[PATCH v7 3/6] dt-bindings: mailbox: imx-mu: add generic MU channel support

On Tue, Jul 31, 2018 at 3:45 PM, Jassi Brar [off-list ref] wrote:

On Tue, Jul 31, 2018 at 12:51 PM, A.s. Dong [off-list ref] wrote:

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Hi Jassi,

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However, if SCU (in its current form) must be supported. We may need
to add the third cell (irq enable or not) or some better way, right
now.

Looking at imx_mu_scu_send_data(), which simply polls on the tx, I think we
don't even need third cell for scu client. A simple 2-cell, 8 uni-dir channel
setup should work.

How would you suggest to use for SCU in 2 -cells?

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If I see the scu client driver, I could confirm how it would work.

I've already given a general overview from here:
https://www.spinics.net/lists/arm-kernel/msg669202.html

No, that is controller side code.

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Do you need me to send the full scu client driver patch for the reference?
If yes, please feel free to let me know.

Yes, that'll make it clearer.

Thanks for sharing the patch offline.

I don't see why it can't be adapted to work with the simple 2-cell
implementation. Instead of one virtual, ask for 4 physical channels
and send data in u32 chunks sequentially over them.
In fact, that should make it even better by removing the tight-loop
(zero delay!!) polling in send_data() -- MU does support interrupts,
why not use them to avoid polling?  If you find it hard, I can make a
patch on top of your client patchset, once Oleksij is done with the MU
driver.

I have some more suggestions for the client driver. But since I don't
have to live with them (you do), I can't demand you make those
changes. If you like, please feel free to cc me on the next revision
of the client driver.