serial/uart_16550: Wait before setting Line Control Register (Synopsys DesignWare 8250) #37
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
lupyuen
changed the title
…s DesignWare 8250) Some UART Controllers (Synopsys DesignWare 8250) will trigger spurious interrupts when the Line Control Register (LCR) is set while the UART is busy. This patch provides the option (16550_WAIT_LCR) to wait for UART until it's not busy, before setting the LCR. (16550_WAIT_LCR is disabled by default) This patch fixes the spurious UART interrupts for the upcoming port of NuttX to StarFive JH7110 SoC (with Synopsys DesignWare 8250 UART). [The patch is explained here](https://lupyuen.github.io/articles/plic#appendix-fix-the-spurious-uart-interrupts) drivers/serial/uart_16550.c: If 16550_WAIT_LCR is enabled, wait until UART is not busy before setting LCR include/nuttx/serial/uart_16550.h: Define the UART Status Register (USR) for checking if UART is busy drivers/serial/Kconfig-16550: Added option 16550_WAIT_LCR to 16550 UART Config, disabled by default
lupyuen
pushed a commit
that referenced
this pull request
Oct 15, 2024
set CONFIG_PRIORITY_INHERITANCE=y
set CONFIG_SEM_PREALLOCHOLDERS=0 or CONFIG_SEM_PREALLOCHOLDERS=8
#24 0x4dcab71 in __assert assert/lib_assert.c:37
#25 0x4d6b0e9 in nxsem_destroyholder semaphore/sem_holder.c:602
#26 0x4d80cf7 in nxsem_destroy semaphore/sem_destroy.c:80
#27 0x4d80db9 in sem_destroy semaphore/sem_destroy.c:120
#28 0x4dcb077 in nxmutex_destroy misc/lib_mutex.c:122
#29 0x4dc6611 in pipecommon_freedev pipes/pipe_common.c:117
#30 0x4dc7fdc in pipecommon_close pipes/pipe_common.c:397
#31 0x4ed4f6d in file_close vfs/fs_close.c:78
#32 0x6a91133 in local_free local/local_conn.c:184
#33 0x6a92a9c in local_release local/local_release.c:129
#34 0x6a91d1a in local_subref local/local_conn.c:271
#35 0x6a75767 in local_close local/local_sockif.c:797
#36 0x4e978f6 in psock_close socket/net_close.c:102
#37 0x4eed1b9 in sock_file_close socket/socket.c:115
#38 0x4ed4f6d in file_close vfs/fs_close.c:78
#39 0x4ed1459 in nx_close_from_tcb inode/fs_files.c:754
#40 0x4ed1501 in nx_close inode/fs_files.c:781
#41 0x4ed154a in close inode/fs_files.c:819
#42 0x6bcb9ce in property_get kvdb/client.c:307
#43 0x6bcd465 in property_get_int32 kvdb/common.c:270
#44 0x5106c9a in tz_offset_restore app/miwear_bluetooth.c:745
#45 0x510893f in miwear_bluetooth_main app/miwear_bluetooth.c:1033
#46 0x4dcf5c8 in nxtask_startup sched/task_startup.c:70
#47 0x4d70873 in nxtask_start task/task_start.c:134
#48 0x4e04a07 in pre_start sim/sim_initialstate.c:52
Signed-off-by: ligd <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Summary
Some UART Controllers (Synopsys DesignWare 8250) will trigger spurious interrupts when the Line Control Register (LCR) is set while the UART is busy. This patch provides the option (16550_WAIT_LCR) to wait for UART until it's not busy, before setting the LCR. (16550_WAIT_LCR is disabled by default)
This patch fixes the spurious UART interrupts for the upcoming port of NuttX to StarFive JH7110 SoC (with Synopsys DesignWare 8250 UART). The patch is explained here
Modified Files
drivers/serial/uart_16550.c: If 16550_WAIT_LCR is enabled, wait until UART is not busy before setting LCRinclude/nuttx/serial/uart_16550.h: Define the UART Status Register (USR) for checking if UART is busydrivers/serial/Kconfig-16550: Added option 16550_WAIT_LCR to 16550 UART Config, disabled by defaultImpact
After applying this patch and enabling 16550_WAIT_LCR, StarFive JH7110 will boot correctly to NSH. (Instead of getting stuck servicing too many spurious UART interrupts)
No impact on existing code, since 16550_WAIT_LCR is disabled by default.
Testing
We tested this patch with the upcoming port of NuttX for JH7110. For Regression Testing, we tested with QEMU RISC-V (rv-virt:knsh64).
JH7110 Test
When 16550_WAIT_LCR is Disabled (default), JH7110 will fire spurious UART interrupts and fail to start NSH Shell (because it's too busy servicing interrupts):
When 16550_WAIT_LCR is Enabled, JH7110 will start NSH Shell correctly:
Regression Test
We tested with QEMU RISC-V (rv-virt:knsh64):
NuttX boots correctly with the default setting of 16550_WAIT_LCR (disabled):