On Sun, Mar 17, 2024 at 10:41:23PM +0100, Hans de Goede wrote:
Commit e5d6bd25f93d ("serial: 8250_dw: Do not reclock if already at correct rate") breaks the dw UARTs on Intel Bay Trail (BYT) and Cherry Trail (CHT) SoCs.
Before this change the RTL8732BS Bluetooth HCI which is found connected over the dw UART on both BYT and CHT boards works properly:
Bluetooth: hci0: RTL: examining hci_ver=06 hci_rev=000b lmp_ver=06 lmp_subver=8723 Bluetooth: hci0: RTL: rom_version status=0 version=1 Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_fw.bin Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_config-OBDA8723.bin Bluetooth: hci0: RTL: cfg_sz 64, total sz 24508 Bluetooth: hci0: RTL: fw version 0x365d462e
where as after this change probing it fails:
Bluetooth: hci0: RTL: examining hci_ver=06 hci_rev=000b lmp_ver=06 lmp_subver=8723 Bluetooth: hci0: RTL: rom_version status=0 version=1 Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_fw.bin Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_config-OBDA8723.bin Bluetooth: hci0: RTL: cfg_sz 64, total sz 24508 Bluetooth: hci0: command 0xfc20 tx timeout Bluetooth: hci0: RTL: download fw command failed (-110)
Revert the changes to fix this regression.
Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
Note it is not entirely clear to me why this commit is causing this issue. Maybe probe() needs to explicitly set the clk rate which it just got (that feels like a clk driver issue) or maybe the issue is that unless setup before hand by firmware / the bootloader serial8250_update_uartclk() needs to be called at least once to setup things ? Note that probe() does not call serial8250_update_uartclk(), this is only called from the dw8250_clk_notifier_cb()
This requires more debugging which is why I'm proposing a straight revert to fix the regression ASAP and then this can be investigated further.
Yep. When I reviewed the original submission I was got puzzled with the CLK APIs. Now I might remember that ->set_rate() can't be called on prepared/enabled clocks and it's possible the same limitation is applied to ->round_rate().
I also tried to find documentation about the requirements for those APIs, but failed (maybe was not pursuing enough, dunno). If you happen to know the one, can you point on it?