Re: [PATCH] PCI/DPC: Fix INT legacy interrupt in dpc_irq

From: poza@codeaurora.org
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	Dongdong Liu <liudongdong3@huawei.com>,
	Keith Busch <keith.busch@intel.com>, Wei Zhang <wzhang@fb.com>,
	Sinan Kaya <okaya@codeaurora.org>,
	Timur Tabi <timur@codeaurora.org>
Subject: Re: [PATCH] PCI/DPC: Fix INT legacy interrupt in dpc_irq
Date: Thu, 01 Mar 2018 21:17:47 +0530	[thread overview]
Message-ID: <d759fe9efb8e5ece4097375e97772565@codeaurora.org> (raw)
In-Reply-To: <20180301153802.GD13722@bhelgaas-glaptop.roam.corp.google.com>

On 2018-03-01 21:08, Bjorn Helgaas wrote:
> Hi Oza,
> 
> On Wed, Jan 31, 2018 at 09:48:55PM +0530, Oza Pawandeep wrote:
>> Current dpc driver acknowledge the interrupt in deferred work, which 
>> works
>> okay since LPI are edge triggered.
>> But when RP does not have MSI support, port service driver falls back 
>> to
>> legacy GIC SPI interrupts, and with current code we do not acknowledge 
>> the
>> interrupt and we get dpc interrupt storm.
>> This patch acknowledges the interrupt in interrupt handler.
> 
> Would you mind rephrasing this changelog in generic PCIe terms?  E.g.,
> "LPI" and "GIC SPI" are meaningless to me (I assume they're
> arm64-specific things), but I don't think it's any arm64-specific
> thing that motivates this change.  IIUC, the issue should occur any
> time we're not using MSI, so we should be able to describe it in
> purely PCIe terms.
> 
> s/dpc/DPC/ in text.
> 
> It looks like this changelog is intended to be multiple paragraphs; if
> so, please leave a blank line between them.  It's a little awkward to
> infer "this is a new paragraph" from the fact that "the previous line
> didn't look full" :)
> 
> Please rebase to my "master" branch (v4.16-rc1).  There was some minor
> change that made this not apply cleanly.
> 

sure will do these changes and re-post the same.

Regards,
Oza.

>> Signed-off-by: Oza Pawandeep <poza@codeaurora.org>
>> 
>> diff --git a/drivers/pci/pcie/pcie-dpc.c b/drivers/pci/pcie/pcie-dpc.c
>> index 2d976a6..570b561 100644
>> --- a/drivers/pci/pcie/pcie-dpc.c
>> +++ b/drivers/pci/pcie/pcie-dpc.c
>> @@ -134,7 +134,7 @@ static void interrupt_event_handler(struct 
>> work_struct *work)
>>  	}
>> 
>>  	pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_STATUS,
>> -		PCI_EXP_DPC_STATUS_TRIGGER | PCI_EXP_DPC_STATUS_INTERRUPT);
>> +			      PCI_EXP_DPC_STATUS_TRIGGER);
>>  }
>> 
>>  static void dpc_rp_pio_print_tlp_header(struct device *dev,
>> @@ -277,6 +277,8 @@ static irqreturn_t dpc_irq(int irq, void *context)
>> 
>>  		schedule_work(&dpc->work);
>>  	}
>> +	pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_STATUS,
>> +			      PCI_EXP_DPC_STATUS_INTERRUPT);
>>  	return IRQ_HANDLED;
>>  }
>> 
>> --
>> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm 
>> Technologies, Inc.,
>> a Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a 
>> Linux Foundation Collaborative Project.
>> 