[U-Boot] [PATCH 1/2] serial: add skipping init option

[Jun Nie]

Lukasz Majewski <lukma at denx.de> 于2019年3月27日周三 下午5:34写道：
>
> Hi Simon, Jun,
>
> > Hi Jun,
> >
> > On Fri, 22 Mar 2019 at 16:02, Jun Nie <jun.nie at linaro.org> wrote:
> > >
> > > Simon Glass <sjg at chromium.org> 于2019年3月22日周五 下午3:56写道：
> > > >
> > > > Hi Jun,
> > > >
> > > > On Fri, 22 Mar 2019 at 15:20, Jun Nie <jun.nie at linaro.org>
> > > > wrote:
> > > > >
> > > > > add skipping init option to avoid corrupt data in console
> > > > > if serial is already initilized when u-boot start its excution.
> > > > >
> > > > > Signed-off-by: Jun Nie <jun.nie at linaro.org>
> > > > > ---
> > > > >  drivers/serial/Kconfig | 6 ++++++
> > > > >  1 file changed, 6 insertions(+)
> > > >
> > > > Could we use a device-tree property for this? Some UARTs have a
> > > > 'skip-init' property.
> > > >
> > > > Regards,
> > > > Simon
> > >
> > > Hi Simon,
> > >
> > > It is a good suggestion. But device tree is board specific, while
> > > the config is boot flow specific. For ATF -> OPTEE -> U-BOOT case,
> > > initialization should be skipped. Without earlier initialization
> > > from firmware, U-boot should do it by itself. So I need find a
> > > solution that is defconfig specific, instead of device tree
> > > specific.
> >
> > So you want something that is flow-specific, I think. Your thinking is
> > that the defconfig specifies this. Is that because certain boards
> > require ATF/Optee?
> >
> > Should we consider having a way to tell U-Boot that it is running
> > from Optee?
> >
> > Could the UART driver detect that the UART is already inited?
>
> Isn't this issue similar to:
> http://patchwork.ozlabs.org/patch/820824/
>
> and
>
> http://patchwork.ozlabs.org/patch/865963/
>
My case is that console does not emit any log when OPTEE runs into u-boot.
I already root caused that there is a bug in uart clock handling.
UART1_CLK_ROOT
is hard coded in imx_get_uartclk() of arch/arm/mach-imx/mx7/clock.c
If the console serial is not UART1, 0 may be returned and console does not work.

But when I add an IMX_UART_PORT config option in Kconfig to dynamic configure
the CLK_ROOT ID as below, the expansion result is
UARTCONFIG_IMX_UART_PORT_CLK_ROOT instead of  UART1_CLK_ROOT.
It seems macro expansion happens before the inclusion of defconfig. Do you see
any better idea other than add the definition in
include/configs/pico-imx7d.h directly?

#define IMX_UART_CLK_ROOT     UART##CONFIG_IMX_UART_PORT##_CLK_ROOT

Current plan is to add below change so that platform can define
different clock root other
than UART1_CLK_ROOT.

+++ b/arch/arm/mach-imx/mx7/clock.c
@@ -51,9 +51,12 @@ static u32 get_ipg_clk(void)
        return get_ahb_clk() / 2;
 }

+#ifndef UART_CLK_ROOT
+#define UART_CLK_ROOT UART1_CLK_ROOT
+#endif
 u32 imx_get_uartclk(void)
 {
-       return get_root_clk(UART1_CLK_ROOT);
+       return get_root_clk(UART_CLK_ROOT);
 }

> >
> > Regards,
> > Simon
> > _______________________________________________
> > U-Boot mailing list
> > U-Boot at lists.denx.de
> > https://lists.denx.de/listinfo/u-boot
>
>
>
>
> Best regards,
>
> Lukasz Majewski
>
> --
>
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