[Arm-dev] [PATCH] PCI/ASPM: Don't retrain link if ASPM not possible.

Merged. This will be available in the next update.

On 12/12/2016 02:29 AM, Vadim Lomovtsev wrote:
> Hi Jim,
> 
> Could you please consider this patch to be applied to 7.3 kernel build?
> 
> WBR,
> Vadim
> 
> On Mon, Dec 12, 2016 at 12:18:59AM -0800, Vadim Lomovtsev wrote:
>> From: David Daney <david.daney at cavium.com>
>>
>> Some (defective) PCIe devices are not able to reliably do link
>> retraining.
>>
>> Check to see if ASPM is possible between link partners before
>> configuring common clocking, and doing the resulting link retraining.
>> If ASPM is not possible, there is no reason to risk losing access to a
>> device due to an unnecessary link retraining.
>>
>> Signed-off-by: David Daney <david.daney at cavium.com>
>> Signed-off-by: Vadim Lomovtsev <Vadim.Lomovtsev at caviumnetworks.com>
>> ---
>>  drivers/pci/pcie/aspm.c | 18 ++++++++++++++++--
>>  1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>> index 2dfe7fd..abad79e 100644
>> --- a/drivers/pci/pcie/aspm.c
>> +++ b/drivers/pci/pcie/aspm.c
>> @@ -351,12 +351,26 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
>>  		return;
>>  	}
>>  
>> +	/* Get upstream/downstream components' register state */
>> +	pcie_get_aspm_reg(parent, &upreg);
>> +	child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
>> +	pcie_get_aspm_reg(child, &dwreg);
>> +
>> +	/*
>> +	 * If ASPM not supported, don't mess with the clocks and link,
>> +	 * bail out now.
>> +	 */
>> +	if (!(upreg.support & dwreg.support))
>> +		return;
>> +
>>  	/* Configure common clock before checking latencies */
>>  	pcie_aspm_configure_common_clock(link);
>>  
>> -	/* Get upstream/downstream components' register state */
>> +	/*
>> +	 * Re-read upstream/downstream components' register state
>> +	 * after clock configuration
>> +	 */
>>  	pcie_get_aspm_reg(parent, &upreg);
>> -	child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
>>  	pcie_get_aspm_reg(child, &dwreg);
>>  
>>  	/*
>> -- 
>> 2.5.5
>>

-- 
Jim Perrin
The CentOS Project | http://www.centos.org
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