On 01.12.2022 17:49:02, Markus Schneider-Pargmann wrote: > Hi Marc, > > On Thu, Dec 01, 2022 at 10:16:05AM +0100, Marc Kleine-Budde wrote: > > On 01.12.2022 09:43:02, Markus Schneider-Pargmann wrote: > > > Hi Marc, > > > > > > On Wed, Nov 30, 2022 at 06:21:00PM +0100, Marc Kleine-Budde wrote: > > > > On 16.11.2022 21:52:55, Markus Schneider-Pargmann wrote: > > > > > Currently the driver waits to wakeup the queue until the interrupt for > > > > > the transmit event is received and acknowledged. If we want to use the > > > > > hardware FIFO, this is too late. > > > > > > > > > > Instead release the queue as soon as the transmit was transferred into > > > > > the hardware FIFO. We are then ready for the next transmit to be > > > > > transferred. > > > > > > > > If you want to really speed up the TX path, remove the worker and use > > > > the spi_async() API from the xmit callback, see mcp251xfd_start_xmit(). > > > > > > Good idea. I will check how regmap's async_write works and if it is > > > suitable to do the job. I don't want to drop the regmap usage for this > > > right now. > > > > IIRC regmap async write still uses mutexes, but sleeping is not allowed > > in the xmit handler. The mcp251xfd driver does the endianness conversion > > (and the optional CRC) manually for the TX path. > > I just saw, you can force regmap to use spinlocks as well. But it uses > the same operation for sync operations as well. But you cannot use sync SPI api under a spinlock. > > Sending directly from the xmit handler basically eliminates the queuing > > between the network stack and the worker. Getting rid of the worker > > makes life easier and it's faster anyways. > > The current implementation of the driver doesn't really queue anything > between the network stack and the worker. It is a queue of size 1 ;). Ok > To be honest I would rather focus on the other things than on getting > rid of the worker completely as this can be done in a separate patch > later as well. Yes I agree it would be nice to get rid of the worker but > it is also probably not a major bottleneck for the performance and in > its current state it works. If I have time left at the end I will be > more than happy to do that. But for the moment I would just keep the > worker as it is. Is that OK for you? Sure. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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