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Message-ID: <ccd8b282-107b-ea74-184b-34f72f07866f@quicinc.com>
Date:   Sun, 25 Sep 2022 07:21:36 +0530
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Subject: Re: [PATCH v7 2/5] PCI: qcom: Add retry logic for link to be stable
 in either L1.1 or L1.2
Content-Language: en-US
To:     Vinod Koul <vkoul@kernel.org>
CC:     <helgaas@kernel.org>, <linux-pci@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <mka@chromium.org>, <quic_vbadigan@quicinc.com>,
        <quic_hemantk@quicinc.com>, <quic_nitegupt@quicinc.com>,
        <quic_skananth@quicinc.com>, <quic_ramkri@quicinc.com>,
        <manivannan.sadhasivam@linaro.org>, <swboyd@chromium.org>,
        <dmitry.baryshkov@linaro.org>, <svarbanov@mm-sol.com>,
        <agross@kernel.org>, <andersson@kernel.org>,
        <konrad.dybcio@somainline.org>, <lpieralisi@kernel.org>,
        <robh@kernel.org>, <kw@linux.com>, <bhelgaas@google.com>,
        <linux-phy@lists.infradead.org>, <kishon@ti.com>,
        <mturquette@baylibre.com>, <linux-clk@vger.kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>
References: <1663669347-29308-1-git-send-email-quic_krichai@quicinc.com>
 <1663669347-29308-3-git-send-email-quic_krichai@quicinc.com>
 <Yy6eJnXUMZk4i2PC@matsya>
From:   Krishna Chaitanya Chundru <quic_krichai@quicinc.com>
In-Reply-To: <Yy6eJnXUMZk4i2PC@matsya>
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On 9/24/2022 11:35 AM, Vinod Koul wrote:
> On 20-09-22, 15:52, Krishna chaitanya chundru wrote:
>> When link is in L1ss(L1.1 or L1.2), all the clocks will gate off and there
>> will be no activity on the link. At that point clocks and phy
>> can be turned off. If clocks got disabled before link enters
>> L1ss the PCIe link goes down.
>>
>> Few endpoints are taking time more time to settle the link in L1 substates.
>> When we check the traffic in protocol analyzer, we see some DLLP packets
>> going on still. So Wait for max time of 200ms for the link to be stable in
>> L1 substates.
>>
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
>> ---
>> changes since v6:
>> 	- updated comments.
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 46 ++++++++++++++++++++++++++--------
>>   1 file changed, 35 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index 3f5424a..7a6f69e 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -1809,23 +1809,47 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>   static int __maybe_unused qcom_pcie_pm_suspend(struct qcom_pcie *pcie)
>>   {
>>   	u32 val;
>> +	ktime_t timeout, start;
>>   	struct dw_pcie *pci = pcie->pci;
>>   	struct device *dev = pci->dev;
>>   
>> -	/* if the link is not active turn off clocks */
>> -	if (!dw_pcie_link_up(pci)) {
>> -		dev_dbg(dev, "Link is not active\n");
>> -		goto suspend;
>> -	}
>> +	/*
>> +	 * When link is in L1ss, all the clocks will gate off and
>> +	 * there will be no activity on the link. At that point clocks
>> +	 * and phy can be turned off. If clocks got disabled before
>> +	 * link enters L1ss the PCIe link goes down.
>> +	 *
>> +	 * Few endpoints are taking time more time to settle the link
>> +	 * in L1ss. Wait for max of 200ms for the link to be stable in
>> +	 * L1ss.
>> +	 */
>> +	start = ktime_get();
>> +	/* Wait max 200 ms */
>> +	timeout = ktime_add_ms(start, 200);
>> +
>> +	while (1) {
>> +		/* if the liink is not active turn off clocks */
>> +		if (!dw_pcie_link_up(pci)) {
>> +			dev_dbg(dev, "Link is not active\n");
>> +			break;
>> +		}
>>   
>> -	/* if the link is not in l1ss don't turn off clocks */
>> -	val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
>> -	if (!(val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
>> -		dev_warn(dev, "Link is not in L1ss\n");
>> -		return 0;
>> +		/* if the link is not in l1ss don't turn off clocks */
>> +		val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
>> +		if ((val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
>> +			dev_dbg(dev, "Link enters L1ss after %lld  ms\n",
>> +					ktime_to_ms(ktime_get() - start));
>> +			break;
>> +		}
>> +
>> +		if (ktime_after(ktime_get(), timeout)) {
>> +			dev_warn(dev, "Link is not in L1ss\n");
>> +			return 0;
>> +		}
>> +
> ugh, why not use readl_poll_timeout()?
As this is called from the syscore ops, all the interrupts will be 
disabled by the time the execution reaches here.
readl_poll_timeout uses interrupt internally and cause some issues.

So we are using this method instead of readl_poll_timeout.
>
>> +		udelay(1000);
>>   	}
>>   
>> -suspend:
>>   	if (pcie->cfg->ops->suspend)
>>   		pcie->cfg->ops->suspend(pcie);
>>   
>> -- 
>> 2.7.4