On Fri, Apr 23, 2021 at 9:34 PM Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > > From: Jim Quinlan <jim2101024@xxxxxxxxx> > > Our SoC's have always had a NS16650A UART core and older SoC's would > have a compatible string of: 'compatible = ""ns16550a"' and use the > 8250_of driver. Our newer SoC's have added enhancements to the base > core to add support for DMA and accurate high speed baud rates and use > this newer 8250_bcm7271 driver. The Device Tree node for our enhanced > UARTs has a compatible string of: 'compatible = "brcm,bcm7271-uart", > "ns16550a"''. With both drivers running and the link order setup so > that the 8250_bcm7217 driver is initialized before the 8250_of driver, > we should bind the 8250_bcm7271 driver to the enhanced UART, or for > upstream kernels that don't have the 8250_bcm7271 driver, we bind to > the 8250_of driver. > > The problem is that when both the 8250_of and 8250_bcm7271 drivers > were running, occasionally the 8250_of driver would be bound to the > enhanced UART instead of the 8250_bcm7271 driver. This was happening > because we use SCMI based clocks which come up late in initialization > and cause probe DEFER's when the two drivers get their clocks. > > Occasionally the SCMI clock would become ready between the 8250_bcm7271 > probe and the 8250_of probe and the 8250_of driver would be bound. To > fix this we decided to config only our 8250_bcm7271 driver and added > "ns16665a0" to the compatible string so the driver would work on our > older system. > > This commit has of_platform_serial_probe() check specifically for the > "brcm,bcm7271-uart" and whether its companion driver is enabled. If it > is the case, and the clock provider is not ready, we want to make sure > that when the 8250_bcm7271.c driver returns EPROBE_DEFER, we are not > getting the UART registered via 8250_of.c. Thanks! Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> > Signed-off-by: Jim Quinlan <jim2101024@xxxxxxxxx> > Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx> > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx> > --- > drivers/tty/serial/8250/8250_of.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c > index 0b077b45d6a9..bce28729dd7b 100644 > --- a/drivers/tty/serial/8250/8250_of.c > +++ b/drivers/tty/serial/8250/8250_of.c > @@ -192,6 +192,10 @@ static int of_platform_serial_probe(struct platform_device *ofdev) > u32 tx_threshold; > int ret; > > + if (IS_ENABLED(CONFIG_SERIAL_8250_BCM7271) && > + of_device_is_compatible(ofdev->dev.of_node, "brcm,bcm7271-uart")) > + return -ENODEV; > + > port_type = (unsigned long)of_device_get_match_data(&ofdev->dev); > if (port_type == PORT_UNKNOWN) > return -EINVAL; > -- > 2.25.1 > -- With Best Regards, Andy Shevchenko
