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

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Message-ID: <eeb3ace0-9206-efbf-f5db-97ccea0f47b7@ti.com>
Date:   Tue, 24 Apr 2018 16:54:20 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Gustavo Pimentel <gustavo.pimentel@...opsys.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,

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).

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
>