Re: [PATCH] hwmon: (aspeed-pwm-tacho) Deassert reset in probe

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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@xxxxxxxxx>

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 ?

Guenter
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