[U-Boot] [PATCH v4 01/11] serial: ns16550: Support clocks via phandle

[Michal Simek]

On 1.8.2016 12:06, Paul Burton wrote:
> Previously ns16550 compatible UARTs probed via device tree have needed
> their device tree nodes to contain a clock-frequency property. An
> alternative to this commonly used with Linux is to reference a clock via
> a phandle. This patch allows U-Boot to support that, retrieving the
> clock frequency by probing the appropriate clock device.
> 
> For example, a system might choose to provide the UART base clock as a
> reference to a clock common to multiple devices:
> 
>   sys_clk: clock {
>     compatible = "fixed-clock";
>     #clock-cells = <0>;
>     clock-frequency = <10000000>;
>   };
> 
>   uart0: uart at 10000000 {
>     compatible = "ns16550a";
>     reg = <0x10000000 0x1000>;
>     clocks = <&sys_clk>;
>   };
> 
>   uart1: uart at 10000000 {
>     compatible = "ns16550a";
>     reg = <0x10001000 0x1000>;
>     clocks = <&sys_clk>;
>   };
> 
> This removes the need for the frequency information to be duplicated in
> multiple nodes and allows the device tree to be more descriptive of the
> system.
> 
> Signed-off-by: Paul Burton <paul.burton at imgtec.com>
> Reviewed-by: Simon Glass <sjg at chromium.org>
> 
> ---
> 
> Changes in v4: None
> Changes in v3: None
> Changes in v2:
> - Propogate non-ENODEV errors from clk_get_by_index
> 
>  drivers/serial/ns16550.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> index 88fca15..37da3ed 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -5,6 +5,7 @@
>   */
>  
>  #include <common.h>
> +#include <clk.h>
>  #include <dm.h>
>  #include <errno.h>
>  #include <fdtdec.h>
> @@ -352,6 +353,8 @@ int ns16550_serial_ofdata_to_platdata(struct udevice *dev)
>  {
>  	struct ns16550_platdata *plat = dev->platdata;
>  	fdt_addr_t addr;
> +	struct clk clk;
> +	int err;
>  
>  	/* try Processor Local Bus device first */
>  	addr = dev_get_addr(dev);
> @@ -397,9 +400,19 @@ int ns16550_serial_ofdata_to_platdata(struct udevice *dev)
>  				     "reg-offset", 0);
>  	plat->reg_shift = fdtdec_get_int(gd->fdt_blob, dev->of_offset,
>  					 "reg-shift", 0);
> -	plat->clock = fdtdec_get_int(gd->fdt_blob, dev->of_offset,
> -				     "clock-frequency",
> -				     CONFIG_SYS_NS16550_CLK);
> +
> +	err = clk_get_by_index(dev, 0, &clk);
> +	if (!err) {
> +		plat->clock = clk_get_rate(&clk);
> +	} else if (err != -ENODEV) {
> +		debug("ns16550 failed to get clock\n");
> +		return err;
> +	}
> +
> +	if (!plat->clock)
> +		plat->clock = fdtdec_get_int(gd->fdt_blob, dev->of_offset,
> +					     "clock-frequency",
> +					     CONFIG_SYS_NS16550_CLK);
>  	if (!plat->clock) {
>  		debug("ns16550 clock not defined\n");
>  		return -EINVAL;
> 


NACK. It is missing dependency on clk uclass which is not enabled by
default on Microblaze. Maybe also on others. You should add some ifs around.

Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP SoCs


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