RE: [PATCH v2 02/13] dt-bindings: serial: renesas,em-uart: Document r9a09g011 bindings

From: Phil Edworthy <phil.edworthy@renesas.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	Biju Das <biju.das.jz@bp.renesas.com>
Subject: RE: [PATCH v2 02/13] dt-bindings: serial: renesas,em-uart: Document r9a09g011 bindings
Date: Fri, 22 Apr 2022 08:28:33 +0000	[thread overview]
Message-ID: <TYYPR01MB7086BD705F91E855F0D3FD45F5F79@TYYPR01MB7086.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <CAMuHMdWaiAZNWmU5itJWJy3fEMmR1hQc7QRWpe6mi3AYkSewgw@mail.gmail.com>

Hi Geert,

(updated Krzysztof's email)

On 20 April 2022 22:26 Geert Uytterhoeven wrote:
> On Wed, Mar 30, 2022 at 5:41 PM Phil Edworthy <phil.edworthy@renesas.com>
> wrote:
> > The Renesas RZ/V2M (r9a09g011) SoC uses a uart that is compatible with
> the
> > EMMA Mobile SoC.
> >
> > Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
> > Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
> > ---
> > v2: Fix dtbs_check by adding missing alternative binding
> 
> Thanks for your patch, which is now commit 7bb301812b628099
> ("dt-bindings: serial: renesas,em-uart: Document r9a09g011
> bindings") in tty/tty-next.
> 
> > --- a/Documentation/devicetree/bindings/serial/renesas,em-uart.yaml
> > +++ b/Documentation/devicetree/bindings/serial/renesas,em-uart.yaml
> > @@ -14,7 +14,14 @@ allOf:
> >
> >  properties:
> >    compatible:
> > -    const: renesas,em-uart
> > +    oneOf:
> > +      - items:
> > +          - enum:
> > +              - renesas,r9a09g011-uart    # RZ/V2M
> > +          - const: renesas,em-uart        # generic EMMA Mobile
> compatible UART
> > +
> > +      - items:
> > +          - const: renesas,em-uart        # generic EMMA Mobile
> compatible UART
> 
> The above looks good to me.
> 
> >
> >    reg:
> >      maxItems: 1
> 
> However, unlike EMEV2, RZ/V2M defines two clocks: pclk and sclk.
> Hence please update the clocks section to reflect that.
You are right that the uart has two clocks.

Note though that pclk is shared by both uarts. The HW manual says:
"ch. 1 is for use with the ISP support package, so do not
use registers related to this channel.". Due to this, section
48.5.2.50 Clock ON/OFF Control Register 15 (CPG_CLK_ON15) says
that bit 20, CLK4_ONWEN (enable for URT_PCLK) should be written
as 0.

I took this to mean that the URT_PCLK is enabled by the ISP firmware
and software must not touch it. I am not sure if the DT bindings
should document a clock that is specified as do not touch in the
HW manual. This is a bit of a grey area.

Thanks
Phil