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authorH. Nikolaus Schaller <hns@goldelico.com>2020-05-23 19:32:56 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-06-22 09:33:11 +0200
commit4033c367eebea259241c9a6ba37ea9e9aeb75d83 (patch)
tree12a2cfd12a6c6ef8cf4141f7eb4537caffacb478 /fs/jfs/inode.c
parentd7603a157a0953f43a6d41d57a7f1be829b212f0 (diff)
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w1: omap-hdq: fix interrupt handling which did show spurious timeouts
commit 13db4c40fe0b20b80c7d1c91a9da8411e26b5c27 upstream. Since commit 27d13da8782a ("w1: omap-hdq: Simplify driver with PM runtime autosuspend") was applied, I did see timeouts and wrong values when reading a bq27000 connected to hdq of the omap3. This occurred mainly after boot but remained and only sometimes settled down after several reads. root@letux:~# time cat /sys/class/power_supply/bq27000-battery/uevent POWER_SUPPLY_NAME=bq27000-battery POWER_SUPPLY_STATUS=Discharging POWER_SUPPLY_PRESENT=1 POWER_SUPPLY_VOLTAGE_NOW=0 POWER_SUPPLY_CURRENT_NOW=0 POWER_SUPPLY_CAPACITY=0 POWER_SUPPLY_CAPACITY_LEVEL=Normal POWER_SUPPLY_TEMP=-2731 POWER_SUPPLY_TIME_TO_EMPTY_NOW=0 POWER_SUPPLY_TIME_TO_EMPTY_AVG=0 POWER_SUPPLY_TIME_TO_FULL_NOW=0 POWER_SUPPLY_TECHNOLOGY=Li-ion POWER_SUPPLY_CHARGE_FULL=0 POWER_SUPPLY_CHARGE_NOW=0 POWER_SUPPLY_CHARGE_FULL_DESIGN=0 POWER_SUPPLY_CYCLE_COUNT=0 POWER_SUPPLY_ENERGY_NOW=0 POWER_SUPPLY_POWER_AVG=0 POWER_SUPPLY_HEALTH=Good POWER_SUPPLY_MANUFACTURER=Texas Instruments real    0m15.761s user    0m0.001s sys     0m0.025s root@letux:~# Sometimes the effect did disappear after accessing the device multiple times, speed went up and results became correct. All this indicates that some interrupts from the hdq controller are lost by the driver. Enabling debugging revealed that there were spurious tx and rx timeouts, i.e. the driver does not always recognise interrupts. The main problem is that rx and tx interrupts share a single variable which was sometimes reset to 0 wiping out other interrupts. And it was overwritten by a second interrupt, independent of whether the previous interrupt was already processed or not. This patch improves interrupt handling to avoid such races and loss of interrupt flags. The ideas are: * only the hdq_isr() sets bits in hdq_status * it does not reset any bits * it does wake_up() if any interrupt is pending * bits are only reset by the read/write/break functions if they were waited for * this makes sure that no interrupts can be lost * rx/tx/timeout bits are completely decoupled from each other (and not reset all after waiting for any of them) * which bits to reset is now specified by a new parameter to hdq_reset_irqstatus() * hdq_reset_irqstatus() also returns the state before resetting so that we can encapsulate the spinlock * this should now handle the case that the write and read are both already finished quickly before the hdq_write_byte() ends. * Or that two interrupts occur in succession before they are processed by the driver. Old code may have reset all status bits making the next hdq_read_byte() timeout. * the spinlock now always protects changing of bits in function hdq_reset_irqstatus() which could become a read-write-modify problem if the interrupt handler tries to read-modify-write exactly at the same moment * we add mutex protection also for hdq_write_byte() just to be safe to not to disturb a hdq_read_byte() triggered by some other thread/process. This patch was tested on a GTA04 and results in no boot problems any more. And first read after boot is now ok: root@letux:~# time cat /sys/class/power_supply/bq27000-battery/uevent POWER_SUPPLY_NAME=bq27000-battery POWER_SUPPLY_STATUS=Discharging POWER_SUPPLY_PRESENT=1 POWER_SUPPLY_VOLTAGE_NOW=3970000 POWER_SUPPLY_CURRENT_NOW=354144 POWER_SUPPLY_CAPACITY=82 POWER_SUPPLY_CAPACITY_LEVEL=Normal POWER_SUPPLY_TEMP=266 POWER_SUPPLY_TIME_TO_EMPTY_NOW=7680 POWER_SUPPLY_TIME_TO_EMPTY_AVG=7380 POWER_SUPPLY_TECHNOLOGY=Li-ion POWER_SUPPLY_CHARGE_FULL=934856 POWER_SUPPLY_CHARGE_NOW=763976 POWER_SUPPLY_CHARGE_FULL_DESIGN=1233792 POWER_SUPPLY_CYCLE_COUNT=82 POWER_SUPPLY_ENERGY_NOW=2852840 POWER_SUPPLY_POWER_AVG=1392840 POWER_SUPPLY_HEALTH=Good POWER_SUPPLY_MANUFACTURER=Texas Instruments real 0m0.233s user 0m0.000s sys 0m0.025s root@letux:~# It was also tested with dev_dbg enabled and more printk that all activities behave correctly, especially hdq_write_byte(), hdq_read_byte(), omap_hdq_break(). Not tested is omap_w1_triplet(). Fixes: 27d13da8782a ("w1: omap-hdq: Simplify driver with PM runtime autosuspend") Cc: stable@vger.kernel.org # v5.6+ Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com> Link: https://lore.kernel.org/r/68fc8623ae741878beef049273696d2377526165.1590255176.git.hns@goldelico.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/jfs/inode.c')
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