Re: [PATCH v6 06/18] PCI: designware-ep: Add generic function for raising MSI irq

[Kishon Vijay Abraham I <kishon@ti.com>]

Hi Niklas,

On Thursday 28 December 2017 03:59 AM, Niklas Cassel wrote:
> On Tue, Dec 26, 2017 at 06:20:54PM +0530, Kishon Vijay Abraham I wrote:
>> Hi Niklas,
> 
> Hello Kishon
> 
>>
>> On Wednesday 20 December 2017 04:59 AM, Niklas Cassel wrote:
>>> Add a generic function for raising MSI irqs that can be used by all
>>> DWC based controllers.
>>>
>>> Note that certain controllers, like DRA7xx, have a special convenience
>>> register for raising MSI irqs that doesn't require you to explicitly map
>>> the MSI address. Therefore, it is likely that certain drivers will
>>> not use this generic function, even if they can.
>>>
>>> Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
>>> ---
>>>  drivers/pci/dwc/pcie-designware-ep.c | 35 +++++++++++++++++++++++++++++++++++
>>>  drivers/pci/dwc/pcie-designware.h    |  9 +++++++++
>>>  2 files changed, 44 insertions(+)
>>>
>>> diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
>>> index 700ed2f4becf..c5aa1cac5041 100644
>>> --- a/drivers/pci/dwc/pcie-designware-ep.c
>>> +++ b/drivers/pci/dwc/pcie-designware-ep.c
>>> @@ -282,6 +282,41 @@ static const struct pci_epc_ops epc_ops = {
>>>  	.stop			= dw_pcie_ep_stop,
>>>  };
>>>  
>>> +int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep,
>>> +			     u8 interrupt_num)
>>> +{
>>> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>>> +	struct pci_epc *epc = ep->epc;
>>> +	u16 msg_ctrl, msg_data;
>>> +	u32 msg_addr_lower, msg_addr_upper;
>>> +	u64 msg_addr;
>>> +	bool has_upper;
>>> +	int ret;
>>> +
>>> +	/* Raise MSI per the PCI Local Bus Specification Revision 3.0, 6.8.1. */
>>> +	msg_ctrl = dw_pcie_readw_dbi(pci, MSI_MESSAGE_CONTROL);
>>> +	has_upper = !!(msg_ctrl & PCI_MSI_FLAGS_64BIT);
>>> +	msg_addr_lower = dw_pcie_readl_dbi(pci, MSI_MESSAGE_ADDR_L32);
>>> +	if (has_upper) {
>>> +		msg_addr_upper = dw_pcie_readl_dbi(pci, MSI_MESSAGE_ADDR_U32);
>>> +		msg_data = dw_pcie_readw_dbi(pci, MSI_MESSAGE_DATA_64);
>>> +	} else {
>>> +		msg_addr_upper = 0;
>>> +		msg_data = dw_pcie_readw_dbi(pci, MSI_MESSAGE_DATA_32);
>>> +	}
>>> +	msg_addr = ((u64) msg_addr_upper) << 32 | msg_addr_lower;
>>> +	ret = dw_pcie_ep_map_addr(epc, ep->msi_mem_phys, msg_addr,
>>> +				  epc->mem->page_size);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	writel(msg_data | (interrupt_num - 1), ep->msi_mem);
>>
>> Shouldn't this be msg_data + (interrupt_num - 1)?
> 
> I'm not quite sure about this, but if there is a pending irq,
> not yet processed by the RC, the msg_data we read out in this
> function should have a bit set, matching the pending irq.

IIUC, the msg_data that we read here should not depend on the pending irq on
the RC side. msg_data should have the starting MSI vector number assigned by RC
for that EP device. (msg.data = pos; in dw_msi_setup_msg() also seem to suggest
the same).
> 
> If that irq is the same as the irq we are trying to raise,
> doing an addition will produce a bogus vector number,
> but a bitwise or should work.

if msg_data has the starting MSI vector, doing an addition should get to the
correct MSI vector.
> 
> For that reason, I think that doing bitwise or seems safer.
> However, other than this case, I don't see why it should
> matter if we do an addition or a bitwise or.
> 
> Are you having some problem with the code?
> It seems to be working fine on ARTPEC-6:
> 
> # ./pcitest -m 1
> MSI1:           OKAY
> # ./pcitest -m 2
> MSI2:           OKAY
> # ./pcitest -m 3
> MSI3:           OKAY
> # ./pcitest -m 4
> MSI4:           OKAY
> # ./pcitest -m 5
> MSI5:           OKAY
> # ./pcitest -m 6
> MSI6:           OKAY
> # ./pcitest -m 7
> MSI7:           OKAY
> # ./pcitest -m 8
> MSI8:           OKAY
> # ./pcitest -m 9
> MSI9:           OKAY
> # cat /proc/interrupts | grep -i msi
>  82:          9          0     GIC-0 180 Level     artpec6-pcie-msi
> 188:          1          0   PCI-MSI  16 Edge      pci-endpoint-test
> 189:          1          0   PCI-MSI  17 Edge      pci-endpoint-test
> 190:          1          0   PCI-MSI  18 Edge      pci-endpoint-test
> 191:          1          0   PCI-MSI  19 Edge      pci-endpoint-test
> 192:          1          0   PCI-MSI  20 Edge      pci-endpoint-test
> 193:          1          0   PCI-MSI  21 Edge      pci-endpoint-test
> 194:          1          0   PCI-MSI  22 Edge      pci-endpoint-test
> 195:          1          0   PCI-MSI  23 Edge      pci-endpoint-test
> 196:          1          0   PCI-MSI  24 Edge      pci-endpoint-test
> 197:          0          0   PCI-MSI  25 Edge      pci-endpoint-test
> 198:          0          0   PCI-MSI  26 Edge      pci-endpoint-test
> 199:          0          0   PCI-MSI  27 Edge      pci-endpoint-test
> 200:          0          0   PCI-MSI  28 Edge      pci-endpoint-test
> 201:          0          0   PCI-MSI  29 Edge      pci-endpoint-test
> 202:          0          0   PCI-MSI  30 Edge      pci-endpoint-test
> 203:          0          0   PCI-MSI  31 Edge      pci-endpoint-test
> 
> From EP:
> irq: 1 read msg_data: 0x10 writing: 0x10
> irq: 2 read msg_data: 0x10 writing: 0x11
> irq: 3 read msg_data: 0x10 writing: 0x12
> irq: 4 read msg_data: 0x10 writing: 0x13
> irq: 5 read msg_data: 0x10 writing: 0x14
> irq: 6 read msg_data: 0x10 writing: 0x15
> irq: 7 read msg_data: 0x10 writing: 0x16
> irq: 8 read msg_data: 0x10 writing: 0x17
> irq: 9 read msg_data: 0x10 writing: 0x18

since your msg_data is 0x10, you are not facing the issue. What if it's 0x1? In
my case If I have Gustavo's patch series applied, msg_data has a value of 0x1
and I don't get certain MSI interrupts.

Thanks
Kishon