Andy Shevchenko <andriy.shevche...@linux.intel.com> writes: > On Fri, Apr 26, 2019 at 06:54:05PM +0200, Esben Haabendal wrote: >> Andy Shevchenko <andriy.shevche...@linux.intel.com> writes: >> > On Fri, Apr 26, 2019 at 10:40:37AM +0200, Esben Haabendal wrote: >> >> With serial8250_register_8250_port() forcing UPF_BOOT_AUTOCONF bit on, it >> >> is not possible to register a port without having >> >> serial8250_request_std_resource() called. >> >> >> >> For adding a 8250 port to an MFD device, this is problematic, as the >> >> request_mem_region() call will fail, as the MFD device (and rightly so) >> >> has requested the region. For this case, the 8250 port should accept >> >> having passed mapbase and membase, and just use that. >> > >> > You need to simple set port type and use UPF_FIXED_TYPE. >> > No need for this patch. >> >> 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. And I believe that is a valid thing to do. To workaround this, I first thought I could just avoid setting port->mapbase, causing serial8250_request_std_resource() to be a no-op. But this breaks with more than one UART port, as uart_match_port() will match the same line for all such UART ports, causing all but the last one to be removed. That said, the purpose of UPF_BOOT_AUTOCONF (for 8250 driver) is to request and map the register memory. So when that is already done by the parent MFD driver, I think it is silly to workaround problems caused by UPF_BOOT_AUTOCONF being force setted, when it really shouldn't. > Moreover, some drivers > are used as MFD counterparts with exactly same bits set. > >> I think it is unfortunate that UPF_BOOT_AUTOCONF is or'ed to flags like >> that, but changing that will surely break stuff. > > True.
