Messages in this thread | | | Subject | Re: [PATCH v3 3/8] mailbox: Add transmit done by blocking option | From | Mikko Perttunen <> | Date | Wed, 8 Aug 2018 17:34:12 +0300 |
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On 08/08/2018 05:10 PM, Jassi Brar wrote: > On Wed, Aug 8, 2018 at 5:08 PM, Mikko Perttunen <cyndis@kapsi.fi> wrote: >> >> >> 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@nvidia.com> >>>> 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? >> > The problems arise because your hardware (SM) supports TXDONE_BY_POLL, > but your client drives it by TXDONE_BY_ACK because the older DB > channels are so. > > Please populate SM channels as a separate controller than DB. > The DB controller, as is, run by ACK method. > The SM controller should be run by polling, i.e, set txdone_poll = > true and the poll period small enough. The virtual tty client driver > should be able to safely set tx_block from appropriate context. >
Sorry, I should have clarified that I already split up the controllers. The SM controller has txdone_poll = true. I didn't adjust txpoll_period so I guess it's zero.
Mikko
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