Hi Detlev, On Fri, 27 May 2011 17:26:24 +0200 Detlev Zundel <d...@denx.de> wrote: ... > > PCI cards might need some time after reset to respond. > > On some boards (mpc5200 or mpc8260 based) the PCI bus reset is > > deasserted at pci_board_init() time, so we can not use available > > "pcidelay" option for waiting before pci bus scan here. Add an option > > to delay bus scan by setting "pci_scan_delay" environment variable. > > Hm, I'm not sure I understand the situation, so please correct me. We > have a "pcidelay" variable, which is used to wait before > pci_board_init() (I'm not counting the semantically different usage in > the esd boards). This does not fit your need, so you define > pci_scan_delay which is used _after_ pci_init_board(), correct?
yes, this is correct. > If this is correct, then why don't you keep your new delay also in the > pci_init() function so that the delays are easily visible on code > inspection? But wait, if this is only needed for this very board, then > why don't we put the delay into digsys pci_init_board? Actually I think > this is the best way, as on this board we always need the delay as PCI > is not hotplug. The reason for not keeping new delay in pci_init() is: pci_init_board() starts scanning the bus (calls pci_hose_scan()), so when pci_init_board() returns, it is too late, the scanning is already completed. digsy's pci_init_board() just calls pci_mpc5xxx_init(), when the latter returns, the scanning is completed, too. PCI reset is de-asserted in pci_mpc5xxx_init(), so I thought about putting the delay there, but similar situation is also on mpc8260 based boards, pci_mpc8250_init() de-asserts PCI reset and waits on some boards (on MPC8266ADS 1 sec). So the problem is not only digsy specific. The needed time after reset before config cycles could be up to 1 sec, depending on the card. The pci spec 2.2 allows this. I think that it would be good to run arch specific pci init not from the pci_board_init(), but from pci_init(). Then we can add delay code in the board specific way. This would reduce the code duplication, too. Currently we have the same pci_init_board() for many 5200 boards, except for mvbc_p and mvsmr boards. > Apart from that, having two variables "pcidelay" and "pci_scan_delay" we > would need good documentation to explain their usage - the names do not > help (me) much ;) Sure. If there is an agreement to solve the problem as proposed in the patch, I'll add the documentation in the next patch version. Maybe someone have a better idea, lets wait a bit for other comments. Actually I don't like the name of the variable, it is somehow misleading. Any better name? Thanks, Anatolij _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
