linux-kernel - Re: [PATCH] counter: ti-eqep: enable clock at probe

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Date: Mon, 10 Jun 2024 09:11:54 -0500
From: Judith Mendez <jm@...com>
To: David Lechner <dlechner@...libre.com>,
        William Breathitt Gray
	<wbg@...nel.org>
CC: <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] counter: ti-eqep: enable clock at probe

Hi David,

On 6/10/24 8:53 AM, David Lechner wrote:
> On 6/10/24 8:44 AM, Judith Mendez wrote:
>> Hi David,
>>
>> On 6/9/24 3:27 PM, David Lechner wrote:
>>> The TI eQEP clock is both a functional and interface clock. Since it is
>>> required for the device to function, we should be enabling it at probe.
>>>
>>> Up to now, we've just been lucky that the clock was enabled by something
>>> else on the system already.
>>>
>>> Signed-off-by: David Lechner <dlechner@...libre.com>
>>> ---
>>>    drivers/counter/ti-eqep.c | 6 ++++++
>>>    1 file changed, 6 insertions(+)
>>>
>>> diff --git a/drivers/counter/ti-eqep.c b/drivers/counter/ti-eqep.c
>>> index 072b11fd6b32..825ae22c3ebc 100644
>>> --- a/drivers/counter/ti-eqep.c
>>> +++ b/drivers/counter/ti-eqep.c
>>> @@ -6,6 +6,7 @@
>>>     */
>>>      #include <linux/bitops.h>
>>> +#include <linux/clk.h>
>>>    #include <linux/counter.h>
>>>    #include <linux/kernel.h>
>>>    #include <linux/mod_devicetable.h>
>>> @@ -376,6 +377,7 @@ static int ti_eqep_probe(struct platform_device *pdev)
>>>        struct counter_device *counter;
>>>        struct ti_eqep_cnt *priv;
>>>        void __iomem *base;
>>> +    struct clk *clk;
>>>        int err;
>>>          counter = devm_counter_alloc(dev, sizeof(*priv));
>>> @@ -415,6 +417,10 @@ static int ti_eqep_probe(struct platform_device *pdev)
>>>        pm_runtime_enable(dev);
>>>        pm_runtime_get_sync(dev);
>>>    +    clk = devm_clk_get_enabled(dev, NULL);
>>> +    if (IS_ERR(clk))
>>
>> I think it would be nice to have print here in case the we fail to get
>> the clock.
> 
> Do you mean that we should call devm_clk_get() and clk_prepare_enable()
> separately so that we get two different error messages?
> 
> The dev_err_probe() below will already print a message on any error
> (other that EPROBE_DEFER).

Apologies, I misread. The way you have it is good, thanks.

Reviewed-by: Judith Mendez <jm@...com>

> 
>>
>> ~ Judith
>>
>>> +        return dev_err_probe(dev, PTR_ERR(clk), "failed to enable clock\n");
>>> +
>>>        err = counter_add(counter);
>>>        if (err < 0) {
>>>            pm_runtime_put_sync(dev);
>>>
>>> ---
>>> base-commit: bb3f1c5fc434b0b177449f7f73ea9b112b397dd1
>>> change-id: 20240609-ti-eqep-enable-clock-91697095ca81
>>
>