On 03.05.2022 16:32:32, Andrew Dennison wrote: > > > When value is configurable then for (uncommon) number > > > of buffers which is not power of two, there will be likely > > > a problem with way how buffers queue is implemented > > > > Only power of 2 makes sense to me: I didn't consider those corner > cases but the driver could just round down to the next power of 2 and > warn about a misconfiguration of the IP core. +1 > I added the dynamic detection because the IP core default had changed > to 2 TX buffers and this broke some hard coded assumptions in the > driver in a rather obscure way that had me debugging for a bit... The mainline driver uses a hard coded default of 4 still... Can you provide that patch soonish? > > You can make use of more TX buffers, if you implement (fully > > hardware based) TX IRQ coalescing (== handle more than one TX > > complete interrupt at a time) like in the mcp251xfd driver, or BQL > > support (== send more than one TX CAN frame at a time). I've played > > a bit with BQL support on the mcp251xfd driver (which is attached by > > SPI), but with mixed results. Probably an issue with proper > > configuration. > > Reducing CAN IRQ load would be good. IRQ coalescing comes at the price of increased latency, but if you have a timeout in hardware you can configure the latencies precisely. > > > We need 2 * priv->ntxbufs range to distinguish empty and full > > > queue... But modulo is not nice either so I probably come with > > > some other solution in a longer term. In the long term, I want to > > > implement virtual queues to allow multiqueue to use dynamic Tx > > > priority of up to 8 the buffers... > > > > ACK, multiqueue TX support would be nice for things like the > > Earliest TX Time First scheduler (ETF). 1 TX queue for ETF, the > > other for bulk messages. > > Would be nice, I have multi-queue in the CAN layer I wrote for a > little RTOS (predates socketcan) and have used for a while. Out of interest: What are the use cases? How did you decide which queue to use? regards, 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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