[PATCH 10/16] serial: sh: Add RZ/G2L SCIF support

[Marek Vasut]

On 9/20/23 14:42, Paul Barker wrote:
> Extend the existing driver to support the SCIF serial ports on the
> Renesas RZ/G2L (R9A07G044) SoC. This also requires us to ensure that the
> relevant reset signal is de-asserted before we try to talk to the SCIF
> module.
> 
> Signed-off-by: Paul Barker <paul.barker.ct at bp.renesas.com>
> Reviewed-by: Biju Das <biju.das.jz at bp.renesas.com>
> Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj at bp.renesas.com>
> ---
>   arch/arm/mach-rmobile/Kconfig |  1 +
>   drivers/serial/serial_sh.c    | 32 ++++++++++++++++++++++++++++++--
>   drivers/serial/serial_sh.h    | 19 ++++++++++++++++++-
>   3 files changed, 49 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-rmobile/Kconfig b/arch/arm/mach-rmobile/Kconfig
> index 973e84fcf7ba..0ab22356aee5 100644
> --- a/arch/arm/mach-rmobile/Kconfig
> +++ b/arch/arm/mach-rmobile/Kconfig
> @@ -77,6 +77,7 @@ config RZG2L
>   	imply RENESAS_SDHI
>   	imply CLK_RZG2L
>   	imply PINCTRL_RZG2L
> +	imply SCIF_CONSOLE
>   	help
>   	  Enable support for the Renesas RZ/G2L family of SoCs, including the
>   	  the RZ/G2L itself (based on the R9A07G044 SoC).
> diff --git a/drivers/serial/serial_sh.c b/drivers/serial/serial_sh.c
> index 5e543dbf3d58..a2e9a57137a6 100644
> --- a/drivers/serial/serial_sh.c
> +++ b/drivers/serial/serial_sh.c
> @@ -17,6 +17,8 @@
>   #include <linux/compiler.h>
>   #include <dm/platform_data/serial_sh.h>
>   #include <linux/delay.h>
> +#include <dm/device_compat.h>
> +#include <reset.h>
>   #include "serial_sh.h"
>   
>   DECLARE_GLOBAL_DATA_PTR;
> @@ -79,8 +81,16 @@ sh_serial_setbrg_generic(struct uart_port *port, int clk, int baudrate)
>   
>   static void handle_error(struct uart_port *port)
>   {
> -	sci_in(port, SCxSR);
> -	sci_out(port, SCxSR, SCxSR_ERROR_CLEAR(port));
> +	/* The RZ/G2L datasheet says that error conditions are cleared by
> +	 * resetting the error bits in the FSR register to zero.

Can you be more specific here ?

It doesn't seem Linux sh-sci.c driver does anything special for G2L, so 
is this special case really needed ?

> +	 */
> +	if (IS_ENABLED(CONFIG_RZG2L)) {
> +		unsigned short status = sci_in(port, SCxSR);
> +		sci_out(port, SCxSR, status & ~SCIF_ERRORS);
> +	} else {
> +		sci_in(port, SCxSR);
> +		sci_out(port, SCxSR, SCxSR_ERROR_CLEAR(port));
> +	}
>   	sci_in(port, SCLSR);
>   	sci_out(port, SCLSR, 0x00);
>   }
> @@ -193,6 +203,23 @@ static int sh_serial_probe(struct udevice *dev)
>   	priv->type	= plat->type;
>   	priv->clk_mode	= plat->clk_mode;
>   
> +	if (IS_ENABLED(CONFIG_RZG2L)) {
> +		struct reset_ctl rst;
> +		int ret;
> +
> +		ret = reset_get_by_index(dev, 0, &rst);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to get reset line\n");
> +			return ret;
> +		}
> +
> +		ret = reset_deassert(&rst);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to de-assert reset line\n");
> +			return ret;
> +		}
> +	}

devm_reset_control_get_optional() or something should do here too , right ?

Note that R-Car does have SCIF reset too, so this can be generic code.