On Thu, Nov 25, 2021 at 09:51:27AM +0800, allen-kh.cheng wrote:

On Wed, 2021-11-24 at 18:25 +0800, Tzung-Bi Shih wrote:

quoted

quoted

On Wed, Nov 24, 2021 at 04:45:13PM +0800, allen-kh.cheng wrote:

quoted

quoted

+static int mtk_adsp_mbox_send_data(struct mbox_chan *chan,

void

quoted

quoted

*data)
+{
+  struct adsp_mbox_ch_info *ch_info = chan->con_priv;
+  void __iomem *reg = ch_info->va_reg;
+
+  spin_lock(&ch_info->lock);
+  writel(ch_info->ipc_op_val, reg + MTK_ADSP_MBOX_IN_CMD);
+  spin_unlock(&ch_info->lock);

quoted

Why does it need the lock?

Is the write to MTK_ADSP_MBOX_IN_CMD a synchronous operation?
- If yes, I failed to understand why does it need the lock.  Every
calls to mtk_adsp_mbox_send_data() should wait for the data

transfer

quoted

completion.
- If no, I also failed to understand

why.  mtk_adsp_mbox_send_data()

quoted

has no way to be aware of the transfer completion.  Would expect a
loop for checking the completion for the case.

In ADSP MBOX IPC flow,
 
Host would call mbox send data when the shared data transfer completed.
 
(mtk_adsp_mbox_send_data will notice client using MTK_ADSP_MBOX_IN_CMD)
 
It’s more like a signal.
 
In general case,
 
There may be some hosts use the same mbox channel.
 
I think it’s better using lock to protect access to
MTK_ADSP_MBOX_IN_CMD registers

I still failed to understand.  What if 2 hosts notify the same client by writing MTK_ADSP_MBOX_IN_CMD at the same time?

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