linux-kernel - Re: [RFC PATCH v2] PCI/portdrv: Only disable Bus Master on kexec reboot and connected PCI devices

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Date:   Mon, 14 Sep 2020 14:13:31 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Konstantin Khlebnikov <khlebnikov@...nvz.org>,
        Khalid Aziz <khalid.aziz@...cle.com>,
        Vivek Goyal <vgoyal@...hat.com>, oohall@...il.com,
        rafael.j.wysocki@...el.com, Xuefeng Li <lixuefeng@...ngson.cn>,
        Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] PCI/portdrv: Only disable Bus Master on kexec
 reboot and connected PCI devices

On 09/14/2020 12:06 PM, Lukas Wunner wrote:
> On Mon, Sep 14, 2020 at 04:29:10AM +0800, Tiezhu Yang wrote:
>> --- a/drivers/pci/pcie/portdrv_pci.c
>> +++ b/drivers/pci/pcie/portdrv_pci.c
>> @@ -143,6 +144,28 @@ static void pcie_portdrv_remove(struct pci_dev *dev)
>>   	}
>>   
>>   	pcie_port_device_remove(dev);
>> +	pci_disable_device(dev);
>> +}
>> +
>> +static void pcie_portdrv_shutdown(struct pci_dev *dev)
>> +{
>> +	if (pci_bridge_d3_possible(dev)) {
>> +		pm_runtime_forbid(&dev->dev);
>> +		pm_runtime_get_noresume(&dev->dev);
>> +		pm_runtime_dont_use_autosuspend(&dev->dev);
>> +	}
>> +
>> +	pcie_port_device_remove(dev);
>> +
>> +	/*
>> +	 * If this is a kexec reboot, turn off Bus Master bit on the
>> +	 * device to tell it to not continue to do DMA. Don't touch
>> +	 * devices in D3cold or unknown states.
>> +	 * If it is not a kexec reboot, firmware will hit the PCI
>> +	 * devices with big hammer and stop their DMA any way.
>> +	 */
>> +	if (kexec_in_progress && (dev->current_state <= PCI_D3hot))
>> +		pci_disable_device(dev);
> The last portion of this function is already executed afterwards by
> pci_device_shutdown().  You don't need to duplicate it here:
>
> device_shutdown()
>    dev->bus->shutdown() == pci_device_shutdown()
>      drv->shutdown() == pcie_portdrv_shutdown()
>        pci_disable_device()
>      pci_disable_device()

pcie_port_device_remove() deletes pci_disable_device(dev)  at the beginning of this patch.


diff 
<https://lore.kernel.org/linux-pci/CAAhV-H5-X9OcBe3iRxF8PnKW-0j_10FVqm8cbiqW2-Lv4mTTdQ@mail.gmail.com/T/#iZ2e.:..:1600028950-10644-1-git-send-email-yangtiezhu::40loongson.cn:0drivers:pci:pcie:portdrv_core.c> 
--git a/drivers/pci/pcie/portdrv_core.c 
b/drivers/pci/pcie/portdrv_core.c index 50a9522..1991aca 100644 --- 
a/drivers/pci/pcie/portdrv_core.c +++ b/drivers/pci/pcie/portdrv_core.c 
@@ -491,7 +491,6 @@ void pcie_port_device_remove(struct pci_dev *dev)   {
  	device_for_each_child(&dev->dev, NULL, remove_iter);
  	pci_free_irq_vectors(dev);
- pci_disable_device(dev);   }

>
> Thanks,
>
> Lukas