linux-kernel - Re: [PATCH] soc: qcom: llcc: Add llcc device availability check

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Date: Tue, 12 Mar 2024 21:55:08 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>
CC: <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] soc: qcom: llcc: Add llcc device availability check



On 3/7/2024 3:51 PM, Krzysztof Kozlowski wrote:
> On 20/02/2024 13:28, Mukesh Ojha wrote:
>> When llcc driver is enabled  and llcc device is not
>> physically there on the SoC, client can get
>> -EPROBE_DEFER on calling llcc_slice_getd() and it
>> is possible they defer forever.
> 
> Please wrap commit message according to Linux coding style / submission
> process (neither too early nor over the limit):
> https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/process/submitting-patches.rst#L597

Noted.

> 
>>
>> Let's add a check device availabilty and set the
>> appropriate applicable error in drv_data.
>>
>> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
>> ---
>>   drivers/soc/qcom/llcc-qcom.c | 23 ++++++++++++++++++++++-
>>   1 file changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
>> index 4ca88eaebf06..cb336b183bba 100644
>> --- a/drivers/soc/qcom/llcc-qcom.c
>> +++ b/drivers/soc/qcom/llcc-qcom.c
>> @@ -769,6 +769,27 @@ static const struct qcom_sct_config x1e80100_cfgs = {
>>   };
>>   
>>   static struct llcc_drv_data *drv_data = (void *) -EPROBE_DEFER;
>> +static DEFINE_MUTEX(dev_avail);
>> +
>> +static bool is_llcc_device_available(void)
>> +{
>> +	static struct llcc_drv_data *ptr;
>> +
>> +	mutex_lock(&dev_avail);
>> +	if (!ptr) {
>> +		struct device_node *node;
>> +
>> +		node = of_find_node_by_name(NULL, "system-cache-controller");
> 
> Why do you look names by name? This create undocumented ABI. >
> NAK (also for any future uses of such of_find_node_by_name()).

I agree, what if we add a common compatible string like qcom,llcc to all 
llcc supported SoCs.

-Mukesh
> 
> Best regards,
> Krzysztof
>