[RFC] serial: mxc: get the clock frequency from the used clock for the device
Sean Anderson
seanga2 at gmail.com
Thu Mar 17 15:38:45 CET 2022
Hi Heiko,
On 3/17/22 8:41 AM, Heiko Thiery wrote:
> With the clock driver enabled for the imx8mq, it was noticed that the
> frequency used to calculate the baud rate is always taken from the root
> clock of UART1. This can cause problems if UART1 is not used as console
> and the settings are different from UART1. The result is that the console
> output is garbage. To do this correctly the UART frequency is taken from
> the used device. For the implementations that don't have the igp clock
> frequency written or can't return it the old way is tried.
>
> Signed-off-by: Heiko Thiery <heiko.thiery at gmail.com>
> ---
> drivers/serial/serial_mxc.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
> index e4970a169b..6fdb2b2397 100644
> --- a/drivers/serial/serial_mxc.c
> +++ b/drivers/serial/serial_mxc.c
> @@ -3,6 +3,7 @@
> * (c) 2007 Sascha Hauer <s.hauer at pengutronix.de>
> */
>
> +#include <clk.h>
> #include <common.h>
> #include <dm.h>
> #include <errno.h>
> @@ -266,9 +267,19 @@ __weak struct serial_device *default_serial_console(void)
> int mxc_serial_setbrg(struct udevice *dev, int baudrate)
> {
> struct mxc_serial_plat *plat = dev_get_plat(dev);
> - u32 clk = imx_get_uartclk();
> + u32 rate = 0;
> +
> + if (IS_ENABLED(CONFIG_CLK)) {
CONFIG_IS_ENABLED?
mx6ull at least does not have CONFIG_SPL_CLK enabled.
> + struct clk clk;
> + if(!clk_get_by_name(dev, "ipg", &clk))
> + rate = clk_get_rate(&clk);
> + }
> +
> + /* as fallback we try to get the clk rate that way */
> + if (rate == 0)
!rate || IS_ERR_VALUE(rate)
> + rate = imx_get_uartclk();
>
> - _mxc_serial_setbrg(plat->reg, clk, baudrate, plat->use_dte);
> + _mxc_serial_setbrg(plat->reg, rate, baudrate, plat->use_dte);
>
> return 0;
> }
>
--Sean
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