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

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Date: Thu, 7 Mar 2024 11:21:15 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Mukesh Ojha <quic_mojha@...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 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

> 
> 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()).

Best regards,
Krzysztof