On Mon, Apr 29, 2019 at 9:27 AM Esben Haabendal <esben@xxxxxxxxxxxx> wrote: > Andy Shevchenko <andy.shevchenko@xxxxxxxxx> writes: > > On Sat, Apr 27, 2019 at 12:01 PM Esben Haabendal <esben@xxxxxxxxxxxx> wrote: > >> Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes: > >> > On Fri, Apr 26, 2019 at 06:54:05PM +0200, Esben Haabendal wrote: > >> >> Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes: > >> >> The reason for this patch is to be able to do exactly that (set port > >> >> type and UPF_FIXED_TYPE) without having UPF_BOOT_AUTOCONF added. > >> >> > >> >> In the current serial8250_register_8250_port() there is: > >> >> > >> >> uart->port.flags = up->port.flags | UPF_BOOT_AUTOCONF; > >> >> > >> >> So, even though I set UPF_FIXED_TYPE, I get > >> >> UPF_FIXED_TYPE|UPF_BOOT_AUTOCONF. > >> > > >> > Yes. > >> > > >> >> So I need this patch. > >> > > >> > Why? I don't see any problems to have these flags set. > >> > >> The problem with having UPF_BOOT_AUTOCONF is the call to > >> serial8250_request_std_resource(). It calls request_mem_region(), which > >> fails if the MFD driver already have requested the memory region for the > >> MFD device. > > > > If it's MFD, why it requested the region for its child? > > Isn't it a bug in MFD driver? > > It is a PCI driver, which calls pci_request_regions(). The PCI device > carries a lot of different functions, which uses small slices of the PCI > memory region(s). With the resources being a tree structure, I don't > think it is a bug when a parent driver requests the entire memory > region. If it's MFD driver, it's not its business to do something child-related on child behalf. In any case, Linux device resource model uses exclusive region slicing. If you do like above, you call for a problems. Btw, we have PCI MFD driver which enumerates 8250 (more precisely 8250_dw) w/o any issues. > It would be nice if child drivers requesting memory would pass the > parent memory resource. Maybe 8250 driver could be changed to accept a > struct resource pointer instead of a simple mapbase value, allowing to > setup the resource with parent pointing to the MFD memory resource. I don't see the problem in certain driver, I guess you are trying to workaround existin Linux device resource model. -- With Best Regards, Andy Shevchenko
