Hi Niklas,
On Thu, Dec 1, 2016 at 11:29 AM, Niklas Söderlund
<niklas.soderlund@xxxxxxxxxxxx> wrote:
> On 2016-12-01 10:13:56 +0100, Geert Uytterhoeven wrote:
>> On Mon, Nov 28, 2016 at 12:46 PM, Niklas Söderlund
>> > 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.
Note that AVB_AVTP_CAPTURE_A, AVB_AVTP_MATCH_A, and AVB_MAGIC are not
used on Salvator-X.
>> 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?
For input-only pins, drive strength should not matter at all, so I think you
should leave it out.
For other (used) pins, I think it should be specified.
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
