Re: [PATCH] PCI: dwc: skip MSI init if MSIs have been explicitly disabled

[Gustavo Pimentel <gustavo.pimentel@synopsys.com>]

On 28/02/2019 13:29, Lorenzo Pieralisi wrote:
> On Wed, Feb 27, 2019 at 05:52:19PM +0100, Lucas Stach wrote:
>> Since 7c5925afbc58 (PCI: dwc: Move MSI IRQs allocation to IRQ domains
>> hierarchical API) the MSI init claims one of the controller IRQs as a
>> chained IRQ line for the MSI controller. On some designs, like the i.MX6,
>> this line is shared with a PCIe legacy IRQ. When the line is claimed for
>> the MSI domain, any device trying to use this legacy IRQs will fail to
>> request this IRQ line.
>>
>> As MSI and legacy IRQs are already mutually exclusive on the DWC core,
>> as the core won't forward any legacy IRQs once any MSI has been enabled,
>> users wishing to use legacy IRQs already need to explictly disable MSI
>> support (usually via the pci=nomsi kernel commandline option). To avoid
>> any issues with MSI conflicting with legacy IRQs, just skip all of the
>> DWC MSI initalization, including the IRQ line claim, when MSI is disabled.
>>
>> Fixes: c5925afbc58
>>        (PCI: dwc: Move MSI IRQs allocation to IRQ domains hierarchical API)
>> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
>> Tested-by: Tim Harvey <tharvey@gateworks.com>
>> ---
>>  drivers/pci/controller/dwc/pcie-designware-host.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> I request Gustavo's ACK to proceed, thanks.
> 
> Lorenzo
> 
>> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
>> index 29a05759a294..f4a8494f616b 100644
>> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
>> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
>> @@ -433,7 +433,7 @@ int dw_pcie_host_init(struct pcie_port *pp)
>>  	if (ret)
>>  		pci->num_viewport = 2;
>>  
>> -	if (IS_ENABLED(CONFIG_PCI_MSI)) {
>> +	if (IS_ENABLED(CONFIG_PCI_MSI) && pci_msi_enabled()) {
>>  		/*
>>  		 * If a specific SoC driver needs to change the
>>  		 * default number of vectors, it needs to implement
>> -- 
>> 2.20.1
>>

Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>