On 4/10/23 01:08, Badhri Jagan Sridharan wrote:
On Mon, Apr 10, 2023 at 12:45 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
On Mon, Apr 10, 2023 at 07:31:34AM +0000, Badhri Jagan Sridharan wrote:
This change adds CONFIG_TCPM_LOG_WRAPAROUND which when set allows the
logs to be wrapped around. Additionally, when set, does not clear
the TCPM logs when dumped.
Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
---
drivers/usb/typec/tcpm/Kconfig | 6 ++++++
drivers/usb/typec/tcpm/tcpm.c | 9 +++++++--
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/typec/tcpm/Kconfig b/drivers/usb/typec/tcpm/Kconfig
index e6b88ca4a4b9..4dd2b594dfc9 100644
--- a/drivers/usb/typec/tcpm/Kconfig
+++ b/drivers/usb/typec/tcpm/Kconfig
@@ -18,6 +18,12 @@ config TYPEC_TCPCI
help
Type-C Port Controller driver for TCPCI-compliant controller.
+config TCPM_LOG_WRAPAROUND
+ bool "Enable TCPM log wraparound"
+ help
+ When set, wraps around TCPM logs and does not clear the logs when dumped. TCPM logs by
+ default gets cleared when dumped and does not wraparound when full.
Kconfig help text needs to be wrapped at the properly width.
I assumed that the width is 100 characters, but it looks like it is
80. Will fix it in the next version.
And you do not provide any hint here as to why this is not the default
option, or why someone would want this.
"TCPM logs by default gets cleared when dumped and does not wraparound
when full." was intended
to convey why someone would want to set this. Perhaps it's not effective.
Does the below look better:
"TCPM logs by default gets cleared when dumped and does not wraparound
when full. This can be overridden by setting this config.
When the config is set, TCPM wraps around logs and does not clear the
logs when dumped."
Also, I could make this default if that's OK with Guenter.
The reason to not wrap around the buffer was that it tends to fill up quickly
if something goes wrong. Initially I had it wrap around and often ended up
seeing endless reset sequences in the log but not the actual problem.
So, why is this not just the default operation anyway? Why would you
ever want the logs cleared?
I remember Guenter mentioning that he was finding it useful to not
wrap around the logs to fix problems
during tcpm_register_port (init sequence). IMHO wrapping around the
logs helps to triage interoperability
issues uncovered during testing. So both approaches have their own advantages.
Yes, except that "testing" at the time included connecting an arbitrary new
device to the type c port. Pretty much each of them had its own flaws.
This was also the reason for not using tracing, because I wanted to have a
log available _all_ the time, not just when explicitly enabled.
Maybe the protocol is now more stable than it used to be, and switching
to a wraparound buffer and/or to tracing makes more sense now.
I can't really say.
Guenter
Thanks for taking the time to review !
- Badhri
thanks,
greg k-h
