Added quirk for Surface Go touchscreen - #100
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qzed
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Do you plan on taking this upstream? |
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I can try and see if they want it. This is more of a workaround than a real solution though. I think the reason why it reports having a battery is that the device does not get identified properly so it uses the default values for most properties which just so happens to be true for having a battery. Adding it as a quirk is just kicking the can down the road until someone makes a custom driver. |
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Given that there isn't any driver like this in the works yet (AFAIK), it's probably a good idea to have that upstream. It can always be removed later on. Also there seem to be at least two other workarounds of this sort (7c38e76, decfe49), so this might be a more or less common issue. |
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Patch submitted upstream. I'll let you know how it goes. |
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Patch applied upstream! 🥳 |
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Awesome, thanks! |
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With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we get: BUG: scheduling while atomic: swapper/1/0/0x00000000 no locks held by swapper/1/0. CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ linux-surface#100 Call Trace: dump_stack_lvl+0xac/0x108 __schedule_bug+0xac/0xe0 __schedule+0xcf8/0x10d0 schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 cpu_startup_entry+0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14 This is because powerpc's arch_cpu_idle_dead() decrements the idle task's preempt count, for reasons explained in commit a7c2bb8 ("powerpc: Re-enable preemption before cpu_die()"), specifically "start_secondary() expects a preempt_count() of 0." However, since commit 2c669ef ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") and commit f1a0a37 ("sched/core: Initialize the idle task with preemption disabled"), that justification no longer holds. The idle task isn't supposed to re-enable preemption, so remove the vestigial preempt_enable() from the CPU offline path. Tested with pseries and powernv in qemu, and pseries on PowerVM. Fixes: 2c669ef ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211015173902.2278118-1-nathanl@linux.ibm.com
[ Upstream commit 787252a ] With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we get: BUG: scheduling while atomic: swapper/1/0/0x00000000 no locks held by swapper/1/0. CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100 Call Trace: dump_stack_lvl+0xac/0x108 __schedule_bug+0xac/0xe0 __schedule+0xcf8/0x10d0 schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 cpu_startup_entry+0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14 This is because powerpc's arch_cpu_idle_dead() decrements the idle task's preempt count, for reasons explained in commit a7c2bb8 ("powerpc: Re-enable preemption before cpu_die()"), specifically "start_secondary() expects a preempt_count() of 0." However, since commit 2c669ef ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") and commit f1a0a37 ("sched/core: Initialize the idle task with preemption disabled"), that justification no longer holds. The idle task isn't supposed to re-enable preemption, so remove the vestigial preempt_enable() from the CPU offline path. Tested with pseries and powernv in qemu, and pseries on PowerVM. Fixes: 2c669ef ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211015173902.2278118-1-nathanl@linux.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
The Elantech touchscreen/digitizer in the Surface Go mistakenly shows up as having capable of reporting battery (even though it actually cannot). This results in a "low battery" message popping up every time you try to use the pen. This patch adds a quirk allowing the kernel to ignore the the non-existent battery and get rid of the false low battery messages.