linux-kernel - Re: [RFC 01/10] PCI: dwc: Add MSI-X callbacks handler

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Date:   Thu, 26 Apr 2018 16:30:09 +0100
From:   Gustavo Pimentel <gustavo.pimentel@...opsys.com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "adouglas@...ence.com" <adouglas@...ence.com>,
        "niklas.cassel@...s.com" <niklas.cassel@...s.com>,
        "jesper.nilsson@...s.com" <jesper.nilsson@...s.com>
Cc:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 01/10] PCI: dwc: Add MSI-X callbacks handler


Hi Kishon,

On 24/04/2018 12:24, Kishon Vijay Abraham I wrote:
> Hi,
> 
> On Tuesday 24 April 2018 03:06 PM, Gustavo Pimentel wrote:
>> 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@...opsys.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.
> 
> It's just a helper function so it can directly take the base address of the
> configuration space as argument (in our case, it should be dbi_base).

I don't think it will bring much benefit to this particular scope at this time
being. In any case this could be improved later.

Regards,
Gustavo

> 
> Thanks
> Kishon
> 
>>
>> 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
>>