[U-Boot] [PATCH v2] serial: ns16550: Add register shift variable

[Lokesh Vutla]

On Tuesday 17 July 2018 12:32 PM, Felix Brack wrote:
> This patch adds a new Kconfig variable that allows setting
> the register offset shift value for the ns16550 driver to some
> other value then 0 if not defined by the DT. All credit for this
> patch goes to Lokesh Vutla as it was his idea.
> 
> The motivation for writing this patch originates in the
> effort of synchronizing U-Boot DT to Linux DT for am33xx SOCs.
> The current am33xx.dtsi file from U-Boot defines the <reg-shift>
> property for all UART nodes. The actual (4.18+) am33xx.dtsi
> file from Linux does not define <reg-shift> anymore. To prevent
> (probably difficult) changes in many .dts and .dtsi files once
> the synchronization is done, one can use this new variable. For
> the pdu001 board, for example, SYS_NS16550_REG_SHIFT is set
> to 2; no need to clutter U-Boot and board specific dts files
> with <reg-shift> properties.
> 
> Signed-off-by: Felix Brack <fb at ltec.ch>
> ---
> 
> Changes in v2:
> - clarify variable usage
> - set default value to 2 for AM33XX SoC
> 
>  drivers/serial/Kconfig   | 15 +++++++++++++++
>  drivers/serial/ns16550.c |  3 ++-
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> index 766e5ce..7eb3c6f 100644
> --- a/drivers/serial/Kconfig
> +++ b/drivers/serial/Kconfig
> @@ -530,6 +530,21 @@ config SYS_NS16550
>  	  be used. It can be a constant or a function to get clock, eg,
>  	  get_serial_clock().
>  
> +config SYS_NS16550_REG_SHIFT
> +	int "Amount of bits to shift register offsets left"
> +	default 2 if AM33XX

Can you make it default for ARCH_OMAP2PLUS?

Thanks and regards,
Lokesh


> +	default 0
> +	depends on SYS_NS16550
> +	help
> +	  Use this to specify the amount of bits to shift device register
> +	  offsets to the left. The resulting register offset is calculate as
> +	  follows: "reg offset" << SYS_NS16550_REG_SHIFT. If, for example,
> +	  the device register offsets are 0x00, 0x04, 0x08, 0x0C and so forth
> +	  than set this to 2.
> +	  In case of AM33XX SoC the default value is 2, 0 otherwise. Note
> +	  that a <reg-shift> property defined in a UART node of the device
> +	  tree will always take precedence.
> +
>  config INTEL_MID_SERIAL
>  	bool "Intel MID platform UART support"
>  	depends on DM_SERIAL && OF_CONTROL
> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> index 9c80090..9ff6dbe 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -442,7 +442,8 @@ int ns16550_serial_ofdata_to_platdata(struct udevice *dev)
>  #endif
>  
>  	plat->reg_offset = dev_read_u32_default(dev, "reg-offset", 0);
> -	plat->reg_shift = dev_read_u32_default(dev, "reg-shift", 0);
> +	plat->reg_shift = dev_read_u32_default(dev, "reg-shift",
> +					       CONFIG_SYS_NS16550_REG_SHIFT);
>  
>  	err = clk_get_by_index(dev, 0, &clk);
>  	if (!err) {
>