PSM, as controlled by "iw dev wlan0 set
power_save on/off"). The commands are relatively costly, so it pays
to skip them when possible.
iperf3 without this patch (no significant different with PSM on/off):
TX 0.00-120.01 sec 140 MBytes 9.82 Mbits/sec
RX 0.00-120.69 sec 283 MBytes 19.6 Mbits/sec
with this patch applied:
PSM off (TX is 46% improved, RX slightly improved; may not be significant):
TX 0.00-120.00 sec 206 MBytes 14.4 Mbits/sec
RX 0.00-120.48 sec 322 MBytes 22.4 Mbits/sec
PSM on (no significant change):
TX 0.00-120.00 sec 140 MBytes 9.78 Mbits/sec
RX 0.00-120.08 sec 257 MBytes 18.0 Mbits/sec
Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211210203016.3680425-2-davidm@egauge.net
Use the correct sequence to configure clockless registers for chip wake-up.
The following sequence is expected from WILC chip for wakeup:
- set wakeup bit in wakeup_reg register
- after setting the wakeup bit, read back the clock status bit for wakeup
complete.
For SDIO/SPI modules, the wakeup sequence is the same except uses different
register values so refactored the code to use common function for both
SDIO/SPI bus.
Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210916164902.74629-5-ajay.kathat@microchip.com
Added multiple queues[BK,BE,VI,VO] to handle different priority data
packets. Before adding a packet to the queue, checked its priority from
the header, and then add to the suitable queue. The limit for each queue
is maintained separately. Also while passing the packets to the firmware
via VMM take care to select data packets based on priority and available
space.
Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201125114059.10006-6-ajay.kathat@microchip.com
