Hi Geert,
Thanks for your feedback.
On 2016-12-01 10:13:56 +0100, Geert Uytterhoeven wrote:
> Hi Niklas,
>
> On Mon, Nov 28, 2016 at 12:46 PM, Niklas Söderlund
> <niklas.soderlund+renesas@xxxxxxxxxxxx> wrote:
> > The EthernetAVB should not depend on the bootloader to setup correct
> > drive-strength values. Values for drive-strength where found by examine
>
> examining
>
> > the registers after the bootloader have configured the registers and
>
> has
>
Thanks.
> > successfully used the EthernetAVB.
> >
> > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> > ---
> > arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts | 28 ++++++++++++++++++++--
> > 1 file changed, 26 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts b/arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts
> > index b1eab68..7f49d19 100644
> > --- a/arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts
> > +++ b/arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts
> > @@ -225,8 +225,32 @@
> > };
> >
> > avb_pins: avb {
> > - groups = "avb_mdc";
> > - function = "avb";
> > + mux {
> > + groups = "avb_mdc", "avb_mii";
> > + function = "avb";
> > + };
> > +
> > + pins_mdc {
> > + groups = "avb_mdc";
> > + drive-strength = <24>;
> > + };
> > +
> > + pins_mii_tx {
> > + pins = "PIN_AVB_TX_CTL", "PIN_AVB_TXC", "PIN_AVB_TD0",
> > + "PIN_AVB_TD1", "PIN_AVB_TD2", "PIN_AVB_TD3";
> > + drive-strength = <12>;
> > + };
> > +
> > + pins_mii_rx {
> > + pins = "PIN_AVB_RX_CTL", "PIN_AVB_RXC", "PIN_AVB_RD0",
> > + "PIN_AVB_RD1", "PIN_AVB_RD2", "PIN_AVB_RD3";
> > + drive-strength = <24>;
> > + };
> > +
> > + pins_mii_clk {
> > + pins = "PIN_AVB_TXCREFCLK";
> > + drive-strength = <24>;
> > + };
> > };
> >
> > du_pins: du {
>
> What about AVB_PHY_INT and AVB_LINK?
> Or don't you need to specify their drive strengths, as they are input signals?
> Then what about pins_mii_rx, they're also input signals?
Wops, I was not aware of the u-boot repository you link bellow so was
looking at git://git.denx.de/u-boot-sh.git which also have some
salvator-x code, but nothing for EtherAVB.
My assumption hence was that it only used the pins from the avb_mdc
group and pins which could not be muxed, this is incorrect since u-boot
setup more pinmuxing. So there are more pin groups which should be
added to the mux section (at least). If I look at the u-boot code pins
missing in DT are:
- AVB_AVTP_CAPTURE_A
- AVB_AVTP_MATCH_A
- AVB_LINK
- AVB_PHY_INT
- AVB_MAGIC
I will add the pin groups which contain those pins to the mux section.
>
> BTW, the latest public U-Boot seems to configure just AVB_TX_CTL, AVB_TXC,
> and AVB_TXD[0-3] for 12 mA, cfr.
> https://github.com/renesas-rcar/u-boot/blob/v2015.04/rcar-3.4.0/board/renesas/salvator-x/salvator-x.c#L158
>
> According to the datasheet, the reset values of all signals are 15 mA on H3 ES1,
> and 24 mA on M3-W and H3 ES2.0.
This is good information, but how to make best use of it? Should I in DT
set the drive-strength for all pins or just the pins which diverge from
the reset default values? I think it's best to set them for all pins
since we should not depend on the bootloader, do you agree?
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> 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
--
Regards,
Niklas Söderlund
