scripts/gdb: bail early if there are no clocks

Avoid generating an exception if there are no clocks registered:

(gdb) lx-clk-summary
enable prepare protect
clock count count count rate
------------------------------------------------------------------------
Python Exception <class 'gdb.error'>: No symbol "clk_root_list" in
current context.
Error occurred in Python: No symbol "clk_root_list" in current context.

Link: https://lkml.kernel.org/r/20230323225246.3302977-1-f.fainelli@gmail.com
Fixes: d1e9710b63d8 ("scripts/gdb: initial clk support: lx-clk-summary")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Leonard Crestez <leonard.crestez@nxp.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/gdb: print cached rate in lx-clk-summary

The clk rate is always stored in clk_core but might be out of date and
require calls to update from hardware.

Deal with that case by printing a (c) suffix.

Link: http://lkml.kernel.org/r/1a474318982a5f0125f2360c4161029b17f56bd1.1556881728.git.leonard.crestez@nxp.com
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/gdb: add $lx_clk_core_lookup function

Finding an individual clk_core requires walking the tree which can be
quite complicated so add a helper for easy access.

(gdb) print *(struct clk_scu*)$lx_clk_core_lookup("uart0_clk")->hw

Link: http://lkml.kernel.org/r/Message-ID:
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/gdb: initial clk support: lx-clk-summary

Add an lx-clk-summary command which prints a subset of
/sys/kernel/debug/clk/clk_summary.

This can be used to examine hangs caused by clk not being enabled.

Link: http://lkml.kernel.org/r/Message-ID:
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>