Hi Andrew, +CC Kishon On Thu, 7 Nov 2019 12:46:17 +0000 <andrew.murray@xxxxxxx> wrote: > On Thu, Nov 07, 2019 at 08:52:39PM +0900, Kunihiko Hayashi wrote: > > Hi Andrew, > > Thank you for your comments. > > > > On Thu, 7 Nov 2019 10:02:08 +0000 <andrew.murray@xxxxxxx> wrote: > > > > > On Thu, Nov 07, 2019 at 01:58:15PM +0900, Kunihiko Hayashi wrote: > > > > When PERST# is asserted once, EP configuration will be initialized. > > > > > > I don't quite understand this - does the EP/RC mode depend on how often > > > PERST# is toggled? > > > > I think of connecting this RC controller and EP based on `Linux PCI > > endpoint framework' in another machine. > > > > While this RC driver is probing, the EP driver might be also probing and > > configurating itself using configfs. If PERST# is toggled after the EP > > has done its configuration, this configuration will be lost. > > > > I expect that the EP configurates after RC has toggled PERST#, however, > > there is no way to synchronize both of them. > > > > OK I understand where you are coming from now. Please ensure the commit > message gives this rationale. I'll explain about that in the commit message next. > However, If I understand correctly, doesn't your solution only work some > of the time? What happens if you boot both machines at the same time, > and PERST# isn't asserted prior to the kernel booting? I think it contains an annoying problem. If PERST# isn't toggled prior to the kernel booting, PERST# remains asserted and the RC driver can't access PCI bus. As a result, this patch works and deasserts PERST# (and EP configuration will be lost). So boot sequence needs to include deasserting PERST#. > The only way you can ensure the EP is started after the RC is initialised > is to start the EP after the RC is initialised. Yes, it's the only soution for now. > I'm not sure what the solution is here, but it feels like this approach > only partially solves it. Surely relying on outside of the driver doesn't seem to be a complete solution. If there is the way that `Linux PCI endpoint framework' assumes, I'd like to follow it, however, I can't find the other way. Thank you, --- Best Regards, Kunihiko Hayashi
