diff mbox series

hwmon: (aspeed-pwm-tacho) Deassert reset in probe

Message ID 20171101013421.8488-1-joel@jms.id.au
State New
Headers show
Series hwmon: (aspeed-pwm-tacho) Deassert reset in probe | expand

Commit Message

Joel Stanley Nov. 1, 2017, 1:34 a.m. UTC 
The ASPEED SoC must deassert a reset in order to use the PWM/tach
peripheral.

The device tree bindings are updated to document the resets phandle, and
the example is updated to match what is expected for both the reset and
clock phandle. Note that the bindings should have always had the reset
controller, as the hardware is unusable without it.

Signed-off-by: Joel Stanley <joel@jms.id.au>

---
 .../devicetree/bindings/hwmon/aspeed-pwm-tacho.txt | 14 ++++-------
 drivers/hwmon/aspeed-pwm-tacho.c                   | 27 +++++++++++++++++++---
 2 files changed, 29 insertions(+), 12 deletions(-)

-- 
2.14.1

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Comments

Stafford Horne Nov. 1, 2017, 2:04 a.m. UTC | #1 
On Tue, Oct 31, 2017 at 06:53:15PM -0700, Guenter Roeck wrote:
> On 10/31/2017 06:34 PM, Joel Stanley wrote:

> > The ASPEED SoC must deassert a reset in order to use the PWM/tach

> > peripheral.

> > 

> > The device tree bindings are updated to document the resets phandle, and

> > the example is updated to match what is expected for both the reset and

> > clock phandle. Note that the bindings should have always had the reset

> > controller, as the hardware is unusable without it.

> > 

> > Signed-off-by: Joel Stanley <joel@jms.id.au>

> 

> Presumably the driver is being used. This change makes it incompatible with

> existing users. This is unacceptable; after all, it is possible that the

> device is taken out of reset by ROMMON or BIOS.

> 

> On top of that, the reset controller code is quite strict and issues a

> backtrace if CONFIG_RESET_CONTROLLER is not enabled. Yet, there is no

> dependency added on RESET_CONTROLLER. You might want to consider making

> the new control optional and using devm_reset_control_get_optional_exclusive().

> 

> The DT change should be a separate patch.

> 

> More comments below.


[..]

> >   	return PTR_ERR_OR_ZERO(hwmon);

> >   }

> > +static int aspeed_pwm_tacho_remove(struct platform_device *pdev)

> > +{

> > +	struct aspeed_pwm_tacho_data *priv = platform_get_drvdata(pdev);

> > +

> > +	reset_control_deassert(priv->rst);

> 

> This seems to be quite pointless. Also, did you test this code ?

> 

> > +

> > +	return 0;

> > +}

> > +

> >   static const struct of_device_id of_pwm_tacho_match_table[] = {

> >   	{ .compatible = "aspeed,ast2400-pwm-tacho", },

> >   	{ .compatible = "aspeed,ast2500-pwm-tacho", },

> > @@ -969,6 +989,7 @@ MODULE_DEVICE_TABLE(of, of_pwm_tacho_match_table);

> >   static struct platform_driver aspeed_pwm_tacho_driver = {

> >   	.probe		= aspeed_pwm_tacho_probe,

> > +	.probe		= aspeed_pwm_tacho_remove,


Also, this cant be right (should be .remove)?

> >   	.driver		= {

> >   		.name	= "aspeed_pwm_tacho",

> >   		.of_match_table = of_pwm_tacho_match_table,

> > 

> 

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Joel Stanley Nov. 1, 2017, 6:59 a.m. UTC | #2 
On Wed, Nov 1, 2017 at 12:44 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On 10/31/2017 07:04 PM, Stafford Horne wrote:

>>

>> On Tue, Oct 31, 2017 at 06:53:15PM -0700, Guenter Roeck wrote:

>>>

>>> On 10/31/2017 06:34 PM, Joel Stanley wrote:

>>>>

>>>> The ASPEED SoC must deassert a reset in order to use the PWM/tach

>>>> peripheral.

>>>>

>>>> The device tree bindings are updated to document the resets phandle, and

>>>> the example is updated to match what is expected for both the reset and

>>>> clock phandle. Note that the bindings should have always had the reset

>>>> controller, as the hardware is unusable without it.

>>>>

>>>> Signed-off-by: Joel Stanley <joel@jms.id.au>

>>>

>>>

>>> Presumably the driver is being used. This change makes it incompatible

>>> with

>>> existing users. This is unacceptable; after all, it is possible that the

>>> device is taken out of reset by ROMMON or BIOS.

>>>

>>> On top of that, the reset controller code is quite strict and issues a

>>> backtrace if CONFIG_RESET_CONTROLLER is not enabled. Yet, there is no

>>> dependency added on RESET_CONTROLLER. You might want to consider making

>>> the new control optional and using

>>> devm_reset_control_get_optional_exclusive().

>>>

>>> The DT change should be a separate patch.

>>>

>>> More comments below.

>>

>>

>> [..]

>>

>>>>         return PTR_ERR_OR_ZERO(hwmon);

>>>>    }

>>>> +static int aspeed_pwm_tacho_remove(struct platform_device *pdev)

>>>> +{

>>>> +       struct aspeed_pwm_tacho_data *priv = platform_get_drvdata(pdev);

>>>> +

>>>> +       reset_control_deassert(priv->rst);

>>>

>>>

>>> This seems to be quite pointless. Also, did you test this code ?

>>>

>>>> +

>>>> +       return 0;

>>>> +}

>>>> +

>>>>    static const struct of_device_id of_pwm_tacho_match_table[] = {

>>>>         { .compatible = "aspeed,ast2400-pwm-tacho", },

>>>>         { .compatible = "aspeed,ast2500-pwm-tacho", },

>>>> @@ -969,6 +989,7 @@ MODULE_DEVICE_TABLE(of, of_pwm_tacho_match_table);

>>>>    static struct platform_driver aspeed_pwm_tacho_driver = {

>>>>         .probe          = aspeed_pwm_tacho_probe,

>>>> +       .probe          = aspeed_pwm_tacho_remove,

>>

>>

>> Also, this cant be right (should be .remove)?

>>

>

> Nice. Makes me really wonder what this code would do. Does this even compile

> ?


It compiled. And booted, but it didn't do much :) I rushed sending out
the patch a bit, sorry.

I've spent today I did some closer testing with a fixed v2 and I do
get values out of the device. I don't have access to a machine that I
can see the fans spinning on, so it's hard to know if the values are
correct. I'll send it out tomorrow with a request for testing.

Cheers,

Joel
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diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt b/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
index 367c8203213b..3ac02988a1a5 100644
--- a/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
+++ b/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
@@ -22,8 +22,9 @@  Required properties for pwm-tacho node:
 - compatible : should be "aspeed,ast2400-pwm-tacho" for AST2400 and
 	       "aspeed,ast2500-pwm-tacho" for AST2500.
 
-- clocks : a fixed clock providing input clock frequency(PWM
-	   and Fan Tach clock)
+- clocks : phandle to clock provider with the clock number in the second cell
+
+- resets : phandle to reset controller with the reset number in the second cell
 
 fan subnode format:
 ===================
@@ -48,19 +49,14 @@  Required properties for each child node:
 
 Examples:
 
-pwm_tacho_fixed_clk: fixedclk {
-	compatible = "fixed-clock";
-	#clock-cells = <0>;
-	clock-frequency = <24000000>;
-};
-
 pwm_tacho: pwmtachocontroller@1e786000 {
 	#address-cells = <1>;
 	#size-cells = <1>;
 	#cooling-cells = <2>;
 	reg = <0x1E786000 0x1000>;
 	compatible = "aspeed,ast2500-pwm-tacho";
-	clocks = <&pwm_tacho_fixed_clk>;
+	clocks = <&syscon ASPEED_CLK_APB>;
+	resets = <&syscon ASPEED_RESET_PWM>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;
 
diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c
index f914e5f41048..346a4c5952a3 100644
--- a/drivers/hwmon/aspeed-pwm-tacho.c
+++ b/drivers/hwmon/aspeed-pwm-tacho.c
@@ -7,19 +7,20 @@ 
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/gpio/consumer.h>
-#include <linux/delay.h>
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/of_platform.h>
 #include <linux/of_device.h>
+#include <linux/of_platform.h>
 #include <linux/platform_device.h>
-#include <linux/sysfs.h>
 #include <linux/regmap.h>
+#include <linux/reset.h>
+#include <linux/sysfs.h>
 #include <linux/thermal.h>
 
 /* ASPEED PWM & FAN Tach Register Definition */
@@ -181,6 +182,7 @@  struct aspeed_cooling_device {
 
 struct aspeed_pwm_tacho_data {
 	struct regmap *regmap;
+	struct reset_control *rst;
 	unsigned long clk_freq;
 	bool pwm_present[8];
 	bool fan_tach_present[16];
@@ -931,6 +933,15 @@  static int aspeed_pwm_tacho_probe(struct platform_device *pdev)
 			&aspeed_pwm_tacho_regmap_config);
 	if (IS_ERR(priv->regmap))
 		return PTR_ERR(priv->regmap);
+
+	priv->rst = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(priv->rst)) {
+		dev_err(dev,
+			"missing or invalid reset controller device tree entry");
+		return PTR_ERR(priv->rst);
+	}
+	reset_control_deassert(priv->rst);
+
 	regmap_write(priv->regmap, ASPEED_PTCR_TACH_SOURCE, 0);
 	regmap_write(priv->regmap, ASPEED_PTCR_TACH_SOURCE_EXT, 0);
 
@@ -960,6 +971,15 @@  static int aspeed_pwm_tacho_probe(struct platform_device *pdev)
 	return PTR_ERR_OR_ZERO(hwmon);
 }
 
+static int aspeed_pwm_tacho_remove(struct platform_device *pdev)
+{
+	struct aspeed_pwm_tacho_data *priv = platform_get_drvdata(pdev);
+
+	reset_control_deassert(priv->rst);
+
+	return 0;
+}
+
 static const struct of_device_id of_pwm_tacho_match_table[] = {
 	{ .compatible = "aspeed,ast2400-pwm-tacho", },
 	{ .compatible = "aspeed,ast2500-pwm-tacho", },
@@ -969,6 +989,7 @@  MODULE_DEVICE_TABLE(of, of_pwm_tacho_match_table);
 
 static struct platform_driver aspeed_pwm_tacho_driver = {
 	.probe		= aspeed_pwm_tacho_probe,
+	.probe		= aspeed_pwm_tacho_remove,
 	.driver		= {
 		.name	= "aspeed_pwm_tacho",
 		.of_match_table = of_pwm_tacho_match_table,