Re: [PATCH v3 2/3] Input: snvs_pwrkey - enable snvs clock as needed

Hi Dmitry,

On 20-07-29 23:04, Dmitry Torokhov wrote:

On Wed, Jul 29, 2020 at 09:33:23AM +0200, Marco Felsch wrote:

quoted

Hi,

On 20-07-23 10:43, Horia Geantă wrote:

quoted

From: André Draszik <redacted>

At the moment, enabling this driver without the SNVS RTC driver
being active will hang the kernel as soon as the power button
is pressed.

The reason is that in that case the SNVS isn't enabled, and
any attempt to read the SNVS registers will simply hang forever.

Ensure the clock is enabled (during the interrupt handler) to
make this driver work.

Also see commit 7f8993995410 ("drivers/rtc/rtc-snvs: add clock support")
and commit edb190cb1734
("rtc: snvs: make sure clock is enabled for interrupt handle")
for similar updates to the snvs rtc driver.

Signed-off-by: André Draszik <redacted>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
---
 drivers/input/keyboard/snvs_pwrkey.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/input/keyboard/snvs_pwrkey.c b/drivers/input/keyboard/snvs_pwrkey.c
index 2f5e3ab5ed63..382d2ae82c9b 100644
--- a/drivers/input/keyboard/snvs_pwrkey.c
+++ b/drivers/input/keyboard/snvs_pwrkey.c

@@ -16,6 +16,7 @@
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/pm_wakeirq.h>
+#include <linux/clk.h>
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
 

@@ -38,6 +39,7 @@ struct pwrkey_drv_data {
 	int wakeup;
 	struct timer_list check_timer;
 	struct input_dev *input;
+	struct clk *clk;
 	u8 minor_rev;
 };
 

@@ -47,7 +49,10 @@ static void imx_imx_snvs_check_for_events(struct timer_list *t)
 	struct input_dev *input = pdata->input;
 	u32 state;
 
+	clk_enable(pdata->clk);
 	regmap_read(pdata->snvs, SNVS_HPSR_REG, &state);
+	clk_disable(pdata->clk);
+
 	state = state & SNVS_HPSR_BTN ? 1 : 0;
 
 	/* only report new event if status changed */

@@ -74,11 +79,13 @@ static irqreturn_t imx_snvs_pwrkey_interrupt(int irq, void *dev_id)
 
 	pm_wakeup_event(input->dev.parent, 0);
 
+	clk_enable(pdata->clk);
+
 	regmap_read(pdata->snvs, SNVS_LPSR_REG, &lp_status);
 	if (lp_status & SNVS_LPSR_SPO) {
 		if (pdata->minor_rev == 0) {
 			/*
-			 * The first generation i.MX6 SoCs only sends an
+			 * The first generation i.MX[6|7] SoCs only send an
 			 * interrupt on button release. To mimic power-key
 			 * usage, we'll prepend a press event.
 			 */

@@ -96,6 +103,8 @@ static irqreturn_t imx_snvs_pwrkey_interrupt(int irq, void *dev_id)
 	/* clear SPO status */
 	regmap_write(pdata->snvs, SNVS_LPSR_REG, SNVS_LPSR_SPO);
 
+	clk_disable(pdata->clk);

I'm not so happy about clk_enable/disable() during the interrupt
routine since those routines should be handled fast. Since we assume
that the clock is always oni

We do? I thought that the fact that clock might be off is the root of
the problem.

Currently yes else the driver would never work. I thought so at least
after reading the commit message. But after checking the imx6qdl I
found that the imx6qdl has no clock-gate for the SNVS module. I think
Horia had Problems on a imx7 device since he adapted the comment to
cover the imx7. Which makes more sense since the imx7 has a clock gate
but the commit message is wrong. After checking the device-tree's in
mainline all imx7 and imx8 devices specify the "snvs-pwrkey" clock so
this is a new feature and they need the clock. So IMHO for those devices
a clock should be required and not optional.

quoted

I would rather call clk_prepare_enable()
during probe() and keep the clock on.

clk_enable() must not sleep and is supposed to be lightweight. This
interrupt I believe is supposed to be infrequent, so having it here
should be fine and might save us some power.

Didn't know that clk_enable()/clk_disable() never sleeps and yes it
should be infrequent triggered. I don't think that we can save a
measureable amount of power since this is Low-Power IP clocked by a
low-power clock. However, this was just my point of view.

quoted

quoted

+
 	return IRQ_HANDLED;
 }
 

@@ -140,6 +149,23 @@ static int imx_snvs_pwrkey_probe(struct platform_device *pdev)
 	if (pdata->irq < 0)
 		return -EINVAL;
 
+	pdata->clk = devm_clk_get_optional(&pdev->dev, "snvs-pwrkey");
+	if (IS_ERR(pdata->clk))
+		return PTR_ERR(pdata->clk);
+
+	error = clk_prepare(pdata->clk);
+	if (error) {
+		dev_err(&pdev->dev, "failed to prepare the snvs clock\n");
+		return error;
+	}
+	error = devm_add_action_or_reset(&pdev->dev,
+			(void(*)(void *))clk_unprepare,
+			pdata->clk);

I'm not a fan about those casts. However, the intentation should be
fixed.

Yes, can we please create a proper function for this (or maybe we will
finally get devm clk API?).

devm_clk API +1 :)

Regards,
  Marco