Re: [PATCH] qcom: apr: Make apr callbacks in non-atomic context

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

Hi Andy,

Could you queue this up for 5.1 cycle!

We would need this to get the audio working on 820c along with WCD9335 
slimbus codec!

thanks,
srini

On 15/11/2018 18:49, Srinivas Kandagatla wrote:
> APR communication with DSP is not atomic in nature.
> Its request-response type. Trying to pretend that these are atomic
> and invoking apr client callbacks directly under atomic/irq context has
> endless issues with soundcard. It makes more sense to convert these
> to nonatomic calls. This also coverts all the dais to be nonatomic.
> 
> All the callbacks are now invoked as part of rx work queue.
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>   drivers/soc/qcom/apr.c | 74 +++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 69 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soc/qcom/apr.c b/drivers/soc/qcom/apr.c
> index 74f8b9607daa..8cfa825fce81 100644
> --- a/drivers/soc/qcom/apr.c
> +++ b/drivers/soc/qcom/apr.c
> @@ -8,6 +8,7 @@
>   #include <linux/spinlock.h>
>   #include <linux/idr.h>
>   #include <linux/slab.h>
> +#include <linux/workqueue.h>
>   #include <linux/of_device.h>
>   #include <linux/soc/qcom/apr.h>
>   #include <linux/rpmsg.h>
> @@ -17,8 +18,18 @@ struct apr {
>   	struct rpmsg_endpoint *ch;
>   	struct device *dev;
>   	spinlock_t svcs_lock;
> +	spinlock_t rx_lock;
>   	struct idr svcs_idr;
>   	int dest_domain_id;
> +	struct workqueue_struct *rxwq;
> +	struct work_struct rx_work;
> +	struct list_head rx_list;
> +};
> +
> +struct apr_rx_buf {
> +	struct list_head node;
> +	int len;
> +	uint8_t buf[];
>   };
>   
>   /**
> @@ -62,11 +73,7 @@ static int apr_callback(struct rpmsg_device *rpdev, void *buf,
>   				  int len, void *priv, u32 addr)
>   {
>   	struct apr *apr = dev_get_drvdata(&rpdev->dev);
> -	uint16_t hdr_size, msg_type, ver, svc_id;
> -	struct apr_device *svc = NULL;
> -	struct apr_driver *adrv = NULL;
> -	struct apr_resp_pkt resp;
> -	struct apr_hdr *hdr;
> +	struct apr_rx_buf *abuf;
>   	unsigned long flags;
>   
>   	if (len <= APR_HDR_SIZE) {
> @@ -75,6 +82,34 @@ static int apr_callback(struct rpmsg_device *rpdev, void *buf,
>   		return -EINVAL;
>   	}
>   
> +	abuf = kzalloc(sizeof(*abuf) + len, GFP_ATOMIC);
> +	if (!abuf)
> +		return -ENOMEM;
> +
> +	abuf->len = len;
> +	memcpy(abuf->buf, buf, len);
> +
> +	spin_lock_irqsave(&apr->rx_lock, flags);
> +	list_add_tail(&abuf->node, &apr->rx_list);
> +	spin_unlock_irqrestore(&apr->rx_lock, flags);
> +
> +	queue_work(apr->rxwq, &apr->rx_work);
> +
> +	return 0;
> +}
> +
> +
> +static int apr_do_rx_callback(struct apr *apr, struct apr_rx_buf *abuf)
> +{
> +	uint16_t hdr_size, msg_type, ver, svc_id;
> +	struct apr_device *svc = NULL;
> +	struct apr_driver *adrv = NULL;
> +	struct apr_resp_pkt resp;
> +	struct apr_hdr *hdr;
> +	unsigned long flags;
> +	void *buf = abuf->buf;
> +	int len = abuf->len;
> +
>   	hdr = buf;
>   	ver = APR_HDR_FIELD_VER(hdr->hdr_field);
>   	if (ver > APR_PKT_VER + 1)
> @@ -132,6 +167,23 @@ static int apr_callback(struct rpmsg_device *rpdev, void *buf,
>   	return 0;
>   }
>   
> +static void apr_rxwq(struct work_struct *work)
> +{
> +	struct apr *apr = container_of(work, struct apr, rx_work);
> +	struct apr_rx_buf *abuf, *b;
> +	unsigned long flags;
> +
> +	if (!list_empty(&apr->rx_list)) {
> +		list_for_each_entry_safe(abuf, b, &apr->rx_list, node) {
> +			apr_do_rx_callback(apr, abuf);
> +			spin_lock_irqsave(&apr->rx_lock, flags);
> +			list_del(&abuf->node);
> +			spin_unlock_irqrestore(&apr->rx_lock, flags);
> +			kfree(abuf);
> +		}
> +	}
> +}
> +
>   static int apr_device_match(struct device *dev, struct device_driver *drv)
>   {
>   	struct apr_device *adev = to_apr_device(dev);
> @@ -285,6 +337,14 @@ static int apr_probe(struct rpmsg_device *rpdev)
>   	dev_set_drvdata(dev, apr);
>   	apr->ch = rpdev->ept;
>   	apr->dev = dev;
> +	apr->rxwq = create_singlethread_workqueue("qcom_apr_rx");
> +	if (!apr->rxwq) {
> +		dev_err(apr->dev, "Failed to start Rx WQ\n");
> +		return -ENOMEM;
> +	}
> +	INIT_WORK(&apr->rx_work, apr_rxwq);
> +	INIT_LIST_HEAD(&apr->rx_list);
> +	spin_lock_init(&apr->rx_lock);
>   	spin_lock_init(&apr->svcs_lock);
>   	idr_init(&apr->svcs_idr);
>   	of_register_apr_devices(dev);
> @@ -303,6 +363,10 @@ static int apr_remove_device(struct device *dev, void *null)
>   
>   static void apr_remove(struct rpmsg_device *rpdev)
>   {
> +	struct apr *apr = dev_get_drvdata(&rpdev->dev);
> +
> +	flush_workqueue(apr->rxwq);
> +	destroy_workqueue(apr->rxwq);
>   	device_for_each_child(&rpdev->dev, NULL, apr_remove_device);
>   }
>   
>