From a14a14595dcade4bf31e50909a6958ed2566c058 Mon Sep 17 00:00:00 2001 From: Cristian Marussi Date: Thu, 16 Sep 2021 11:33:35 +0100 Subject: [PATCH] firmware: arm_scmi: Simplify spinlocks in virtio transport Remove unneeded nested irqsave/irqrestore spinlocks. Add also a few descriptive comments to explain better the system behaviour at shutdown time. Link: https://lore.kernel.org/r/20210916103336.7243-2-cristian.marussi@arm.com Cc: "Michael S. Tsirkin" Cc: Sudeep Holla Signed-off-by: Cristian Marussi Signed-off-by: Sudeep Holla --- drivers/firmware/arm_scmi/virtio.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c index 8941bb4..f3a1ef9b 100644 --- a/drivers/firmware/arm_scmi/virtio.c +++ b/drivers/firmware/arm_scmi/virtio.c @@ -110,18 +110,16 @@ static void scmi_finalize_message(struct scmi_vio_channel *vioch, if (vioch->is_rx) { scmi_vio_feed_vq_rx(vioch, msg); } else { - unsigned long flags; - - spin_lock_irqsave(&vioch->lock, flags); + /* Here IRQs are assumed to be already disabled by the caller */ + spin_lock(&vioch->lock); list_add(&msg->list, &vioch->free_list); - spin_unlock_irqrestore(&vioch->lock, flags); + spin_unlock(&vioch->lock); } } static void scmi_vio_complete_cb(struct virtqueue *vqueue) { unsigned long ready_flags; - unsigned long flags; unsigned int length; struct scmi_vio_channel *vioch; struct scmi_vio_msg *msg; @@ -140,7 +138,8 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) goto unlock_ready_out; } - spin_lock_irqsave(&vioch->lock, flags); + /* IRQs already disabled here no need to irqsave */ + spin_lock(&vioch->lock); if (cb_enabled) { virtqueue_disable_cb(vqueue); cb_enabled = false; @@ -151,7 +150,7 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) goto unlock_out; cb_enabled = true; } - spin_unlock_irqrestore(&vioch->lock, flags); + spin_unlock(&vioch->lock); if (msg) { msg->rx_len = length; @@ -161,11 +160,18 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) scmi_finalize_message(vioch, msg); } + /* + * Release ready_lock and re-enable IRQs between loop iterations + * to allow virtio_chan_free() to possibly kick in and set the + * flag vioch->ready to false even in between processing of + * messages, so as to force outstanding messages to be ignored + * when system is shutting down. + */ spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); } unlock_out: - spin_unlock_irqrestore(&vioch->lock, flags); + spin_unlock(&vioch->lock); unlock_ready_out: spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); } @@ -435,6 +441,13 @@ static int scmi_vio_probe(struct virtio_device *vdev) static void scmi_vio_remove(struct virtio_device *vdev) { + /* + * Once we get here, virtio_chan_free() will have already been called by + * the SCMI core for any existing channel and, as a consequence, all the + * virtio channels will have been already marked NOT ready, causing any + * outstanding message on any vqueue to be ignored by complete_cb: now + * we can just stop processing buffers and destroy the vqueues. + */ vdev->config->reset(vdev); vdev->config->del_vqs(vdev); scmi_vdev = NULL; -- 2.7.4