[v4,28/68] clk: imx: scu: Add a determine_rate hook

Commit Message

Maxime Ripard May 5, 2023, 11:25 a.m. UTC

The iMX SCU mux clock implements a mux with a set_parent hook, but
doesn't provide a determine_rate implementation.

This is a bit odd, since set_parent() is there to, as its name implies,
change the parent of a clock. However, the most likely candidates to
trigger that parent change are either the assigned-clock-parents device
tree property or a call to clk_set_rate(), with determine_rate()
figuring out which parent is the best suited for a given rate.

The other trigger would be a call to clk_set_parent(), but it's far less
used, and it doesn't look like there's any obvious user for that clock.

Similarly, it doesn't look like the device tree using that clock driver
uses any of the assigned-clock properties on that clock.

So, the set_parent hook is effectively unused, possibly because of an
oversight. However, it could also be an explicit decision by the
original author to avoid any reparenting but through an explicit call to
clk_set_parent().

The latter case would be equivalent to setting the determine_rate
implementation to clk_hw_determine_rate_no_reparent(). Indeed, if no
determine_rate implementation is provided, clk_round_rate() (through
clk_core_round_rate_nolock()) will call itself on the parent if
CLK_SET_RATE_PARENT is set, and will not change the clock rate
otherwise.

And if it was an oversight, then we are at least explicit about our
behavior now and it can be further refined down the line.

Cc: Abel Vesa <[e-mail]>
Cc: Fabio Estevam <[e-mail]>
Cc: Peng Fan <[e-mail]>
Cc: Sascha Hauer <[e-mail]>
Cc: Shawn Guo <[e-mail]>
Cc: [e-mail]
Cc: NXP Linux Team <[e-mail]>
Cc: Pengutronix Kernel Team <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>
---
 drivers/clk/imx/clk-scu.c | 1 +
 1 file changed, 1 insertion(+)

Comments

kernel test robot May 6, 2023, 12:37 a.m. UTC | #1

Hi Maxime,

kernel test robot noticed the following build errors:

[auto build test ERROR on 145e5cddfe8b4bf607510b2dcf630d95f4db420f]

url:    https://github.com/intel-lab-lkp/linux/commits/Maxime-Ripard/clk-Export-clk_hw_forward_rate_request/20230505-193724
base:   145e5cddfe8b4bf607510b2dcf630d95f4db420f
patch link:    https://lore.kernel.org/r/20221018-clk-range-checks-fixes-v4-28-971d5077e7d2%40cerno.tech
patch subject: [PATCH v4 28/68] clk: imx: scu: Add a determine_rate hook
config: arm-allmodconfig (https://download.01.org/0day-ci/archive/20230506/[e-mail]/config)
compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/0c9c183066c25a7519ff60578753e40bf622b982
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Maxime-Ripard/clk-Export-clk_hw_forward_rate_request/20230505-193724
        git checkout 0c9c183066c25a7519ff60578753e40bf622b982
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[e-mail]>
| Link: https://lore.kernel.org/oe-kbuild-all/[e-mail]/

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/imx/clk-imx-scu.ko] undefined!
ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/clk_test.ko] undefined!
ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/clk-cdce706.ko] undefined!
ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/clk-lochnagar.ko] undefined!
ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/clk-si5341.ko] undefined!
ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/clk-versaclock5.ko] undefined!
ERROR: modpost: "clk_hw_determine_rate_no_reparent" [drivers/clk/clk-wm831x.ko] undefined!

Patch

diff --git a/drivers/clk/imx/clk-scu.c b/drivers/clk/imx/clk-scu.c
index 1e6870f3671f..417f893f8895 100644
--- a/drivers/clk/imx/clk-scu.c
+++ b/drivers/clk/imx/clk-scu.c
@@ -785,6 +785,7 @@  static int clk_gpr_mux_scu_set_parent(struct clk_hw *hw, u8 index)
 }
 
 static const struct clk_ops clk_gpr_mux_scu_ops = {
+	.determine_rate = clk_hw_determine_rate_no_reparent,
 	.get_parent = clk_gpr_mux_scu_get_parent,
 	.set_parent = clk_gpr_mux_scu_set_parent,
 };