The primecell device tree binding (from which the pl011 binding is derived from) states that the apb_pclk clock input should be listed first for all primecell devices. The amba-pl011 driver requires the uartclk clock input to enable the uart and calculate the correct uart baud rate, but the way it currently grabs the clock means that it always gets the first clock (which should be apb_pclk). As the AMBA bus code grabs apb_pclk by name, some existing dts provide uartclk then apb_pclk by name to work around this, in violation of both the primecell binding and the pl011 binding. Some dtbs only provide apb_pclk, which is evidently at a similar enough frequency to uartclk on those platforms to allow the driver to function. This patch attempts to fix the mess my having the amba-pl011 driver first attempt to get uartclk by name. If this fails, it falls back to the old behaviour of simply acquiring the first clock. This is compatible with any old dtb, whether it lists uartclk by name or not, and allows the driver to support dtbs which do not violate either binding. Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Rob Herring <robh+dt@xxxxxxxxxx> Cc: Pawel Moll <pawel.moll@xxxxxxx> --- drivers/tty/serial/amba-pl011.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index d58783d..067952a 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -2123,7 +2123,14 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) goto out; } - uap->clk = devm_clk_get(&dev->dev, NULL); + /* + * For compatibility with old DTBs and platform data, fall back to the + * first clock if there's not an explicitly named "uartclk" entry. + */ + uap->clk = devm_clk_get(&dev->dev, "uartclk"); + if (IS_ERR(uap->clk)) + uap->clk = devm_clk_get(&dev->dev, NULL); + if (IS_ERR(uap->clk)) { ret = PTR_ERR(uap->clk); goto out; -- 1.8.1.1 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html