From: "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: bhelgaas@google.com, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org, ashok.raj@intel.com,
dan.j.williams@intel.com, keith.busch@intel.com,
knsathya@kernel.org, Lukas Wunner <lukas@wunner.de>
Subject: Re: [PATCH v1 1/1] PCI: pciehp: Skip DLLSC handling if DPC is triggered
Date: Fri, 12 Mar 2021 15:26:39 -0800 [thread overview]
Message-ID: <7c64f84b-906a-7adf-901e-05492779a3a3@linux.intel.com> (raw)
In-Reply-To: <20210312231416.GA2304029@bjorn-Precision-5520>
On 3/12/21 3:14 PM, Bjorn Helgaas wrote:
> On Fri, Mar 12, 2021 at 02:11:03PM -0800, Kuppuswamy, Sathyanarayanan wrote:
>> On 3/12/21 1:33 PM, Bjorn Helgaas wrote:
>>> On Mon, Mar 08, 2021 at 10:34:10PM -0800, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>>>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>
>>>> +bool is_dpc_reset_active(struct pci_dev *dev)
>>>> +{
>>>> + struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
>>>> + u16 status;
>>>> +
>>>> + if (!dev->dpc_cap)
>>>> + return false;
>>>> +
>>>> + /*
>>>> + * If DPC is owned by firmware and EDR is not supported, there is
>>>> + * no race between hotplug and DPC recovery handler. So return
>>>> + * false.
>>>> + */
>>>> + if (!host->native_dpc && !IS_ENABLED(CONFIG_PCIE_EDR))
>>>> + return false;
>>>> +
>>>> + if (atomic_read_acquire(&dev->dpc_reset_active))
>>>> + return true;
>>>> +
>>>> + pci_read_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_STATUS, &status);
>>>> +
>>>> + return !!(status & PCI_EXP_DPC_STATUS_TRIGGER);
>>>
>>> I know it's somewhat common in drivers/pci/, but I'm not really a
>>> big fan of "!!".
>> I can change it to use ternary operator.
>> (status & PCI_EXP_DPC_STATUS_TRIGGER) ? true : false;
>
> Ternary isn't terrible, but what's wrong with:
>
> if (status & PCI_EXP_DPC_STATUS_TRIGGER)
> return true;
> return false;
I am fine with above format.
>
> which matches the style of the rest of the function.
>
> Looking at this again, we return "true" if either dpc_reset_active or
> PCI_EXP_DPC_STATUS_TRIGGER. I haven't worked this all out, but that
> pattern feels racy. I guess the thought is that if
> PCI_EXP_DPC_STATUS_TRIGGER is set, dpc_reset_link() will be invoked
> soon and we don't want to interfere?
Yes, the reason for checking dpc_reset_active before
PCI_EXP_DPC_STATUS_TRIGGER is because, we want suppress DLLSC events
till link comes back or it times out.
137 atomic_inc_return_acquire(&pdev->dpc_reset_active);
138
139 pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS,
140 PCI_EXP_DPC_STATUS_TRIGGER);
141
142 if (!pcie_wait_for_link(pdev, true)) {
143 pci_info(pdev, "Data Link Layer Link Active not set in 1000 msec\n");
144 status = PCI_ERS_RESULT_DISCONNECT;
145 }
146
147 atomic_dec_return_release(&pdev->dpc_reset_active);
>
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
next prev parent reply other threads:[~2021-03-12 23:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 6:34 [PATCH v1 1/1] PCI: pciehp: Skip DLLSC handling if DPC is triggered sathyanarayanan.kuppuswamy
2021-03-12 21:33 ` Bjorn Helgaas
2021-03-12 22:11 ` Kuppuswamy, Sathyanarayanan
2021-03-12 23:14 ` Bjorn Helgaas
2021-03-12 23:26 ` Kuppuswamy, Sathyanarayanan [this message]
2021-03-13 0:37 ` Dan Williams
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