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

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Date: Mon, 10 Jun 2024 08:53:35 -0500
From: David Lechner <dlechner@...libre.com>
To: Judith Mendez <jm@...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

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).

> 
> ~ 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
>