Re: [RFC,v3 8/9] media: platform: Add Mediatek ISP P1 SCP communication

[Jungo Lin <jungo.lin@mediatek.com>]

Hi, Tomasz:

On Thu, 2019-07-25 at 19:56 +0900, Tomasz Figa wrote:
> Hi Jungo,
> 
> On Sun, Jul 21, 2019 at 11:18 AM Jungo Lin <jungo.lin@mediatek.com> wrote:
> [snip]
> > > > +           wake_up_interruptible(&isp_ctx->composer_tx_thread.wq);
> > > > +           isp_ctx->composer_tx_thread.thread = NULL;
> > > > +   }
> > > > +
> > > > +   if (isp_ctx->composer_deinit_thread.thread) {
> > > > +           wake_up(&isp_ctx->composer_deinit_thread.wq);
> > > > +           isp_ctx->composer_deinit_thread.thread = NULL;
> > > > +   }
> > > > +   mutex_unlock(&isp_ctx->lock);
> > > > +
> > > > +   pm_runtime_put_sync(&p1_dev->pdev->dev);
> > >
> > > No need to use the sync variant.
> > >
> >
> > We don't get this point. If we will call pm_runtime_get_sync in
> > mtk_isp_hw_init function, will we need to call
> > pm_runtime_put_sync_autosuspend in mtk_isp_hw_release in next patch?
> > As we know, we should call runtime pm functions in pair.
> >
> 
> My point is that pm_runtime_put_sync() is only needed if one wants the
> runtime count to be decremented after the function returns. Normally
> there is no need to do so and one would call pm_runtime_put(), or if
> autosuspend is used, pm_runtime_put_autosuspend() (note there is no
> "sync" in the name).
> 
> [snip]

Ok, got your point.
We will change to use pm_runtime_put_autosuspend() which has ASYNC flag.

> > > +static void isp_composer_handler(void *data, unsigned int len, void *priv)
> > > > +{
> > > > +   struct mtk_isp_p1_ctx *isp_ctx = (struct mtk_isp_p1_ctx *)priv;
> > > > +   struct isp_p1_device *p1_dev = p1_ctx_to_dev(isp_ctx);
> > > > +   struct device *dev = &p1_dev->pdev->dev;
> > > > +   struct mtk_isp_scp_p1_cmd *ipi_msg;
> > > > +
> > > > +   ipi_msg = (struct mtk_isp_scp_p1_cmd *)data;
> > >
> > > Should we check that len == sizeof(*ipi_msg)? (Or at least >=, if data could
> > > contain some extra bytes at the end.)
> > >
> >
> > The len parameter is the actual sending bytes from SCP to kernel.
> > In the runtime, it is only 6 bytes for isp_ack_info command
> > However, sizeof(*ipi_msg) is large due to struct mtk_isp_scp_p1_cmd is
> > union structure.
> >
> 
> That said we still should check if len is enough to cover the data
> we're accessing below.
> 

Ok, we will add the len checking before accessing the data.

> > > > +
> > > > +   if (ipi_msg->cmd_id != ISP_CMD_ACK)
> > > > +           return;
> > > > +
> > > > +   if (ipi_msg->ack_info.cmd_id == ISP_CMD_FRAME_ACK) {
> > > > +           dev_dbg(dev, "ack frame_num:%d",
> > > > +                   ipi_msg->ack_info.frame_seq_no);
> > > > +           atomic_set(&isp_ctx->composed_frame_id,
> > > > +                      ipi_msg->ack_info.frame_seq_no);
> > >
> > > I suppose we are expecting here that ipi_msg->ack_info.frame_seq_no would be
> > > just isp_ctx->composed_frame_id + 1, right? If not, we probably dropped some
> > > frames and we should handle that somehow.
> > >
> >
> > No, we use isp_ctx->composed_frame_id to save which frame sequence
> > number are composed done in SCP. In new design, we will move this from
> > isp_ctx to p1_dev.
> 
> But we compose the frames in order, don't we? Wouldn't every composed
> frame would be just previous frame ID + 1?
> 
> [snip]

Yes, we compose the frames in order.
At the same time, we already increased "frame ID + 1" in
mtk_isp_req_enqueue() for each new request before sending to SCP for
composing. After receiving the ACK from SCP, we think the frame ID is
composed done and save by isp_ctx->composed_frame_id(v3).

[RFC v3]
void mtk_isp_req_enqueue(struct device *dev, struct media_request *req)
{
	...
	frameparams.frame_seq_no = isp_ctx->frame_seq_no++;

[RFC v4]
void mtk_isp_req_enqueue(struct mtk_cam_dev *cam,
			 struct mtk_cam_dev_request *req)
{
	struct mtk_isp_p1_device *p1_dev = dev_get_drvdata(cam->dev);

	/* Accumulated frame sequence number */
	req->frame_params.frame_seq_no = ++p1_dev->enqueue_frame_seq_no;

 

> > > > +void isp_composer_hw_init(struct device *dev)
> > > > +{
> > > > +   struct mtk_isp_scp_p1_cmd composer_tx_cmd;
> > > > +   struct isp_p1_device *p1_dev = get_p1_device(dev);
> > > > +   struct mtk_isp_p1_ctx *isp_ctx = &p1_dev->isp_ctx;
> > > > +
> > > > +   memset(&composer_tx_cmd, 0, sizeof(composer_tx_cmd));
> > > > +   composer_tx_cmd.cmd_id = ISP_CMD_INIT;
> > > > +   composer_tx_cmd.frameparam.hw_module = isp_ctx->isp_hw_module;
> > > > +   composer_tx_cmd.frameparam.cq_addr.iova = isp_ctx->scp_mem_iova;
> > > > +   composer_tx_cmd.frameparam.cq_addr.scp_addr = isp_ctx->scp_mem_pa;
> > >
> > > Should we also specify the size of the buffer? Otherwise we could end up
> > > with some undetectable overruns.
> > >
> >
> > The size of SCP composer's memory is fixed to 0x200000.
> > Is it necessary to specify the size of this buffer?
> >
> > #define MTK_ISP_COMPOSER_MEM_SIZE 0x200000
> >
> > ptr = dma_alloc_coherent(p1_dev->cam_dev.smem_dev,
> >                         MTK_ISP_COMPOSER_MEM_SIZE, &addr, GFP_KERNEL);
> >
> 
> Okay, but please add a comment saying that this is an implicit
> requirement of the firmware.
> 
> Best regards,
> Tomasz

Ok, we will add comments.

Best regards,


Jungo