Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 19 Oct 2021 17:44:08 +0200 | Subject | Re: [PATCH] net: renesas: Fix rgmii-id delays |
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Hi Köry,
On Tue, Oct 19, 2021 at 5:35 PM Köry Maincent <kory.maincent@bootlin.com> wrote: > On Tue, 19 Oct 2021 17:13:52 +0200 > Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > > The ravb MAC is adding RX delay if RGMII_RXID is selected and TX delay > > > if RGMII_TXID but that behavior is wrong. > > > Indeed according to the ethernet.txt documentation the ravb configuration > > > should be inverted: > > > * "rgmii-rxid" (RGMII with internal RX delay provided by the PHY, the MAC > > > should not add an RX delay in this case) > > > * "rgmii-txid" (RGMII with internal TX delay provided by the PHY, the MAC > > > should not add an TX delay in this case) > > > > > > This patch inverts the behavior, i.e adds TX delay when RGMII_RXID is > > > selected and RX delay when RGMII_TXID is selected. > > > > > > Signed-off-by: Kory Maincent <kory.maincent@bootlin.com> > > > > Does this fix an actual problem for you? > > In fact, this fix a problem for an older 4.14 Kernel on my current project. > I wanted to push my fix in the mainline kernel also, but as you say below, now > this code is legacy. > Does it matter to fix legacy code?
I don't think so. If you're stuck on v4.14, you may want to backport commit a6f51f2efa742df0 ("ravb: Add support for explicit internal clock delay configuration"). However, you have to be careful, as it interacts with related changes to PHY drivers, as explained in that commit.
> > Note that in accordance with the comment above, the code section > > below is only present to support old DTBs. Contemporary DTBs rely > > on the now mandatory "rx-internal-delay-ps" and "tx-internal-delay-ps" > > properties instead. > > Hence changing this code has no effect on DTS files as supplied with > > the kernel, but may have ill effects on DTB files in the field, which > > rely on the current behavior. > > When people update the kernel version don't they update also the devicetree?
I hope they do ;-) But we do our best to preserve backwards-compatibility with old DTBS. If you change behavior of v4.14, it may actually introduce backwards-incompatibility we're not aware of, as the behavior you started to rely on never existed in mainline.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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
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