Date:   Tue, 16 Jan 2018 10:37:04 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Yixun Lan <yixun.lan@...ogic.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        davem@...emloft.net, netdev@...r.kernel.org,
        ingrassia@...genesys.com
Cc:     linus.luessing@...3.blue, narmstrong@...libre.com,
        khilman@...libre.com, alexandre.torgue@...com,
        linux-amlogic@...ts.infradead.org, peppe.cavallaro@...com
Subject: Re: [PATCH net-next v5 0/4] dwmac-meson8b: clock fixes for Meson8b

On Tue, 2018-01-16 at 16:25 +0800, Yixun Lan wrote:
> 
> On 01/16/18 01:10, Martin Blumenstingl wrote:
> > Hi Dave,
> > 
> > this series is now successfully tested, thus we think it's ready to be
> > applied to your net-next tree.
> > 
> > Emiliano reported [0] that he couldn't get dwmac-meson8b to work on his
> > Odroid-C1. This is the (hopefully) final version of this series, which
> > was successfully tested.
> > 
> > Due to the fact that the public S805/S905/S912 datasheets all seem to
> > be outdated regarding the description of the PRG_ETH0 (also called
> > PRG_ETHERNET_ADDR0) register Linus Lüssing offered to help testing with
> > an oscilloscope and an Odroid-C1. I would like to say HUGE thanks to him
> > at this point as he spent hours figuring out the effects of the bits
> > that are (though to be) relevant to get Ethernet working on the
> > Odroid-C1.
> > We tested three scenarios, all based on version 3 of this series:
> > 1) MPLL2 at ~500MHz, m250_div set to 1, bit 10 enabled
> > this resulted in a clock rate twice as high as expected at the RGMII TX
> > clock pin (250MHz instead of 125MHz for Gbit connections and 50MHz
> > instead of 25MHz for 100Mbit/s connections). it did not change the
> > rate at the XTAL_IN pin of PHY (which stayed consistenly at 25MHz)
> > 2) MPLL2 at ~250MHz, m250_div set to 1, bit 10 disabled
> > the oscilloscope shows "no clock" for the RGMII TX clock pin at it's
> > highest resolution (and random rates at lower resolutions). XTAL_IN is
> > still at 25MHz
> > 3) MPLL2 at ~250MHz, m250_div set to 1, bit 10 enabled
> > this resulted in a 125MHz signal at the RGMII TX clock pin for Gbit
> > speeds and 25MHz for 100Mbit/s - both values are as expected. The rate
> > on the XTAL_IN pin was at 25MHz
> > -> boot-logs (with the PRG_ETH0 register value) and screenshots from the
> > readings of the oscilloscope can be found at:
> > https://metameute.de/~tux/linux/amlogic/odroidc1/ethernet/
> > 
> > Version 4 of this series is based on the results from Linus Lüssing's
> > help with the oscilloscope and Odroid-C1.
> > Unfortunately I don't have any Meson8b boards with RGMII PHY so I could
> > only partially test this. @Emiliano: Could you please give this version
> > a try and let me know about the results (preferably with a "Tested-by"
> > if it works)?
> > You obviously still need your two "ARM: dts: meson8b" patches which
> > - add the amlogic,meson8b-dwmac" compatible to meson8b.dtsi
> > - enable Ethernet on the Odroid-C1 (according to your last thest a TX
> >   delay of 4ns is required to make it work properly)
> > 
> > When testing on Meson8b this also needs a fix for the MPLL clock driver:
> > "clk: meson: mpll: use 64-bit maths in params_from_rate", see:
> > https://patchwork.kernel.org/patch/10131677/
> > 
> > I have tested this myself on a Khadas VIM (GXL SoC, internal RMII PHY)
> > and a Khadas VIM2 (GXM SoC, external RGMII PHY). Both are still working
> > fine (so let's hope that this also fixes your Meson8b issue :)).
> > 
> > changes since v4 at [4]:
> > - dropped "RFT" status since Jerome tested this series successfully!
> > - dropped PATCH #2 ("simplify generating the clock names"). I will
> >   improve the whole clock registration in a separate series. since that
> >   patch didn't really improve anything I dropped it for now
> > - added Jerome's Acked-/Reviewed-/Tested-by's - many thanks!
> > 
> > changes since v3 at [3]:
> > - renamed the function PATCH #1 from meson8b_init_rgmii_clk to
> >   meson8b_init_rgmii_tx_clk since we now know what the register bits
> >   mean
> > - rewrote PATCH #3 because bit 10 is a gate clock and it seems that
> >   there is an internal fixed divide-by-2 clock. see the patch
> >   description for a detailed explanation
> > - updated the description of PATCH #4 and #5 as the clock we're trying
> >   to fix is the "RGMII TX" clock (old version stated that this is the
> >   "RGMII clock" or "PHY reference clock"). also updated the numbers in
> >   the description now that we have the clock hierarchy right (at least
> >   we hope so)
> > 
> > changes since v2 at [2]:
> > - added PATCH #2 to make the following patch easier
> > - Emiliano reported that there's currently another bug in the
> >   dwmac-meson8b driver which prevents it from working with RGMII PHYs on
> >   Meson8b: bit 10 of the PRG_ETH0 register is configures a clock gate
> >   (instead of a divide by 5 or divide by 10 clock divider). This has not
> >   been visible on GXBB and later due to the input clock which always led
> >   to a selection of "divide by 10" (which is done internally in the IP
> >   block, but the bit actually means "enable RGMII clock output").
> >   PATCH #3 was added to address this issue.
> > - the commit message of PATCH #4 and #5 (formerly PATCH #2 and #3) were
> >   updated and the patch itself rebased because the m25_div clock was
> >   removed with the new PATCH #3 (so some of the statements were not
> >   valid anymore)
> > 
> > changes since v1 at [1]:
> > - changed the subject of the cover-letter to indicate that this is all
> >   about the RGMII clock
> > - added PATCH #1 which ensures that we don't unnecessarily change the
> >   parent clocks in RMII mode (and also makes the code easier to
> >   understand)
> > - changed subject of PATCH #2 (formerly PATCH #1) to state that this
> >   is about the RGMII clock
> > - added Jerome's Reviewed-by to PATCH #2 (formerly PATCH #1)
> > - replaced PATCH #3 (formerly PATCH #2) with one that sets
> >   CLK_SET_RATE_PARENT on the mux and thus re-configures the MPLL2 clock
> >   on Meson8b correctly
> > 
> > 
> > [0] http://lists.infradead.org/pipermail/linux-amlogic/2017-December/005596.html
> > [1] http://lists.infradead.org/pipermail/linux-amlogic/2017-December/005848.html
> > [2] http://lists.infradead.org/pipermail/linux-amlogic/2017-December/005861.html
> > [3] http://lists.infradead.org/pipermail/linux-amlogic/2017-December/005899.html
> > [4] http://lists.infradead.org/pipermail/linux-amlogic/2018-January/006125.html
> > 
> > Martin Blumenstingl (4):
> >   net: stmmac: dwmac-meson8b: only configure the clocks in RGMII mode
> >   net: stmmac: dwmac-meson8b: fix internal RGMII clock configuration
> >   net: stmmac: dwmac-meson8b: fix setting the RGMII TX clock on Meson8b
> >   net: stmmac: dwmac-meson8b: propagate rate changes to the parent clock
> > 
> >  .../net/ethernet/stmicro/stmmac/dwmac-meson8b.c    | 113 ++++++++++++---------
> >  1 file changed, 63 insertions(+), 50 deletions(-)
> > 
> 
> 
> Hi Martin
> 
>  I'm having problem with this series applied.
> I've tested on the A113D (AXG) platform, if this patch is applied, the
> driver will choose MPLL2 as clk source, and seems it doesn't work out
> with this clk (fail to get IP)
> 
> grep mpll2 /sys/kernel/debug/clk/clk_summary
>        mpll2                              1            1   249999449
>      0 0
> 

This is because the fixed pll is 1992000000 on the axg instead of 2Ghz.
As a consequence fdiv4 is 498000000.

CCF can reach something closer to 250Mhz with the mpll2.

The easy way to fix this would be to make the inputs of ethernet mux optional
and not provide the MPLL2 on the axg.

However, this raises a few question on the axg platform :
1) Why is the root pll 1992Mhz and not 2GHz ? seems a weird choice just for 4MHz
This 1992Mhz does not seems to help generate audio freqs anymore than 2GHz
would. I don't really get this choice. Could you help us understand Yixun ?

2) Why is ethernet not working with mpll2 on axg ? espcially since we have
proven the rate be correct on meson8 ... is there any change on this platform we
don't know about ?

Regards

Jerome

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