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Message-ID: <d617c991-b7a7-eb8f-0747-303c33cbf9a7@quicinc.com>
Date: Mon, 26 Feb 2024 16:02:33 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Sahil Chandna <quic_chandna@...cinc.com>, <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 2/22/2024 11:37 PM, Sahil Chandna wrote:
> On 2/20/2024 5:58 PM, 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.
>>
>> 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);
> what is the requirement for mutex lock here? Since we are only trying to
> find if node present or not
I was trying to avoid two parallel call from llcc_slice_getd() calling
parallel call to of_find_node_by_name() as it should be one time search
for device presence to find a node and check if device is present or
not.
-Mukesh
>> +
>> +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");
>> + if (!of_device_is_available(node)) {
>> + pr_warn("llcc-qcom: system-cache-controller node not
>> found\n");
>> + drv_data = ERR_PTR(-ENODEV);
>> + }
>> + of_node_put(node);
>> + ptr = drv_data;
>> + }
>> + mutex_unlock(&dev_avail);
>> + return (PTR_ERR(ptr) != -ENODEV) ? true : false;
>> +}
>> /**
>> * llcc_slice_getd - get llcc slice descriptor
>> @@ -783,7 +804,7 @@ struct llcc_slice_desc *llcc_slice_getd(u32 uid)
>> struct llcc_slice_desc *desc;
>> u32 sz, count;
>> - if (IS_ERR(drv_data))
>> + if (!is_llcc_device_available() || IS_ERR(drv_data))
>> return ERR_CAST(drv_data);
>> cfg = drv_data->cfg;
>
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