On Thu, 2021-11-25 at 14:23 +0800, Tzung-Bi Shih wrote:

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

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

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

kh.cheng wrote:

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+static int mtk_adsp_mbox_send_data(struct

mbox_chan *chan,

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void

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*data)
+{
+  struct adsp_mbox_ch_info *ch_info = chan-

con_priv;

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+  void __iomem *reg = ch_info->va_reg;
+
+  spin_lock(&ch_info->lock);
+  writel(ch_info->ipc_op_val, reg +

MTK_ADSP_MBOX_IN_CMD);

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+  spin_unlock(&ch_info->lock);

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Why does it need the lock?

Is the write to MTK_ADSP_MBOX_IN_CMD a synchronous

operation?

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- 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

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transfer

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completion.
- If no, I also failed to understand

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why.  mtk_adsp_mbox_send_data()

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has no way to be aware of the transfer

completion.  Would

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expect a
loop for checking the completion for the case.

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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

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I still failed to understand.  What if 2 hosts notify the same

client

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by writing MTK_ADSP_MBOX_IN_CMD at the same time?

 
Hi Tzung-Bi,
 
After I think carefully. There is no need to add lock in
mtk_adsp_mbox_send_data.
 
In our dsp ipc design, we only have one host(ap) and one client(dsp).
 
If sof ip message transfer is complete, host will use mbox notice dsp
message arrived.
 
(MTK_ADSP_MBOX_IN_CMD is signal to trigger mbox irq)
 
I will remove this in next version.
 
 


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