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Date: Tue, 26 Dec 2023 16:40:21 +0530
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Subject: Re: [PATCH net-next v8 3/3] net: stmmac: Add driver support for
 DWMAC5 common safety IRQ
Content-Language: en-US
To: Serge Semin <fancer.lancer@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet
	<edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni
	<pabeni@redhat.com>, Vinod Koul <vkoul@kernel.org>,
        Bhupesh Sharma
	<bhupesh.sharma@linaro.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson
	<andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Rob Herring
	<robh+dt@kernel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu
	<joabreu@synopsys.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>, <netdev@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        Prasad Sodagudi
	<psodagud@quicinc.com>,
        Andrew Halaney <ahalaney@redhat.com>, Rob Herring
	<robh@kernel.org>,
        <kernel@quicinc.com>
References: <20231221073620.232619-1-quic_jsuraj@quicinc.com>
 <20231221073620.232619-4-quic_jsuraj@quicinc.com>
 <yromhtr73rwsr6hizr4tq37vfvyzfue7wzpmufqyscwspzffza@uhfcrn573acd>
 <aec2dc6a-ffa4-4753-a764-77dfe1af995a@quicinc.com>
 <xdcrwxh7e4t2zkgdcfwzjr2z4ouwgv3vr4drwvshadxmpwyqkd@j3kj3p2u7nd7>
From: Suraj Jaiswal <quic_jsuraj@quicinc.com>
In-Reply-To: <xdcrwxh7e4t2zkgdcfwzjr2z4ouwgv3vr4drwvshadxmpwyqkd@j3kj3p2u7nd7>
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Hi seren
let me check below on test setup once & get back

Thanks
Suraj

On 12/22/2023 8:05 PM, Serge Semin wrote:
> On Fri, Dec 22, 2023 at 02:13:49PM +0530, Suraj Jaiswal wrote:
>> HI Serge,
>> please find commnet inline.
>>
>> Thanks
>> Suraj
>>
>> On 12/21/2023 6:19 PM, Serge Semin wrote:
>>> Hi Suraj
>>>
>>> On Thu, Dec 21, 2023 at 01:06:20PM +0530, Suraj Jaiswal wrote:
>>>> Add support to listen HW safety IRQ like ECC(error
>>>> correction code), DPP(data path parity), FSM(finite state
>>>> machine) fault in common IRQ line.
>>>>
>>>> Signed-off-by: Suraj Jaiswal <quic_jsuraj@quicinc.com>
>>>
>>> Thanks for taking my notes into account. One more comment is further
>>> below.
>>>
>>>> ---
>>>>  drivers/net/ethernet/stmicro/stmmac/common.h  |  1 +
>>>>  drivers/net/ethernet/stmicro/stmmac/stmmac.h  |  3 ++
>>>>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 37 +++++++++++++++++++
>>>>  .../ethernet/stmicro/stmmac/stmmac_platform.c |  8 ++++
>>>>  4 files changed, 49 insertions(+)
>>>>
>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
>>>> index 721c1f8e892f..b9233b09b80f 100644
>>>> --- a/drivers/net/ethernet/stmicro/stmmac/common.h
>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/common.h
>>>> @@ -344,6 +344,7 @@ enum request_irq_err {
>>>>  	REQ_IRQ_ERR_ALL,
>>>>  	REQ_IRQ_ERR_TX,
>>>>  	REQ_IRQ_ERR_RX,
>>>> +	REQ_IRQ_ERR_SFTY,
>>>>  	REQ_IRQ_ERR_SFTY_UE,
>>>>  	REQ_IRQ_ERR_SFTY_CE,
>>>>  	REQ_IRQ_ERR_LPI,
>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>> index 9f89acf31050..ca3d93851bed 100644
>>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>>>> @@ -31,6 +31,7 @@ struct stmmac_resources {
>>>>  	int wol_irq;
>>>>  	int lpi_irq;
>>>>  	int irq;
>>>> +	int sfty_irq;
>>>>  	int sfty_ce_irq;
>>>>  	int sfty_ue_irq;
>>>>  	int rx_irq[MTL_MAX_RX_QUEUES];
>>>> @@ -297,6 +298,7 @@ struct stmmac_priv {
>>>>  	void __iomem *ptpaddr;
>>>>  	void __iomem *estaddr;
>>>>  	unsigned long active_vlans[BITS_TO_LONGS(VLAN_N_VID)];
>>>> +	int sfty_irq;
>>>>  	int sfty_ce_irq;
>>>>  	int sfty_ue_irq;
>>>>  	int rx_irq[MTL_MAX_RX_QUEUES];
>>>> @@ -305,6 +307,7 @@ struct stmmac_priv {
>>>>  	char int_name_mac[IFNAMSIZ + 9];
>>>>  	char int_name_wol[IFNAMSIZ + 9];
>>>>  	char int_name_lpi[IFNAMSIZ + 9];
>>>> +	char int_name_sfty[IFNAMSIZ + 10];
>>>>  	char int_name_sfty_ce[IFNAMSIZ + 10];
>>>>  	char int_name_sfty_ue[IFNAMSIZ + 10];
>>>>  	char int_name_rx_irq[MTL_MAX_TX_QUEUES][IFNAMSIZ + 14];
>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>> index 47de466e432c..7d4e827dfeab 100644
>>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>>> @@ -3592,6 +3592,10 @@ static void stmmac_free_irq(struct net_device *dev,
>>>>  		if (priv->wol_irq > 0 && priv->wol_irq != dev->irq)
>>>>  			free_irq(priv->wol_irq, dev);
>>>>  		fallthrough;
>>>> +	case REQ_IRQ_ERR_SFTY:
>>>> +		if (priv->sfty_irq > 0 && priv->sfty_irq != dev->irq)
>>>> +			free_irq(priv->sfty_irq, dev);
>>>> +		fallthrough;
>>>>  	case REQ_IRQ_ERR_WOL:
>>>>  		free_irq(dev->irq, dev);
>>>>  		fallthrough;
>>>> @@ -3661,6 +3665,23 @@ static int stmmac_request_irq_multi_msi(struct net_device *dev)
>>>>  		}
>>>>  	}
>>>>  
>>>> +	/* Request the common Safety Feature Correctible/Uncorrectible
>>>> +	 * Error line in case of another line is used
>>>> +	 */
>>>> +	if (priv->sfty_irq > 0 && priv->sfty_irq != dev->irq) {
>>>> +		int_name = priv->int_name_sfty;
>>>> +		sprintf(int_name, "%s:%s", dev->name, "safety");
>>>> +		ret = request_irq(priv->sfty_irq, stmmac_safety_interrupt,
>>>> +				  0, int_name, dev);
>>>> +		if (unlikely(ret < 0)) {
>>>> +			netdev_err(priv->dev,
>>>> +				   "%s: alloc sfty MSI %d (error: %d)\n",
>>>> +				   __func__, priv->sfty_irq, ret);
>>>> +			irq_err = REQ_IRQ_ERR_SFTY;
>>>> +			goto irq_error;
>>>> +		}
>>>> +	}
>>>> +
>>>>  	/* Request the Safety Feature Correctible Error line in
>>>>  	 * case of another line is used
>>>>  	 */
>>>> @@ -3798,6 +3819,21 @@ static int stmmac_request_irq_single(struct net_device *dev)
>>>>  		}
>>>>  	}
>>>>  
>>>> +	/* Request the common Safety Feature Correctible/Uncorrectible
>>>> +	 * Error line in case of another line is used
>>>> +	 */
>>>> +	if (priv->sfty_irq > 0 && priv->sfty_irq != dev->irq) {
>>>
>>>> +		ret = request_irq(priv->sfty_irq, stmmac_safety_interrupt,
>>>> +				  IRQF_SHARED, dev->name, dev);
>>>
>>> Just noticed yesterday that stmmac_safety_interrupt() is also called
>>> from the stmmac_interrupt() handler which is supposed to be registered
>>> on the generic "mac" IRQ. Won't it cause races around the CSRs
>>> (doubtfully but still worth to note) and the errors handling
>>> (stmmac_global_err()) in case if both IRQs are raised simultaneously?
>>> At the very least it looks suspicious and worth double-checking.
>>>
>>> I also found out that nobody seemed to care that the same handler is
>>> registered on MAC, WoL and LPI IRQ lines. Hmm, no race-related
>>> problems have been reported so far for the platforms with separate
>>> WoL/LPI IRQs. It's either a lucky coincident or the IRQs are always
>>> assigned to the same CPU or the IRQs handle is indeed free of races.
>>> In anyway it looks suspicious too. At the very least AFAICS the DMA
>>> IRQ-handler is indeed racy on the status CSR access. It isn't
>>> cleared-on-read, but write-one-to-clear. So the statistics might be
>>> calculated more than once for the same CSR state. There might be some
>>> other problems I failed to spot on the first glance.
>>>
>>> David, Eric, Jacub, Paolo, your opinion about the note above?
>>>
>>> -Serge(y)
>>>
> 
>> <Suraj> We are adding common IRQ similar to already present code for correcteable/uncorrecable https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c#L3592.
> 
> From that perspective your change in stmmac_request_irq_multi_msi() is
> correct, but stmmac_request_irq_single() is another story. The first
> one method implies assigning the individual IRQ handlers to all
> available lines. The later method assigns the _common_ handler to all
> the lines. The common handler already calls the Safety IRQ handler -
> stmmac_safety_feat_interrupt(). So should the safety IRQ line is
> separately available it's possible to have the Safety IRQ handlers
> executed concurrently - in framework of the common IRQ events handling
> (if safety IRQ is raised during the common IRQ being handled) and
> individual Safety IRQ. It's prune to the race condition I pointed out
> to in my message above. Did you consider that problem?
> 
>> Also, we need the sfty IRQ handling as soon as the fault occured & that can only be handled if we have handler attached with sfty IRQ.
>> stmmac_interrupt() will only be triggerd when interrupt triggered for rx/tx packet .
>> while registerting with sfty IRQ will get triggered as soon as emac HW detect the fault. 
> 
> Please read my comment more carefully. The safety IRQ can be raised
> during the common IRQ handling, thus the
> stmmac_safety_feat_interrupt() method might get to be concurrently
> executed.
> 
> -Serge(y)
> 
>>    
>>>> +		if (unlikely(ret < 0)) {
>>>> +			netdev_err(priv->dev,
>>>> +				   "%s: ERROR: allocating the sfty IRQ %d (%d)\n",
>>>> +				   __func__, priv->sfty_irq, ret);
>>>> +			irq_err = REQ_IRQ_ERR_SFTY;
>>>> +			goto irq_error;
>>>> +		}
>>>> +	}
>>>> +
>>>>  	return 0;
>>>>  
>>>>  irq_error:
>>>> @@ -7462,6 +7498,7 @@ int stmmac_dvr_probe(struct device *device,
>>>>  	priv->dev->irq = res->irq;
>>>>  	priv->wol_irq = res->wol_irq;
>>>>  	priv->lpi_irq = res->lpi_irq;
>>>> +	priv->sfty_irq = res->sfty_irq;
>>>>  	priv->sfty_ce_irq = res->sfty_ce_irq;
>>>>  	priv->sfty_ue_irq = res->sfty_ue_irq;
>>>>  	for (i = 0; i < MTL_MAX_RX_QUEUES; i++)
>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>>>> index 70eadc83ca68..ab250161fd79 100644
>>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>>>> @@ -743,6 +743,14 @@ int stmmac_get_platform_resources(struct platform_device *pdev,
>>>>  		dev_info(&pdev->dev, "IRQ eth_lpi not found\n");
>>>>  	}
>>>>  
>>>> +	stmmac_res->sfty_irq =
>>>> +		platform_get_irq_byname_optional(pdev, "sfty");
>>>> +	if (stmmac_res->sfty_irq < 0) {
>>>> +		if (stmmac_res->sfty_irq == -EPROBE_DEFER)
>>>> +			return -EPROBE_DEFER;
>>>> +		dev_info(&pdev->dev, "IRQ safety IRQ not found\n");
>>>> +	}
>>>> +
>>>>  	stmmac_res->addr = devm_platform_ioremap_resource(pdev, 0);
>>>>  
>>>>  	return PTR_ERR_OR_ZERO(stmmac_res->addr);
>>>> -- 
>>>> 2.25.1
>>>>
>>>>