It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm
Cc: stable@vger.kernel.org
Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
---
drivers/tty/serial/8250/8250_omap.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm
Cc: stable@vger.kernel.org
How far back does this need to go? What commit id does this fix? What
caused this to just show up now vs. previously?
thanks,
greg k-h
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On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
quoted
It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm
Cc: stable@vger.kernel.org
How far back does this need to go? What commit id does this fix? What
caused this to just show up now vs. previously?
I just noticed this causes the following regression in Linux next when
pressing a key on uart console after boot at least on omap3. This seems
to happen on serial_port_in(port, UART_RX) in the quirk handling.
Vignesh, it seems this quirk needs some soc specific flag added to
it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
all the SoCs?
I think it's best to drop this patch until the issues are resolved,
also there are some open comments above that might be answered by
limiting this quirk to a specific range of SoCs :)
Regards,
Tony
8< ------------------------
#regzb introduced: 31fae7c8b18c ("serial: 8250: 8250_omap: Fix possible interrupt storm")
Internal error: : 1028 [#1] SMP ARM
Modules linked in:
CPU: 0 PID: 870 Comm: syslog Not tainted 5.13.0-rc3-next-20210527-00001-g9b545469a50f #34
Hardware name: Generic OMAP36xx (Flattened Device Tree)
PC is at mem_serial_in+0xc/0x20
LR is at omap8250_irq+0x258/0x2d4
pc : [<c06762f0>] lr : [<c0681720>] psr: 60000193
sp : c2975c90 ip : 00000000 fp : c1836000
r10: c0ff7f20 r9 : c0ff7f40 r8 : 00000058
r7 : c2975ce0 r6 : 00000000 r5 : 00000001 r4 : c1031a24
r3 : fa06a000 r2 : 00000002 r1 : 00000000 r0 : c1031a24
Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none
Control: 10c5387d Table: 829cc019 DAC: 00000051
Register r0 information: non-slab/vmalloc memory
Register r1 information: NULL pointer
Register r2 information: non-paged memory
Register r3 information: 0-page vmalloc region starting at 0xfa000000 allocated at iotable_init+0x0/0xf4
Register r4 information: non-slab/vmalloc memory
Register r5 information: non-paged memory
Register r6 information: NULL pointer
Register r7 information: non-slab/vmalloc memory
Register r8 information: non-paged memory
Register r9 information: non-slab/vmalloc memory
Register r10 information: non-slab/vmalloc memory
Register r11 information: slab kmalloc-256 start c1836000 pointer offset 0 size 256
Register r12 information: NULL pointer
Process syslog (pid: 870, stack limit = 0x64988e4e)
...
[<c06762f0>] (mem_serial_in) from [<c0681720>] (omap8250_irq+0x258/0x2d4)
[<c0681720>] (omap8250_irq) from [<c01a00b8>] (__handle_irq_event_percpu+0x58/0x1f0)
[<c01a00b8>] (__handle_irq_event_percpu) from [<c01a0334>] (handle_irq_event+0x68/0xcc)
[<c01a0334>] (handle_irq_event) from [<c01a4b6c>] (handle_level_irq+0xc4/0x1c8)
[<c01a4b6c>] (handle_level_irq) from [<c019f968>] (__handle_domain_irq+0x84/0xfc)
[<c019f968>] (__handle_domain_irq) from [<c0100b6c>] (__irq_svc+0x6c/0x90)
Exception stack(0xc2975d28 to 0xc2975d70)
5d20: c2532990 c25328a8 00000006 c289a015 c2532888 c2532990
5d40: 00000002 00000000 00000006 64407df7 c2532880 64407df7 00000006 c2975d78
5d60: c02ef31c c030097c 60000013 ffffffff
[<c0100b6c>] (__irq_svc) from [<c030097c>] (__d_lookup_rcu+0xbc/0x1b8)
[<c030097c>] (__d_lookup_rcu) from [<c02ef31c>] (lookup_fast+0x48/0x180)
[<c02ef31c>] (lookup_fast) from [<c02f23b8>] (walk_component+0x3c/0x1c8)
[<c02f23b8>] (walk_component) from [<c02f2780>] (link_path_walk.part.0+0x23c/0x364)
[<c02f2780>] (link_path_walk.part.0) from [<c02f28dc>] (path_parentat+0x34/0x74)
[<c02f28dc>] (path_parentat) from [<c02f48c8>] (filename_parentat+0x88/0x19c)
[<c02f48c8>] (filename_parentat) from [<c02f4a20>] (filename_create+0x44/0x150)
[<c02f4a20>] (filename_create) from [<c02f4c2c>] (do_mkdirat+0x58/0x11c)
[<c02f4c2c>] (do_mkdirat) from [<c0100080>] (ret_fast_syscall+0x0/0x58)
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On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
quoted
It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm
Cc: stable@vger.kernel.org
How far back does this need to go? What commit id does this fix? What
caused this to just show up now vs. previously?
Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
test case from Jan Kiszka that stressed UART with rapid baudrate changes
from 9600 to 4M along with data transfer.
Based on the condition that led to interrupt storm, I inferred it to
affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
idea as seen from OMAP3 regression.
Greg,
Could you please drop the patch? Very sorry for the inconvenience..
I just noticed this causes the following regression in Linux next when
pressing a key on uart console after boot at least on omap3. This seems
to happen on serial_port_in(port, UART_RX) in the quirk handling.
Vignesh, it seems this quirk needs some soc specific flag added to
it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
all the SoCs?
Yes indeed :(
I think it's best to drop this patch until the issues are resolved,
also there are some open comments above that might be answered by
limiting this quirk to a specific range of SoCs :)
Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
IP is quite different. I will respin the patch making sure, workaround
applies only to AM65x and K3 SoCs.
Regards
Vignesh
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linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
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On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
quoted
It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm
Cc: stable@vger.kernel.org
How far back does this need to go? What commit id does this fix? What
caused this to just show up now vs. previously?
Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
test case from Jan Kiszka that stressed UART with rapid baudrate changes
from 9600 to 4M along with data transfer.
Based on the condition that led to interrupt storm, I inferred it to
affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
idea as seen from OMAP3 regression.
Greg,
Could you please drop the patch? Very sorry for the inconvenience..
On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
quoted
It is possible that RX TIMEOUT is signalled after RX FIFO has been
drained, in which case a dummy read of RX FIFO is required to clear RX
TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
leading to an interrupt storm
Cc: stable@vger.kernel.org
How far back does this need to go? What commit id does this fix? What
caused this to just show up now vs. previously?
Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
test case from Jan Kiszka that stressed UART with rapid baudrate changes
from 9600 to 4M along with data transfer.
Based on the condition that led to interrupt storm, I inferred it to
affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
idea as seen from OMAP3 regression.
Greg,
Could you please drop the patch? Very sorry for the inconvenience..
quoted
I just noticed this causes the following regression in Linux next when
pressing a key on uart console after boot at least on omap3. This seems
to happen on serial_port_in(port, UART_RX) in the quirk handling.
Vignesh, it seems this quirk needs some soc specific flag added to
it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
all the SoCs?
Yes indeed :(
quoted
I think it's best to drop this patch until the issues are resolved,
also there are some open comments above that might be answered by
limiting this quirk to a specific range of SoCs :)
Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
IP is quite different. I will respin the patch making sure, workaround
applies only to AM65x and K3 SoCs.
Regards
Vignesh
What's the status here for AM65x? The issue remains present on that
platform, and I was hoping to see a quick follow up that limit the fix
to that target.
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
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Vignesh, it seems this quirk needs some soc specific flag added to
it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
all the SoCs?
Yes indeed :(
quoted
I think it's best to drop this patch until the issues are resolved,
also there are some open comments above that might be answered by
limiting this quirk to a specific range of SoCs :)
Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
IP is quite different. I will respin the patch making sure, workaround
applies only to AM65x and K3 SoCs.
Regards
Vignesh
What's the status here for AM65x? The issue remains present on that
platform, and I was hoping to see a quick follow up that limit the fix
to that target.
Sorry for the delay, I am trying to find which other TI SoCs are
affected by this issue. But that exercise will need a bit more time.
Will send a fix to address K3 SoCs like AM65x today/tomo.
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