linux-kernel - Re: [PATCH 1/2] soc: qcom: smsm: Handle probe deferral

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Date:   Mon, 27 Mar 2017 23:18:29 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Jonathan Neusch?fer <j.neuschaefer@....net>
Cc:     linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] soc: qcom: smsm: Handle probe deferral

On Wed 15 Mar 04:43 PDT 2017, Jonathan Neusch?fer wrote:

> If qcom_smem_get or qcom_smem_alloc return -EPROBE_DEFER, let the caller
> the caller handle it, instead of treating it as an error.
> 
> Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@....net>
> 
> ---
> v1:
> - TODO: Reading qcom_smsm_probe, I noticed memory leaks in error paths:
>   smsm, smsm->entries, etc. are allocated (with devm_kzalloc), but not
>   freed when the function returns early. This should be addressed at
>   some point (in a separate patch).
> ---
>  drivers/soc/qcom/smsm.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/qcom/smsm.c b/drivers/soc/qcom/smsm.c
> index d0337b2a71c8..3918645e5708 100644
> --- a/drivers/soc/qcom/smsm.c
> +++ b/drivers/soc/qcom/smsm.c
> @@ -439,7 +439,9 @@ static int smsm_get_size_info(struct qcom_smsm *smsm)
>  	} *info;
>  
>  	info = qcom_smem_get(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SIZE_INFO, &size);
> -	if (PTR_ERR(info) == -ENOENT || size != sizeof(*info)) {
> +	if (PTR_ERR(info) == -EPROBE_DEFER) {
> +		return PTR_ERR(info);
> +	} else if (PTR_ERR(info) == -ENOENT || size != sizeof(*info)) {

The following elseif was supposed to take care of this case, but I
clearly screwed this up.

Rather than adding a special case for EPROBE_DEFER before the two checks
and then fix up the original expression to make errors fall back to the
original else, I think you should rearrange the conditionals.

Probably better to write it like this instead:

        if (IS_ERR(info) && PTR_ERR(info) != -ENOENT) {
                if (PTR_ERR(info) != -EPROBE_DEFER)
                        dev_err(smsm->dev, "unable to retrieve smsm size info\n");
                return PTR_ERR(info);
        } else if (IS_ERR(info) || size != sizeof(*info)) {
                dev_warn(smsm->dev, "no smsm size info, using defaults\n");
                smsm->num_entries = SMSM_DEFAULT_NUM_ENTRIES;
                smsm->num_hosts = SMSM_DEFAULT_NUM_HOSTS;
                return 0;
        }

>  		dev_warn(smsm->dev, "no smsm size info, using defaults\n");
>  		smsm->num_entries = SMSM_DEFAULT_NUM_ENTRIES;
>  		smsm->num_hosts = SMSM_DEFAULT_NUM_HOSTS;
> @@ -515,7 +517,9 @@ static int qcom_smsm_probe(struct platform_device *pdev)
>  	/* Acquire the main SMSM state vector */
>  	ret = qcom_smem_alloc(QCOM_SMEM_HOST_ANY, SMEM_SMSM_SHARED_STATE,
>  			      smsm->num_entries * sizeof(u32));
> -	if (ret < 0 && ret != -EEXIST) {
> +	if (ret == -EPROBE_DEFER) {
> +		return ret;
> +	} else if (ret < 0 && ret != -EEXIST) {

The idiomatic way to write this is:

if (ret < 0 && ret != -EEXIST) {
	if (ret != -EPROBE_DEFER)
		dev_err();
	return ret;
}

However, for us to reach this point in smsm_probe() the above
qcom_smem_get() must have returned successfully, i.e. we have SMEM in
place so there's no need to handle this case specifically.

>  		dev_err(&pdev->dev, "unable to allocate shared state entry\n");
>  		return ret;
>  	}

Regards,
Bjorn