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Date: Wed, 1 Nov 2017 17:29:31 +1030 From: Joel Stanley <joel@....id.au> To: Guenter Roeck <linux@...ck-us.net> Cc: Stafford Horne <shorne@...il.com>, Rob Herring <robh+dt@...nel.org>, Philipp Zabel <philipp.zabel@...il.com>, Mykola Kostenok <c_mykolak@...lanox.com>, Jaghathiswari Rankappagounder Natarajan <jaghu@...gle.com>, devicetree <devicetree@...r.kernel.org>, linux-hwmon@...r.kernel.org, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] hwmon: (aspeed-pwm-tacho) Deassert reset in probe On Wed, Nov 1, 2017 at 12:44 PM, Guenter Roeck <linux@...ck-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@....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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