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Subject: Re: [RFC 01/10] PCI: dwc: Add MSI-X callbacks handler
To:     Kishon Vijay Abraham I <kishon@ti.com>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
        "Joao.Pinto@synopsys.com" <Joao.Pinto@synopsys.com>,
        "jingoohan1@gmail.com" <jingoohan1@gmail.com>,
        "adouglas@cadence.com" <adouglas@cadence.com>,
        "niklas.cassel@axis.com" <niklas.cassel@axis.com>,
        "jesper.nilsson@axis.com" <jesper.nilsson@axis.com>
Cc:     "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <cover.1523379766.git.gustavo.pimentel@synopsys.com>
 <77b7b2687e9618d3f7d1f11c3fc6ecec9a9442ef.1523379766.git.gustavo.pimentel@synopsys.com>
 <0b7023d9-29c6-0993-07d3-b046d25b67ff@ti.com>
 <e2fe7d5f-9f57-0e67-d321-541ff4706792@synopsys.com>
 <0e8b8ce9-db12-1e11-3eb5-62f3fa686d59@ti.com>
From:   Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Message-ID: <16d237b2-0052-447e-13cb-bc2f15848be4@synopsys.com>
Date:   Tue, 24 Apr 2018 10:36:27 +0100
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Hi Kishon,

On 24/04/2018 08:07, Kishon Vijay Abraham I wrote:
> Hi,
> 
> On Monday 23 April 2018 03:06 PM, Gustavo Pimentel wrote:
>> Hi Kishon,
>>
>> On 16/04/2018 10:29, Kishon Vijay Abraham I wrote:
>>> Hi Gustavo,
>>>
>>> On Tuesday 10 April 2018 10:44 PM, Gustavo Pimentel wrote:
>>>> Changes the pcie_raise_irq function signature, namely the interrupt_num
>>>> variable type from u8 to u16 to accommodate the MSI-X maximum interrupts
>>>> of 2048.
>>>>
>>>> Implements a PCIe config space capability iterator function to search and
>>>> save the MSI and MSI-X pointers. With this method the code becomes more
>>>> generic and flexible.
>>>>
>>>> Implements MSI-X set/get functions for sysfs interface in order to change
>>>> the EP entries number.
>>>>
>>>> Implements EP MSI-X interface for triggering interruptions.
>>>>
>>>> Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
>>>> ---
>>>>  drivers/pci/dwc/pci-dra7xx.c           |   2 +-
>>>>  drivers/pci/dwc/pcie-artpec6.c         |   2 +-
>>>>  drivers/pci/dwc/pcie-designware-ep.c   | 145 ++++++++++++++++++++++++++++++++-
>>>>  drivers/pci/dwc/pcie-designware-plat.c |   6 +-
>>>>  drivers/pci/dwc/pcie-designware.h      |  23 +++++-
>>>>  5 files changed, 173 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
>>>> index ed8558d..5265725 100644
>>>> --- a/drivers/pci/dwc/pci-dra7xx.c
>>>> +++ b/drivers/pci/dwc/pci-dra7xx.c
>>>> @@ -369,7 +369,7 @@ static void dra7xx_pcie_raise_msi_irq(struct dra7xx_pcie *dra7xx,
>>>>  }
>>>>  
>>>>  static int dra7xx_pcie_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
>>>> -				 enum pci_epc_irq_type type, u8 interrupt_num)
>>>> +				 enum pci_epc_irq_type type, u16 interrupt_num)
>>>>  {
>>>>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>>>>  	struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci);
>>>> diff --git a/drivers/pci/dwc/pcie-artpec6.c b/drivers/pci/dwc/pcie-artpec6.c
>>>> index e66cede..96dc259 100644
>>>> --- a/drivers/pci/dwc/pcie-artpec6.c
>>>> +++ b/drivers/pci/dwc/pcie-artpec6.c
>>>> @@ -428,7 +428,7 @@ static void artpec6_pcie_ep_init(struct dw_pcie_ep *ep)
>>>>  }
>>>>  
>>>>  static int artpec6_pcie_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
>>>> -				  enum pci_epc_irq_type type, u8 interrupt_num)
>>>> +				  enum pci_epc_irq_type type, u16 interrupt_num)
>>>>  {
>>>>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>>>>  
>>>> diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
>>>> index 15b22a6..874d4c2 100644
>>>> --- a/drivers/pci/dwc/pcie-designware-ep.c
>>>> +++ b/drivers/pci/dwc/pcie-designware-ep.c
>>>> @@ -40,6 +40,44 @@ void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar)
>>>>  	__dw_pcie_ep_reset_bar(pci, bar, 0);
>>>>  }
>>>>  
>>>> +void dw_pcie_ep_find_cap_addr(struct dw_pcie_ep *ep)
>>>> +{
>>>
>>> This should be implemented in a generic way similar to pci_find_capability().
>>> It'll be useful when we try to implement other capabilities as well.
>>
>> Hum, what you suggest? Something implemented on the pci-epf-core?
> 
> yeah, Initially thought it could be implemented as a helper function in
> pci-epc-core so that both designware and cadence can use it.

That would be nice, however I couldn't find out how to access the config space,
through the pci_epf or pci_epc structs.

So, I reworked the functions like this:

(on pcie-designware-ep.c)

u8 __dw_pcie_ep_find_next_cap(struct dw_pcie *pci, u8 cap_ptr,
                              u8 cap)
{
        u8 cap_id, next_cap_ptr;
        u16 reg;

        reg = dw_pcie_readw_dbi(pci, cap_ptr);
        next_cap_ptr = (reg & 0xff00) >> 8;
        cap_id = (reg & 0x00ff);

        if (!next_cap_ptr || cap_id > PCI_CAP_ID_MAX)
                return 0;

        if (cap_id == cap)
                return cap_ptr;

        return __dw_pcie_ep_find_next_cap(pci, next_cap_ptr, cap);
}

u8 dw_pcie_ep_find_capability(struct dw_pcie *pci, u8 cap)
{
        u8 next_cap_ptr;
        u16 reg;

        reg = dw_pcie_readw_dbi(pci, PCI_CAPABILITY_LIST);
        next_cap_ptr = (reg & 0x00ff);

        if (!next_cap_ptr)
                return 0;

        return __dw_pcie_ep_find_next_cap(pci, next_cap_ptr, cap);
}

int dw_pcie_ep_init(struct dw_pcie_ep *ep)
{
[...]
        ep->msi_cap = dw_pcie_ep_find_capability(pci, PCI_CAP_ID_MSI);
        ep->msix_cap = dw_pcie_ep_find_capability(pci, PCI_CAP_ID_MSIX);
[...]
}

> 
> But do we really have to find the address like this? since all designware IP's
> will have a particular capability at a fixed address offset, why not follow use
> existing mechanism in dw_pcie_ep_get_msi?

The capabilities are not fixed to a specific address offset by default they
assume those values, but they can be easily change at design stage.

> 
> Or is it possible for a particular capability to have address offsets for
> different vendors? How is it for cadence?

Yes, it's possible to have different address offset for different vendors.

> 
> Thanks
> Kishon
> 

Thanks,
Gustavo