Re: [PATCH 3/7] Input: ep93xx_keypad: Prepare clock before using it

Hello Dmitry!

On Mon, 2021-06-14 at 14:55 -0700, Dmitry Torokhov wrote:

quoted

Use clk_prepare_enable()/clk_disable_unprepare() in preparation for switch
to Common Clock Framework.

Can this be merged standalone?

In principle, yes, but I thought it would be easier if the patches
would go via the same path as CCF conversion.

quoted

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
---
  drivers/input/keyboard/ep93xx_keypad.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/keyboard/ep93xx_keypad.c b/drivers/input/keyboard/ep93xx_keypad.c
index c8194333d612..e0e931e796fa 100644
--- a/drivers/input/keyboard/ep93xx_keypad.c
+++ b/drivers/input/keyboard/ep93xx_keypad.c

@@ -157,7 +157,7 @@ static int ep93xx_keypad_open(struct input_dev *pdev)

  
        if (!keypad->enabled) {
                ep93xx_keypad_config(keypad);
-               clk_enable(keypad->clk);
+               clk_prepare_enable(keypad->clk);
                keypad->enabled = true;
        }
  

@@ -169,7 +169,7 @@ static void ep93xx_keypad_close(struct input_dev *pdev)

        struct ep93xx_keypad *keypad = input_get_drvdata(pdev);
  
        if (keypad->enabled) {
-               clk_disable(keypad->clk);
+               clk_disable_unprepare(keypad->clk);
                keypad->enabled = false;

While we are at it, I wonder about handling suspend/resume. I see that
we disable the clock even if keyboard is configured as a wakeup source.
Is it really capable of waking up the system when clock is off?

That what "EP93xx User’s Guide" says:

26.2.4 Low Power Mode
The key scanning block also supports a low power wake-up mode. In this mode, a key press
generates a wake up interrupt. The key scan interrupt should be masked. Because the wake
up interrupt is asynchronous, and depends on external keypad lines which may have a large
capacitance value, glitches may occur on the interrupt when transitioning to low power mode.
After transitioning, all clocks to the key scanning circuitry can be shut down.

-- 
Alexander Sverdlin.