On Thu, 9 Oct 2014, Steffen Trumtrar wrote: > On Thu, Oct 09, 2014 at 08:16:18AM -0500, Dinh Nguyen wrote: > > Hi Philipp, > > > > On 10/9/14, 4:03 AM, Philipp Zabel wrote: > > > Am Mittwoch, den 08.10.2014, 21:44 -0500 schrieb > > > dinguyen@xxxxxxxxxxxxxxxxxxxxx: > > >> From: Dinh Nguyen <dinguyen@xxxxxxxxxxxxxxxxxxxxx> > > >> > > >> There are certain drivers that are required to get loaded very early using > > >> arch_initcall. An example of such a driver is the SOCFPGA's FPGA bridge driver. > > >> This driver has to get loaded early because it needs to enable FPGA components > > >> that are connected to the bridge. > > >> > > >> This FPGA bridge driver will using the reset controller API to toggle it's > > >> reset bits, thus, it needs the reset driver to be loaded as early as possible > > >> in order for it to get used properly. > > > > > > Without knowing the details, this sounds like the wrong approach. Can't > > > the bridge driver return -EPROBE_DEFER until the reset controller is > > > available? > > > I don't think we can do deferred probing for arch_initcall. > > > > The bridge driver is also using arch_initcall, as it also needs to get > > loaded early for FPGA IPs to work, and so later driver loading will work > > for the FPGA IPs. > > > > For the bridge driver the same is true. I guess that there *might* be > IP cores where you need to be very early, but that shouldn't be the normal > case. If the driver can't get loaded properly, the right thing would be to > fix the driver. Some fpga ip drivers will need to be early (and will assume that the fpga was programmed by the bootloader). We want to support that case. > > I have developed a bridge driver, too (which only needs the devicetree binding > docu for a v1) and I have a driver+IP core that is directly connected to the > bridge. I don't need any messing around with the initcalls to work properly. > -EPROBE_DEFER works just fine. Is this based on the "proposed fpga bridge framework" that I posted? What we are trying to do is update that bridge driver to use the reset driver for submitting v2. Alan > > What I do need however is loading the FPGA very early of course, if it is not > done in the bootloader. > > Regards, > Steffen > > -- > Pengutronix e.K. | | > Industrial Linux Solutions | http://www.pengutronix.de/ | > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
