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:
On Wed, Nov 24, 2021 at 04:45:13PM +0800, allen-kh.cheng wrote:
+static int mtk_adsp_mbox_send_data(struct mbox_chan *chan,
void
*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);
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
completion.
- If no, I also failed to understand
why. mtk_adsp_mbox_send_data()
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?