linux-kernel - Re: [RFC PATCH v2 10/10] firmware: arm

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Date:   Thu, 8 Apr 2021 09:15:28 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Peter Hilber <peter.hilber@...nsynergy.com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        DTML <devicetree@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org,
        Igor Skalkin <igor.skalkin@...nsynergy.com>,
        Rob Herring <robh+dt@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        souvik.chakravarty@....com, alex.bennee@...aro.org,
        jean-philippe@...aro.org, mikhail.golubev@...nsynergy.com,
        anton.yakovlev@...nsynergy.com,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [RFC PATCH v2 10/10] firmware: arm_scmi: Add virtio transport

On Fri, Nov 6, 2020 at 2:59 AM Peter Hilber
<peter.hilber@...nsynergy.com> wrote:

> +static int scmi_vio_probe(struct virtio_device *vdev)
> +{
> +       struct device *dev = &vdev->dev;
> +       struct scmi_vio_channel **vioch;
> +       bool have_vq_rx;
> +       int vq_cnt;
> +       int i;
> +       struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
> +
> +       vioch = devm_kcalloc(dev, VIRTIO_SCMI_VQ_MAX_CNT, sizeof(*vioch),
> +                            GFP_KERNEL);
> +       if (!vioch)
> +               return -ENOMEM;
> +
> +       have_vq_rx = virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);
> +       vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
> +
> +       for (i = 0; i < vq_cnt; i++) {
> +               vioch[i] = devm_kzalloc(dev, sizeof(**vioch), GFP_KERNEL);
> +               if (!vioch[i])
> +                       return -ENOMEM;
> +       }
> +
> +       if (have_vq_rx)
> +               vioch[VIRTIO_SCMI_VQ_RX]->is_rx = true;
> +
> +       if (virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks,
> +                           scmi_vio_vqueue_names, NULL)) {
> +               dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt);
> +               return -1;
> +       }
> +       dev_info(dev, "Found %d virtqueue(s)\n", vq_cnt);
> +
> +       for (i = 0; i < vq_cnt; i++) {
> +               spin_lock_init(&vioch[i]->lock);
> +               vioch[i]->vqueue = vqs[i];
> +               vioch[i]->vqueue->priv = vioch[i];

The vqueue->priv field is used by core, you can't update it else
notifications won't work.

> +       }
> +
> +       vdev->priv = vioch;
> +
> +       virtio_device_ready(vdev);
> +
> +       return 0;
> +}

diff --git a/drivers/firmware/arm_scmi/virtio.c
b/drivers/firmware/arm_scmi/virtio.c
index f70aa72f34f1..b1af77341b30 100644
--- a/drivers/firmware/arm_scmi/virtio.c
+++ b/drivers/firmware/arm_scmi/virtio.c
@@ -80,7 +80,8 @@ static int scmi_vio_populate_vq_rx(struct
scmi_vio_channel *vioch,

 static void scmi_vio_complete_cb(struct virtqueue *vqueue)
 {
-       struct scmi_vio_channel *vioch = vqueue->priv;
+       struct scmi_vio_channel **_vioch = vqueue->vdev->priv;
+       struct scmi_vio_channel *vioch = _vioch[vqueue->index];
        unsigned long iflags;
        unsigned int length;

@@ -454,7 +455,6 @@ static int scmi_vio_probe(struct virtio_device *vdev)
        for (i = 0; i < vq_cnt; i++) {
                spin_lock_init(&vioch[i]->lock);
                vioch[i]->vqueue = vqs[i];
-               vioch[i]->vqueue->priv = vioch[i];
        }

        vdev->priv = vioch;