Documentation/admin-guide: kernel-parameters: Update nohlt section

Update the documentation regarding "nohlt" and indicate that it is not
only for bugs, but can be useful to disable the architecture specific
sleep instructions. ARM, ARM64, SuperH and Microblaze all use
CONFIG_GENERIC_IDLE_POLL_SETUP which takes care of honoring the
"hlt"/"nohlt" parameters.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20210209172349.2249596-1-f.fainelli@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 50d9b9bfcd6e22fc60bc27d1e3ddcd92b9946ca1..e938ccf3dad31a667b301afbb174a5ad4b8677ed 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3266,9 +3266,14 @@
                        parameter, xsave area per process might occupy more
                        memory on xsaves enabled systems.
 
-       nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
-                       wfi(ARM) instruction doesn't work correctly and not to
-                       use it. This is also useful when using JTAG debugger.
+       nohlt           [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
+                       in do_idle() and not use the arch_cpu_idle()
+                       implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
+                       to be effective. This is useful on platforms where the
+                       sleep(SH) or wfi(ARM,ARM64) instructions do not work
+                       correctly or when doing power measurements to evalute
+                       the impact of the sleep instructions. This is also
+                       useful when using JTAG debugger.
 
        no_file_caps    Tells the kernel not to honor file capabilities.  The
                        only way then for a file to be executed with privilege