Re: [PATCH 3/3] PCI: designware: Move interrupt acking into the proper callback

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

Hi Lorenzo,

On 11/12/18 6:05 PM, Lorenzo Pieralisi wrote:
> On Fri, Dec 07, 2018 at 03:43:00PM +0530, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On 07/12/18 3:15 PM, Marc Zyngier wrote:
>>> On 07/12/2018 08:12, Kishon Vijay Abraham I wrote:
>>>> Hi Marc,
>>>>
>>>> On 04/12/18 7:15 PM, Marc Zyngier wrote:
>>>>> On Tue, 4 Dec 2018 15:50:32 +0530
>>>>> Kishon Vijay Abraham I <kishon@ti.com> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On 14/11/18 4:27 AM, Marc Zyngier wrote:
>>>>>>> The write to the status register is really an ACK for the HW,
>>>>>>> and should be treated as such by the driver. Let's move it to the
>>>>>>> irq_ack callback, which will prevent people from moving it around
>>>>>>> in order to paper over other bugs.
>>>>>>>
>>>>>>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>>>>>>> ---
>>>>>>>  drivers/pci/controller/dwc/pcie-designware-host.c | 13 +++++++------
>>>>>>>  1 file changed, 7 insertions(+), 6 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
>>>>>>> index 0a76948ed49e..f06e67c60593 100644
>>>>>>> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
>>>>>>> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
>>>>>>> @@ -99,9 +99,6 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
>>>>>>>  					       (i * MAX_MSI_IRQS_PER_CTRL) +
>>>>>>>  					       pos);
>>>>>>>  			generic_handle_irq(irq);
>>>>>>> -			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS +
>>>>>>> -						(i * MSI_REG_CTRL_BLOCK_SIZE),
>>>>>>> -					    4, 1 << pos);
>>>>>>>  			pos++;
>>>>>>>  		}
>>>>>>>  	}
>>>>>>> @@ -200,14 +197,18 @@ static void dw_pci_bottom_unmask(struct irq_data *data)
>>>>>>>  
>>>>>>>  static void dw_pci_bottom_ack(struct irq_data *d)
>>>>>>>  {
>>>>>>> -	struct msi_desc *msi = irq_data_get_msi_desc(d);
>>>>>>> -	struct pcie_port *pp;
>>>>>>> +	struct pcie_port *pp  = irq_data_get_irq_chip_data(d);
>>>>>>> +	unsigned int res, bit, ctrl;
>>>>>>>  	unsigned long flags;
>>>>>>>  
>>>>>>> -	pp = msi_desc_to_pci_sysdata(msi);
>>>>>>> +	ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
>>>>>>> +	res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
>>>>>>> +	bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
>>>>>>>  
>>>>>>>  	raw_spin_lock_irqsave(&pp->lock, flags);
>>>>>>>  
>>>>>>> +	dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + res, 4, 1 << bit);  
>>>>>>
>>>>>> This register should be written only if msi_irq_ack callback is not populated
>>>>>> similar to other dw_pci_bottom_*() functions.
>>>>>
>>>>> Why? This was so far unconditionally written, and my understanding is
>>>>> that without this write, no further MSI can be delivered.
>>>>
>>>> Not all platforms invoke dw_handle_msi_irq() for handling MSI irq.
>>>>
>>>> Platforms that doesn't use the MSI functionality of Designware makes use of the
>>>> various callbacks like msi_irq_ack, msi_host_init etc., Keystone has MSI
>>>> controller in the Keystone wrapper, AM654 uses GIC ITS etc.,
>>>>
>>>> The platforms that doesn't use MSI functionality of Designware doesn't have to
>>>> write to Designware's MSI configuration registers.
>>>
>>> Let's be clear: a platform that doesn't use the DW MSI functionality
>>> should never get anywhere this code. If they do, then that's a terrible
>>> bug, and it should be fixed by making the TI stuff standalone instead of
>>> calling into the internals.
>>
>> That makes sense to me. We can start by removing msi_set_irq, msi_clear_irq and
>> msi_irq_ack callbacks from dw_pcie_host_ops.
>>
>> This functionality can be added directly in keystone driver.
>>>
>>> Frankly, this whole thing should be marked as BROKEN until it is sorted
>>> out for good.
>>
>> Maybe remove those callbacks and make only Keystone broken?
> 
> Hi Kishon, Murali,
> 
> Is it possible to rework keystone as discussed on this thread on top of
> my pci/dwc-msi branch please ?

yeah, I'll work on that.

Thanks
Kishon