Message-ID: <ac036ba2-c9ce-1fb4-89e3-9af499954907@st.com>
Date:	Thu, 9 Jun 2016 08:20:05 +0200
From:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:	Tien Hock Loh <thloh@...era.com>
CC:	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <thloh85@...il.com>, <cnphoon@...era.com>
Subject: Re: [PATCH v3 1/1] net: ethernet: Add TSE PCS support to
 dwmac-socfpga

Hello Tien Hock

On 6/9/2016 7:48 AM, Tien Hock Loh wrote:

[snip]

>>>  .../devicetree/bindings/net/socfpga-dwmac.txt      |   4 +
>>>  drivers/net/ethernet/stmicro/stmmac/Makefile       |   2 +-
>>>  .../net/ethernet/stmicro/stmmac/dwmac-socfpga.c    | 140 +++++++++--
>>>  drivers/net/ethernet/stmicro/stmmac/tse_pcs.c      | 261 +++++++++++++++++++++
>>>  drivers/net/ethernet/stmicro/stmmac/tse_pcs.h      |  36 +++
>>>  5 files changed, 419 insertions(+), 24 deletions(-)
>>>  create mode 100644 drivers/net/ethernet/stmicro/stmmac/tse_pcs.c
>>>  create mode 100644 drivers/net/ethernet/stmicro/stmmac/tse_pcs.h
>>
>> I just wonder if it could make sense to rename the
>> tse_pcs.[hc] files or creating a sub-directory for altera devel.
>> It seems that tse_pcs.[hc] are common files but this support
>> is for Altera.
>> Anyway, I let you decide and I also ask you to update the stmmac.txt
>> file.
>
> Yeah the PCS support for TSE is Altera. To avoid confusion, let's rename
> them, would altr_tse_pcs.[hc] be good? I don't think creating a
> sub-directory with only 2 files is necessary though.

ok for two files w/o sub-dir.

>
> I see that stmmac.txt is generic, and other vendor's PCS support
> documents their specific uses in their own *-dwmac.txt (eg.
> rockchip-dwmac.txt). Is this not the case?

yes you can use this name convention. I let you decide.

[snip]


>>> +
>>> +		index = of_property_match_string(np_sgmii_adapter, "reg-names",
>>> +						 "eth_tse_control_port");
>>
>> reg-names looks to be specific and mandatory, IMO they should be
>> documented in the binding.
>
> That's the binding for the adapter (the phandle to the sgmii adapter),
> not the stmac binding itself. Do you mean I should document the sgmii
> adapter as well?

no I just meant for the adapter binding, I had understood that
eth_tse_control_port and gmii_to_sgmii_adapter_avalon_slave
were not documented and these seem to be mandatory.

[snip]

>>> +
>>> +static void auto_nego_timer_callback(unsigned long data)
>>> +{
>>> +	u16 val = 0;
>>> +	u16 speed = 0;
>>> +	u16 duplex = 0;
>>> +
>>> +	struct tse_pcs *pcs = (struct tse_pcs *)data;
>>> +	void __iomem *tse_pcs_base = pcs->tse_pcs_base;
>>> +	void __iomem *sgmii_adapter_base = pcs->sgmii_adapter_base;
>>> +
>>> +	val = readw(tse_pcs_base + TSE_PCS_STATUS_REG);
>>> +	val &=  TSE_PCS_STATUS_AN_COMPLETED_MASK;

[snip]

>>
>> ANE is completed but speed or duplex is NOK. Any failure to signalling?
>> I see that you then enable the adpter in any case.
>>
>> Maybe we could try to restart ANE again or force it (reducing the speed)
>> I wonder what happens if, for some reason, there is some hw problem. In
>> that case the timer is always running signalling an invalid Parter
>> speed. Anyway, this is jus a question... I expect that this error will
>> always point us to a problem to debug further (if occurs).
>
> Let me look at how we can handle the case. Perhaps we could do a restart
> and register the timer again. I'm just worried it will go into an
> infinite timer registering hogging up the kernel if the hardware really
> fails. Maybe I can do a n-time retry here. Looking into this. Let me
> know if you have any opinions on this.
>
> I haven't been able to check for this behaviour though, negative testing
> on this code isn't too easy to simulate.

yes and I expect this can occur on hw / conf problems. Take a look at
how the Physical Abstraction Layer manages this.
Indeed, we can try to restart ANE for a while and then just report the
failure (dev_err). Or we can try to fix other speed or duplex. But not
sure this is a good solution. We just mask a problem.

[snip]

>>> +
>>> +		setup_timer(&pcs->an_timer,
>>> +			    auto_nego_timer_callback,
>>> +			    (unsigned long)pcs);
>>> +		mod_timer(&pcs->an_timer, jiffies +
>>> +			  msecs_to_jiffies(AUTONEGO_TIMER));
>>> +	} else if (phy_dev->autoneg == AUTONEG_DISABLE) {
>>> +		val = readw(tse_pcs_base + TSE_PCS_CONTROL_REG);
>>> +		val &= ~TSE_PCS_CONTROL_AN_EN_MASK;
>>> +		writew(val, tse_pcs_base + TSE_PCS_CONTROL_REG);
>>> +
>>> +		val = readw(tse_pcs_base + TSE_PCS_IF_MODE_REG);
>>> +		val &= ~TSE_PCS_USE_SGMII_AN_MASK;
>>> +		writew(val, tse_pcs_base + TSE_PCS_IF_MODE_REG);
>>> +
>>> +		val = readw(tse_pcs_base + TSE_PCS_IF_MODE_REG);
>>> +		val &= ~TSE_PCS_SGMII_SPEED_MASK;
>>> +
>>> +		switch (speed) {
>>> +		case 1000:
>>> +			val |= TSE_PCS_SGMII_SPEED_1000;
>>> +			break;
>>> +		case 100:
>>> +			val |= TSE_PCS_SGMII_SPEED_100;
>>> +			break;
>>> +		case 10:
>>> +			val |= TSE_PCS_SGMII_SPEED_10;
>>> +			break;
>>> +		default:
>>> +			return;
>>> +		}
>>> +		writew(val, tse_pcs_base + TSE_PCS_IF_MODE_REG);
>>> +
>>> +		tse_pcs_reset(tse_pcs_base, pcs);
>>> +
>>> +		setup_timer(&pcs->link_timer,
>>> +			    pcs_link_timer_callback,
>>> +					(unsigned long)pcs);
>>> +		mod_timer(&pcs->link_timer, jiffies +
>>> +			  msecs_to_jiffies(LINK_TIMER));
>>
>> I wonder if we can have just one timer to manage ANE and LINK.
>>
>
> That would increase the complexity of the code because we would need to
> check the callback type on when the callback is triggered and call the
> correct function.

hmm, in that case, you have two timers and no lock protection:
I suspect there could be some hidden problem. The link goes down
and a timer polls this then another one try to restart ANE and
both timers read the TSE_PCS_STATUS_REG.
IMO, a timer is enough and you could keep the code to manage ANE and
LINK in two different functions. Pls take a look at if this is feasible.

Peppe

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