On Wed, Aug 8, 2018 at 5:08 PM, Mikko Perttunen <cyndis@xxxxxxxx> 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@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? > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
