linux-kernel - Re: [PATCH v3 4/4] serial: sh-sci: Add support for RZ/V2H(P) SoC

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Date: Tue, 19 Mar 2024 09:21:08 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Magnus Damm <magnus.damm@...il.com>, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-serial@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v3 4/4] serial: sh-sci: Add support for RZ/V2H(P) SoC

Hi Prabhakar,

On Mon, Mar 18, 2024 at 6:22 PM Prabhakar <prabhakar.csengg@...il.com> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Add serial support for RZ/V2H(P) SoC with earlycon.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> v2 - > v3
> - new patch

Thanks for your patch!

> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -290,7 +290,7 @@ static const struct sci_port_params sci_port_params[SCIx_NR_REGTYPES] = {
>         },
>
>         /*
> -        * The "SCIFA" that is in RZ/A2, RZ/G2L and RZ/T.
> +        * The "SCIFA" that is in RZ/A2, RZ/G2L, RZ/T and RZ/V2H.
>          * It looks like a normal SCIF with FIFO data, but with a
>          * compressed address space. Also, the break out of interrupts
>          * are different: ERI/BRI, RXI, TXI, TEI, DRI.

and RZ/V2H has more interrupts than RZ/A1, RZ/G2L and RZ/T...

In addition, RZ/V2H does not support synchronous mode (does not matter
for the driver) and modem control signals.

Currently, sci_init_pins() does write ones to the SCPTR bits that are
reserved and marked as "write zero" on RZ/V2H. I am not sure how bad
that is.  You could avoid that by adding a check for .hasrtscts, but
that may have impact on other SoCs/boards, where currently e.g. RTS#
is always programmed for output and active low...

So if you really need to avoid writing to these bits, the only safe
way may be to add a new SCIF type.  But perhaps I'm over-cautious? ;-)

> @@ -3224,6 +3224,10 @@ static const struct of_device_id of_sci_match[] __maybe_unused = {
>                 .compatible = "renesas,scif-r9a07g044",
>                 .data = SCI_OF_DATA(PORT_SCIF, SCIx_RZ_SCIFA_REGTYPE),
>         },
> +       {
> +               .compatible = "renesas,scif-r9a09g057",
> +               .data = SCI_OF_DATA(PORT_SCIF, SCIx_RZ_SCIFA_REGTYPE),
> +       },
>         /* Family-specific types */
>         {
>                 .compatible = "renesas,rcar-gen1-scif",
> @@ -3554,6 +3558,7 @@ OF_EARLYCON_DECLARE(sci, "renesas,sci", sci_early_console_setup);
>  OF_EARLYCON_DECLARE(scif, "renesas,scif", scif_early_console_setup);
>  OF_EARLYCON_DECLARE(scif, "renesas,scif-r7s9210", rzscifa_early_console_setup);
>  OF_EARLYCON_DECLARE(scif, "renesas,scif-r9a07g044", rzscifa_early_console_setup);
> +OF_EARLYCON_DECLARE(scif, "renesas,scif-r9a09g057", rzscifa_early_console_setup);
>  OF_EARLYCON_DECLARE(scifa, "renesas,scifa", scifa_early_console_setup);
>  OF_EARLYCON_DECLARE(scifb, "renesas,scifb", scifb_early_console_setup);
>  OF_EARLYCON_DECLARE(hscif, "renesas,hscif", hscif_early_console_setup);

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds