Hi Dragan, On Wed, Nov 13, 2024 at 12:25 AM Dragan Simic <dsimic@xxxxxxxxxxx> wrote: > > Hello Tamas, > > On 2024-11-12 22:04, Tamás Szűcs wrote: > > On Tue, Nov 12, 2024 at 4:07 PM Dragan Simic <dsimic@xxxxxxxxxxx> > > wrote: > >> Please correct me if I'm wrong, but isn't this UART supposed to be > >> used for the Bluetooth part of an SDIO WiFi + Bluetooth module, in > >> form of a non-standard M.2 module that Radxa sells? > > > > UART8 is supposed to be used for any radio module connected to the M2E > > connector. > > It will typically be responsible for Bluetooth or BLE but it could be > > 802.15.4 or whatever. In any case, all wanting to use it will need the > > uart8 node enabled. > > I see, but I'm still guessing what's the actual use of enabling the > UART8 when it will remain pretty much useless without the additional > DT configuration, such as in the WiFi+Bluetooth DT overlay that Jonas > sent a bit earlier? The actual use is device enablement. > > I think that the UART8 should be enabled together with something that > actually makes use of it, which in this case unfortunately cannot be > automatically detected and configured, so it belongs to a DT overlay. > I'll get back to this in my next response. I agree, bluetooth blocks dedicated to specific modules should belong to DT overlays. > > >> With that in mind, I see very little sense in just enabling the UART, > >> without defining the entire Bluetooth interface, which AFAIK produces > > > > Defining a bluetooth node would hardwire idiosyncrasies of a given > > radio module's Bluetooth core. Sure you could add a sleep clock, all > > kind of sideband signals for wakeups, reset, power down, etc. But hey, > > some will use them, some won't. I think it's undesirable and > > unnecessary. You can hciattach from here and most will work just like > > that. Tighter integration or anything special, module specific on top > > should be handled individially, on a case-by-case basis. This is a dev > > board after all. I say trick of all trades. > > > >> nasty looking error messages in the kernel log when there's actually > >> nothing connected to the UART. > > > > My dmesg is clean as a whistle > > root@rock-3b:~# dmesg | grep -E 'fe6c0000|ttyS0' > > [ 0.344818] fe6c0000.serial: ttyS0 at MMIO 0xfe6c0000 (irq = 26, > > base_baud = 1500000) is a 16550A > > What kind of nasty errors do you recall? > > Those would be the kernel error messages produced with the Bluetooth > DT configuration in place, but with no SDIO module installed. These are the kernel messages related to UART8 with the uart8 DT node enabled and an SDIO module installed.
