Re: [PATCH v3 3/8] mailbox: Add transmit done by blocking option

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On 04.08.2018 13:45, Mikko Perttunen wrote:
On 08/03/2018 03:54 PM, Jassi Brar wrote:
On Mon, Jul 2, 2018 at 5:10 PM, Mikko Perttunen <mperttunen@xxxxxxxxxx> wrote:
Add a new TXDONE option, TXDONE_BY_BLOCK. With this option, the
send_data function of the mailbox driver is expected to block until
the message has been sent. The new option is used with the Tegra
Combined UART driver to minimize unnecessary overhead when transmitting
data.

1) TXDONE_BY_BLOCK flag :-
         Have you tried setting the flag mbox_chan->mbox_client->tx_block ?

No - I suppose I should have done that. I'm a bit concerned about overhead as send_data may be called thousands of times per second, so I tried to make it as close as possible to the downstream driver that just pokes the mailbox register directly.

I tried using polling in the mailbox framework. Some printing is done from atomic context so it seems tx_block cannot be used - wait_for_completion_timeout understandably does not work in atomic context. I also tried without tx_block, in which case I got some horribly garbled output, but "Try increasing MBOX_TX_QUEUE_LEN" was readable there.

Any opinions?

Thanks,
Mikko



2) Implementing TEGRA_HSP_MBOX_TYPE_SM :-
        In mailbox framework, a controller is a collection of identical
channels. That is, instances of the same class.
        So ideally, in probe you should populate a controller for each
type of channel, i.e, DB, SM, SS and AS.

Hmm, yes, I guess this would be possible if I change the mailbox core to allow registering multiple controllers per device.

Thanks!
Mikko

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