linux-kernel - Re: [PATCH v11 04/11] PCI: brcmstb: Add suspend and resume pm

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Message-ID: <3c6a0acc-8966-fd38-1613-8da7bece81c7@gmail.com>
Date:   Thu, 10 Sep 2020 12:07:56 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jim Quinlan <james.quinlan@...adcom.com>,
        Rob Herring <robh@...nel.org>
Cc:     "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 04/11] PCI: brcmstb: Add suspend and resume pm_ops



On 9/10/2020 12:05 PM, Jim Quinlan wrote:
> On Thu, Sep 10, 2020 at 2:50 PM Rob Herring <robh@...nel.org> wrote:
>>
>> On Thu, Sep 10, 2020 at 10:42 AM Jim Quinlan <james.quinlan@...adcom.com> wrote:
>>>
>>> On Thu, Sep 10, 2020 at 11:56 AM Rob Herring <robh@...nel.org> wrote:
>>>>
>>>> On Mon, Aug 24, 2020 at 03:30:17PM -0400, Jim Quinlan wrote:
>>>>> From: Jim Quinlan <jquinlan@...adcom.com>
>>>>>
>>>>> Broadcom Set-top (BrcmSTB) boards typically support S2, S3, and S5 suspend
>>>>> and resume.  Now the PCIe driver may do so as well.
>>>>>
>>>>> Signed-off-by: Jim Quinlan <jquinlan@...adcom.com>
>>>>> Acked-by: Florian Fainelli <f.fainelli@...il.com>
>>>>> ---
>>>>>   drivers/pci/controller/pcie-brcmstb.c | 47 +++++++++++++++++++++++++++
>>>>>   1 file changed, 47 insertions(+)
>>>>>
>>>>> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
>>>>> index c2b3d2946a36..3d588ab7a6dd 100644
>>>>> --- a/drivers/pci/controller/pcie-brcmstb.c
>>>>> +++ b/drivers/pci/controller/pcie-brcmstb.c
>>>>> @@ -978,6 +978,47 @@ static void brcm_pcie_turn_off(struct brcm_pcie *pcie)
>>>>>        brcm_pcie_bridge_sw_init_set(pcie, 1);
>>>>>   }
>>>>>
>>>>> +static int brcm_pcie_suspend(struct device *dev)
>>>>> +{
>>>>> +     struct brcm_pcie *pcie = dev_get_drvdata(dev);
>>>>> +
>>>>> +     brcm_pcie_turn_off(pcie);
>>>>> +     clk_disable_unprepare(pcie->clk);
>>>>> +
>>>>> +     return 0;
>>>>> +}
>>>>> +
>>>>> +static int brcm_pcie_resume(struct device *dev)
>>>>> +{
>>>>> +     struct brcm_pcie *pcie = dev_get_drvdata(dev);
>>>>> +     void __iomem *base;
>>>>> +     u32 tmp;
>>>>> +     int ret;
>>>>> +
>>>>> +     base = pcie->base;
>>>>> +     clk_prepare_enable(pcie->clk);
>>>>> +
>>>>> +     /* Take bridge out of reset so we can access the SERDES reg */
>>>>> +     brcm_pcie_bridge_sw_init_set(pcie, 0);
>>>>> +
>>>>> +     /* SERDES_IDDQ = 0 */
>>>>> +     tmp = readl(base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
>>>>> +     u32p_replace_bits(&tmp, 0, PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK);
>>>>> +     writel(tmp, base + PCIE_MISC_HARD_PCIE_HARD_DEBUG);
>>>>> +
>>>>> +     /* wait for serdes to be stable */
>>>>> +     udelay(100);
>>>>
>>>> Really needs to be a spinloop?
>>>>
>>>>> +
>>>>> +     ret = brcm_pcie_setup(pcie);
>>>>> +     if (ret)
>>>>> +             return ret;
>>>>> +
>>>>> +     if (pcie->msi)
>>>>> +             brcm_msi_set_regs(pcie->msi);
>>>>> +
>>>>> +     return 0;
>>>>> +}
>>>>> +
>>>>>   static void __brcm_pcie_remove(struct brcm_pcie *pcie)
>>>>>   {
>>>>>        brcm_msi_remove(pcie);
>>>>> @@ -1087,12 +1128,18 @@ static int brcm_pcie_probe(struct platform_device *pdev)
>>>>>
>>>>>   MODULE_DEVICE_TABLE(of, brcm_pcie_match);
>>>>>
>>>>> +static const struct dev_pm_ops brcm_pcie_pm_ops = {
>>>>> +     .suspend_noirq = brcm_pcie_suspend,
>>>>> +     .resume_noirq = brcm_pcie_resume,
>>>>
>>>> Why do you need interrupts disabled? There's 39 cases of .suspend_noirq
>>>> and 1352 of .suspend in the tree.
>>>
>>> I will test switching this to  suspend_late/resume_early.
>>
>> Why not just the 'regular' flavor suspend/resume?
>>
>> Rob
> We must have our PCIe driver suspend last and resume first because our
> current driver turns off/on the power for the EPs.  Note that this
> code isn't in the driver as we are still figuring out a way to make it
> upstreamable.

The suspend/resume ordering should be guaranteed by the Linux device 
driver model though if not, this is a bug that ought to be fixed. The 
PCI bridge sits at the top of the pci_device list and all EPs should be 
child devices, so the suspend order should be from EPs down to the 
bridge, and the resume the converse.
-- 
Florian