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Date: Tue, 25 Oct 2016 01:56:01 +0000
From: Andy Duan <fugang.duan@....com>
To: Manfred Schlaegl <manfred.schlaegl@...zinger.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] net: fec: hard phy reset on open
From: Manfred Schlaegl <manfred.schlaegl@...zinger.com> Sent: Monday, October 24, 2016 10:43 PM
> To: Andy Duan <fugang.duan@....com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] net: fec: hard phy reset on open
>
> On 2016-10-24 16:03, Andy Duan wrote:
> > From: manfred.schlaegl@....at <manfred.schlaegl@....at> Sent:
> Monday,
> > October 24, 2016 5:26 PM
> >> To: Andy Duan <fugang.duan@....com>
> >> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> >> Subject: [PATCH] net: fec: hard phy reset on open
> >>
> >> We have seen some problems with auto negotiation on i.MX6 using
> >> LAN8720, after interface down/up.
> >>
> >> In our configuration, the ptp clock is used externally as reference
> >> clock for the phy. Some phys (e.g. LAN8720) needs a stable clock
> >> while and after hard reset.
> >> Before this patch, the driver disabled the clock on close but did no
> >> hard reset on open, after enabling the clocks again.
> >>
> >> A solution that prevents disabling the clocks on close was
> >> considered, but discarded because of bad power saving behavior.
> >>
> >> This patch saves the reset dt properties on probe and does a reset on
> >> every open after clocks where enabled, to make sure the clock is
> >> stable while and after hard reset.
> >>
> >> Tested on i.MX6 and i.MX28, both using LAN8720.
> >>
> >> Signed-off-by: Manfred Schlaegl <manfred.schlaegl@...zinger.com>
> >> ---
>
> > This patch did hard reset to let phy stable.
>
> > Firstly, you should do reset before clock enable.
> I have to disagree here.
> The phy demands(datasheet + tests) a stable clock at the time of (hard-
> )reset and after this. Therefore the clock has to be enabled before the hard
> reset.
> (This is exactly the reason for the patch.)
>
> Generally: The sense of a reset is to defer the start of digital circuit until the
> environment (power, clocks, ...) has stabilized.
>
> Furthermore: Before this patch the hard reset was done in fec_probe. And
> here also after the clocks were enabled.
>
> Whats was your argument to do it the other way in this special case?
>
I check some different vendor phy, hard reset assert after clock stable.
But I still don't ensure all phys are this action.
> > Secondly, we suggest to do phy reset in phy driver, not MAC driver.
> I was not sure, if you meant a soft-, or hard-reset here.
>
> In case you are talking about soft reset:
> Yes, the phy drivers perform a soft reset. Sadly a soft reset is not sufficient in
> this case - The phy recovers only on a hard reset from lost clock. (datasheet +
> tests)
>
> In case you're talking about hard reset:
> Intuitively I would also think, that the (hard-)reset should be handled by the
> phy driver, but this is not reality in given implementations.
>
> Documentation/devicetree/bindings/net/fsl-fec.txt says
>
> - phy-reset-gpios : Should specify the gpio for phy reset
>
> It is explicitly talked about phy-reset here. And the (hard-)reset was handled
> by the fec driver also before this patch (once on probe).
>
I suggest to do phy hard reset in phy driver like:
drivers/net/phy/spi_ks8995.c:
and Uwe Kleine-König's patch "phy: add support for a reset-gpio specification" (I don't know why the patch is reverted now.)
Regards,
Andy
> >
> > Regards,
> > Andy
>
> Thanks for your feedback!
>
> Best regards,
> Manfred
>
>
>
> >
> >> drivers/net/ethernet/freescale/fec.h | 4 ++
> >> drivers/net/ethernet/freescale/fec_main.c | 77
> >> +++++++++++++++++-------
> >> -------
> >> 2 files changed, 47 insertions(+), 34 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/freescale/fec.h
> >> b/drivers/net/ethernet/freescale/fec.h
> >> index c865135..379e619 100644
> >> --- a/drivers/net/ethernet/freescale/fec.h
> >> +++ b/drivers/net/ethernet/freescale/fec.h
> >> @@ -498,6 +498,10 @@ struct fec_enet_private {
> >> struct clk *clk_enet_out;
> >> struct clk *clk_ptp;
> >>
> >> + int phy_reset;
> >> + bool phy_reset_active_high;
> >> + int phy_reset_msec;
> >> +
> >> bool ptp_clk_on;
> >> struct mutex ptp_clk_mutex;
> >> unsigned int num_tx_queues;
> >> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> >> b/drivers/net/ethernet/freescale/fec_main.c
> >> index 48a033e..8cc1ec5 100644
> >> --- a/drivers/net/ethernet/freescale/fec_main.c
> >> +++ b/drivers/net/ethernet/freescale/fec_main.c
> >> @@ -2802,6 +2802,22 @@ static int fec_enet_alloc_buffers(struct
> >> net_device *ndev)
> >> return 0;
> >> }
> >>
> >> +static void fec_reset_phy(struct fec_enet_private *fep) {
> >> + if (!gpio_is_valid(fep->phy_reset))
> >> + return;
> >> +
> >> + gpio_set_value_cansleep(fep->phy_reset, !!fep-
> >>> phy_reset_active_high);
> >> +
> >> + if (fep->phy_reset_msec > 20)
> >> + msleep(fep->phy_reset_msec);
> >> + else
> >> + usleep_range(fep->phy_reset_msec * 1000,
> >> + fep->phy_reset_msec * 1000 + 1000);
> >> +
> >> + gpio_set_value_cansleep(fep->phy_reset, !fep-
> >>> phy_reset_active_high);
> >> +}
> >> +
> >> static int
> >> fec_enet_open(struct net_device *ndev) { @@ -2817,6 +2833,8 @@
> >> fec_enet_open(struct net_device *ndev)
> >> if (ret)
> >> goto clk_enable;
> >>
> >> + fec_reset_phy(fep);
> >> +
> >> /* I should reset the ring buffers here, but I don't yet know
> >> * a simple way to do that.
> >> */
> >> @@ -3183,52 +3201,39 @@ static int fec_enet_init(struct net_device
> *ndev)
> >> return 0;
> >> }
> >>
> >> -#ifdef CONFIG_OF
> >> -static void fec_reset_phy(struct platform_device *pdev)
> >> +static int
> >> +fec_get_reset_phy(struct platform_device *pdev, int *msec, int
> >> *phy_reset,
> >> + bool *active_high)
> >> {
> >> - int err, phy_reset;
> >> - bool active_high = false;
> >> - int msec = 1;
> >> + int err;
> >> struct device_node *np = pdev->dev.of_node;
> >>
> >> - if (!np)
> >> - return;
> >> + if (!np || !of_device_is_available(np))
> >> + return 0;
> >>
> >> - of_property_read_u32(np, "phy-reset-duration", &msec);
> >> + of_property_read_u32(np, "phy-reset-duration", msec);
> >> /* A sane reset duration should not be longer than 1s */
> >> - if (msec > 1000)
> >> - msec = 1;
> >> + if (*msec > 1000)
> >> + *msec = 1;
> >>
> >> - phy_reset = of_get_named_gpio(np, "phy-reset-gpios", 0);
> >> - if (!gpio_is_valid(phy_reset))
> >> - return;
> >> + *phy_reset = of_get_named_gpio(np, "phy-reset-gpios", 0);
> >> + if (!gpio_is_valid(*phy_reset))
> >> + return 0;
> >>
> >> - active_high = of_property_read_bool(np, "phy-reset-active-high");
> >> + *active_high = of_property_read_bool(np, "phy-reset-active-high");
> >>
> >> - err = devm_gpio_request_one(&pdev->dev, phy_reset,
> >> - active_high ? GPIOF_OUT_INIT_HIGH :
> >> GPIOF_OUT_INIT_LOW,
> >> - "phy-reset");
> >> + err = devm_gpio_request_one(&pdev->dev, *phy_reset,
> >> + *active_high ?
> >> + GPIOF_OUT_INIT_HIGH :
> >> + GPIOF_OUT_INIT_LOW,
> >> + "phy-reset");
> >> if (err) {
> >> dev_err(&pdev->dev, "failed to get phy-reset-gpios: %d\n",
> err);
> >> - return;
> >> + return err;
> >> }
> >>
> >> - if (msec > 20)
> >> - msleep(msec);
> >> - else
> >> - usleep_range(msec * 1000, msec * 1000 + 1000);
> >> -
> >> - gpio_set_value_cansleep(phy_reset, !active_high);
> >> -}
> >> -#else /* CONFIG_OF */
> >> -static void fec_reset_phy(struct platform_device *pdev) -{
> >> - /*
> >> - * In case of platform probe, the reset has been done
> >> - * by machine code.
> >> - */
> >> + return 0;
> >> }
> >> -#endif /* CONFIG_OF */
> >>
> >> static void
> >> fec_enet_get_queue_num(struct platform_device *pdev, int *num_tx,
> >> int
> >> *num_rx) @@ -3409,7 +3414,10 @@ fec_probe(struct platform_device
> >> *pdev)
> >> pm_runtime_set_active(&pdev->dev);
> >> pm_runtime_enable(&pdev->dev);
> >>
> >> - fec_reset_phy(pdev);
> >> + ret = fec_get_reset_phy(pdev, &fep->phy_reset_msec, &fep-
> >>> phy_reset,
> >> + &fep->phy_reset_active_high);
> >> + if (ret)
> >> + goto failed_reset;
> >>
> >> if (fep->bufdesc_ex)
> >> fec_ptp_init(pdev);
> >> @@ -3467,6 +3475,7 @@ fec_probe(struct platform_device *pdev)
> >> failed_mii_init:
> >> failed_irq:
> >> failed_init:
> >> +failed_reset:
> >> fec_ptp_stop(pdev);
> >> if (fep->reg_phy)
> >> regulator_disable(fep->reg_phy);
> >> --
> >> 2.1.4
>
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