linux-kernel - Re: [PATCH 2/2] remoteproc: Fix and restore the parenting hierarchy for vdev

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Date:   Tue, 17 Mar 2020 12:05:30 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suman Anna <s-anna@...com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Loic Pallardy <loic.pallardy@...com>,
        Arnaud Pouliquen <arnaud.pouliquen@...com>,
        Tero Kristo <t-kristo@...com>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] remoteproc: Fix and restore the parenting hierarchy
 for vdev

Hi Suman,

On Thu, Mar 05, 2020 at 04:41:08PM -0600, Suman Anna wrote:
> The commit 086d08725d34 ("remoteproc: create vdev subdevice with specific
> dma memory pool") has introduced a new vdev subdevice for each vdev
> declared in the firmware resource table and made it as the parent for the
> created virtio rpmsg devices instead of the previous remoteproc device.
> This changed the overall parenting hierarchy for the rpmsg devices, which
> were children of virtio devices, and does not allow the corresponding
> rpmsg drivers to retrieve the parent rproc device through the
> rproc_get_by_child() API.
> 
> Fix this by restoring the remoteproc device as the parent. The new vdev
> subdevice can continue to inherit the DMA attributes from the remoteproc's
> parent device (actual platform device).
> 
> Fixes: 086d08725d34 ("remoteproc: create vdev subdevice with specific dma memory pool")
> Signed-off-by: Suman Anna <s-anna@...com>
> ---
>  drivers/remoteproc/remoteproc_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 097f33e4f1f3..ba18f32bd0c4 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -510,7 +510,7 @@ static int rproc_handle_vdev(struct rproc *rproc, struct fw_rsc_vdev *rsc,
>  
>  	/* Initialise vdev subdevice */
>  	snprintf(name, sizeof(name), "vdev%dbuffer", rvdev->index);
> -	rvdev->dev.parent = rproc->dev.parent;
> +	rvdev->dev.parent = &rproc->dev;

I can see how it would not be possible to retrieve the parent rproc device since
rvdev->dev.parent was set to be platform device...

I wonder how the original change didn't blow up sysmon_probe() and potentially
other out-of-tree users of rproc_get_by_child().  It would be nice to have
someone from the QCOM team test your patch.

>  	rvdev->dev.dma_pfn_offset = rproc->dev.parent->dma_pfn_offset;
>  	rvdev->dev.release = rproc_rvdev_release;
>  	dev_set_name(&rvdev->dev, "%s#%s", dev_name(rvdev->dev.parent), name);

Be mindful there might be fallouts from applying this patch since it does change
the location of the vdev under /sys/device/platform/ .

Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

> -- 
> 2.23.0
>