linux-kernel - Re: [PATCH 09/14] rpmsg: qcom_smd: Use qcom_smem_is

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Date:   Mon, 5 Jun 2023 20:56:44 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Stephan Gerhold <stephan@...hold.net>,
        Bjorn Andersson <andersson@...nel.org>
Cc:     Andy Gross <agross@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH 09/14] rpmsg: qcom_smd: Use qcom_smem_is_available()



On 5.06.2023 09:08, Stephan Gerhold wrote:
> Rather than looking up a dummy item from SMEM, use the new
> qcom_smem_is_available() function to make the code more clear
> (and reduce the overhead slightly).
> 
> Add the same check to qcom_smd_register_edge() as well to ensure that
> it only succeeds if SMEM is already available - if a driver calls the
> function and SMEM is not available yet then the initial state will be
> read incorrectly and the RPMSG devices might never become available.
> 
> Signed-off-by: Stephan Gerhold <stephan@...hold.net>
> ---
>  drivers/rpmsg/qcom_smd.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/rpmsg/qcom_smd.c b/drivers/rpmsg/qcom_smd.c
> index 7b9c298aa491..43f601c84b4f 100644
> --- a/drivers/rpmsg/qcom_smd.c
> +++ b/drivers/rpmsg/qcom_smd.c
> @@ -1479,6 +1479,9 @@ struct qcom_smd_edge *qcom_smd_register_edge(struct device *parent,
>  	struct qcom_smd_edge *edge;
>  	int ret;
>  
> +	if (!qcom_smem_is_available())
> +		return ERR_PTR(-EPROBE_DEFER);
> +
>  	edge = kzalloc(sizeof(*edge), GFP_KERNEL);
>  	if (!edge)
>  		return ERR_PTR(-ENOMEM);
> @@ -1553,12 +1556,9 @@ EXPORT_SYMBOL(qcom_smd_unregister_edge);
>  static int qcom_smd_probe(struct platform_device *pdev)
>  {
>  	struct device_node *node;
> -	void *p;
>  
> -	/* Wait for smem */
> -	p = qcom_smem_get(QCOM_SMEM_HOST_ANY, smem_items[0].alloc_tbl_id, NULL);
> -	if (PTR_ERR(p) == -EPROBE_DEFER)
> -		return PTR_ERR(p);
> +	if (!qcom_smem_is_available())
> +		return -EPROBE_DEFER;
>  
>  	for_each_available_child_of_node(pdev->dev.of_node, node)
>  		qcom_smd_register_edge(&pdev->dev, node);
Hm.. we're not checking the return value here, at all.. Perhaps that
could be improved and we could only check for smem presence inside
qcom_smd_register_edge()?

Konrad
>