On 9/29/19 11:49 AM, Thomas.Kopp@xxxxxxxxxxxxx wrote: > When testing the driver and using up/down multiple times on the CAN > interface I encountered errors with the TEF setup. I noticed that a > device reset (spi command) is only performed when loading the module > (in _mcp25xxfd_clock_probe during the initial clock setup.) > Is there a preference whether or not using up on the interface should > bring the device into a default state or is this only expected when > loading the module? I usually get all resources (clocks, regulators, ...), calculate all internal stuff during probe. Do a basic check, if the device is available, i.e. read a status register..., but not configure the device. Then I do a complete re-initialization of the chip during .ndo_open. > Are there any limits to how long up can/should take? How long does it take? :) > If a default state is desired after using up, I see two options to do this: Yes, better if a ifdown; ifup fixes a strange problem, than a rmmod; modprobe. > 1) Perform the reset procedure the same way it is done during loading > of the module including setting up the clock again. > 2) Bring all Registers to their default state "manually" and preserve > whatever clock was configured initially. I'd prefer 1), as _all_ registers should be in the default state (unless they are unaffected by the chip reset). > If 1) is used, stop can be simplified to perform a reset as well, no By "stop" you mean the .ndo_stop callback? Better not do a softreset, but shut down the device properly (manually). > need to care about resetting fifos etc. This is likely more time > consuming though. Doing it this way is time consuming because we need > to do the OSC setup again every time. > > 2) will usually be faster (assuming decent SPI speeds). The downside > is, that it's heavy on the SPI and we need to have default values for > all the registers for each supported device. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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