** Description changed:
+ [ Impact ]
+
+ * When adding earlycon to the kernel command line on the
+ SiFive Unmatched board the serial console will print garbage
+ halfway through booting until entering userspace and other
+ other drivers are loaded.
+
+ * The problem is the UART driver doesn't claim its clocks
+ properly so the PWM driver will turn off the parent clock
+ until PWM is needed for the LEDs on the board.
+
+ * Compiling the PWM driver as a module so it will be loaded
+ at the same time the LED drivers are loaded is a temporary
+ workaround until the following patch is backported
+ 643792048ee8 ("serial: sifive: enable clocks for UART when probed")
+
+ * Only the SoCs on the SiFive Unleashed and Unmatched boards use
+ this PWM driver, but none of them need it at boot time, so should
+ be harmless.
+
+ [ Test Plan ]
+
+ * Add earlycon and watch the serial console while booting.
+
+ * Test that PWM leds still work after the PWM driver module is loaded.
+
+ [ Where problems could occur ]
+
+ * There might be a hidden dependency on loading the PWM driver early.
+
+ [ Other Info ]
+
+ Original bug description:
+
With Kernel 5.19.0-1002-generic on the SiFive Unmatched earlyconsole
output looks like:
EFI stub: Booting Linux Kernel...
EFI stub: Using DTB from configuration table
EFI stub: Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path
EFI stub: Exiting boot services...
�������������������������������������������
With a defconfig 5.19.6 kernel this does not occr.
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https://bugs.launchpad.net/bugs/1988984
Title:
earlyconsole prints ������������������������ on 5.19.0-1002-generic
Status in linux-meta-riscv package in Ubuntu:
New
Bug description:
[ Impact ]
* When adding earlycon to the kernel command line on the
SiFive Unmatched board the serial console will print garbage
halfway through booting until entering userspace and other
other drivers are loaded.
* The problem is the UART driver doesn't claim its clocks
properly so the PWM driver will turn off the parent clock
until PWM is needed for the LEDs on the board.
* Compiling the PWM driver as a module so it will be loaded
at the same time the LED drivers are loaded is a temporary
workaround until the following patch is backported
643792048ee8 ("serial: sifive: enable clocks for UART when probed")
* Only the SoCs on the SiFive Unleashed and Unmatched boards use
this PWM driver, but none of them need it at boot time, so should
be harmless.
[ Test Plan ]
* Add earlycon and watch the serial console while booting.
* Test that PWM leds still work after the PWM driver module is
loaded.
[ Where problems could occur ]
* There might be a hidden dependency on loading the PWM driver early.
[ Other Info ]
Original bug description:
With Kernel 5.19.0-1002-generic on the SiFive Unmatched earlyconsole
output looks like:
EFI stub: Booting Linux Kernel...
EFI stub: Using DTB from configuration table
EFI stub: Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path
EFI stub: Exiting boot services...
�������������������������������������������
With a defconfig 5.19.6 kernel this does not occr.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-meta-riscv/+bug/1988984/+subscriptions
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