linux-kernel - Re: [PATCH 1/8] bindings: PCI: designware: Example update

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Date:   Fri, 6 Apr 2018 11:53:47 +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>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/8] bindings: PCI: designware: Example update

Hi,

On Tuesday 03 April 2018 06:43 PM, Gustavo Pimentel wrote:
> Hi Kishon,
> 
> On 03/04/2018 11:53, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Tuesday 03 April 2018 04:22 PM, Kishon Vijay Abraham I wrote:
>>>
>>>
>>> On Tuesday 03 April 2018 04:03 PM, Gustavo Pimentel wrote:
>>>> Hi Kishon,
>>>>
>>>> On 02/04/2018 06:23, Kishon Vijay Abraham I wrote:
>>>>> Hi,
>>>>>
>>>>> On Wednesday 28 March 2018 05:08 PM, Gustavo Pimentel wrote:
>>>>>> Changes the IP registers size to accommodate the ATU unroll space.
>>>>>>
>>>>>> Replaces "ctrlreg" reg-name by "dbi" to be coherent with similar drivers.
>>>>>>
>>>>>> Replaces the pcie base address example by a real pcie base address in use.
>>>>>>
>>>>>> Signed-off-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
>>>>>> ---
>>>>>>  Documentation/devicetree/bindings/pci/designware-pcie.txt | 12 ++++++------
>>>>>>  1 file changed, 6 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/pci/designware-pcie.txt b/Documentation/devicetree/bindings/pci/designware-pcie.txt
>>>>>> index 1da7ade..6300762 100644
>>>>>> --- a/Documentation/devicetree/bindings/pci/designware-pcie.txt
>>>>>> +++ b/Documentation/devicetree/bindings/pci/designware-pcie.txt
>>>>>> @@ -1,7 +1,8 @@
>>>>>>  * Synopsys DesignWare PCIe interface
>>>>>>  
>>>>>>  Required properties:
>>>>>> -- compatible: should contain "snps,dw-pcie" to identify the core.
>>>>>> +- compatible:
>>>>>> +	"snps,dw-pcie" for RC mode;
>>>>>
>>>>> I think irrespective of RC mode or EP mode, "snps,dw-pcie" can be used to
>>>>> identify the pcie core?
>>>>
>>>> I guess so. What you suggest? I was just folling the same guideline present
>>>> here: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2017_11_3_310&d=DwIC-g&c=DPL6_X_6JkXFx7AXWqB0tg&r=bkWxpLoW-f-E3EdiDCCa0_h0PicsViasSlvIpzZvPxs&m=G1MqB_DY6ZwWtvS60L9PZMHnMe6rClMnrakAyQT_hDc&s=BhQYkrcp6y3QkD23qn1I6lU882BDUfLiXjBVWQ91cmg&e=
>>>
>>> Okay, I think you should have
>>> "snps,dw-pcie-rc", "snps,dw-pcie" for RC mode;
>>>
>>> and in the later patch
>>> "snps,dw-pcie-ep", "snps,dw-pcie" for EP mode;
>>>
> 
> Ok, I'll change it.
> 
>>>>
>>>>>>  - reg: Should contain the configuration address space.
>>>>>>  - reg-names: Must be "config" for the PCIe configuration space.
>>>>>>      (The old way of getting the configuration address space from "ranges"
>>>>>> @@ -41,11 +42,11 @@ EP mode:
>>>>>>  
>>>>>>  Example configuration:
>>>>>>  
>>>>>> -	pcie: pcie@...ff000 {
>>>>>> +	pcie: pcie@...00000 {
>>>>>>  		compatible = "snps,dw-pcie";
>>>>>> -		reg = <0xdffff000 0x1000>, /* Controller registers */
>>>>>> -		      <0xd0000000 0x2000>; /* PCI config space */
>>>>>> -		reg-names = "ctrlreg", "config";
>>>>>> +		reg = <0xdfc00000 0x302000>, /* IP registers */
>>>>>
>>>>> which version of synopsys IP is this. I think the ideal thing to do here is to
>>>>> have a separate register space for iATU.
>>>>
>>>> I also agree with that. The unroll iATU was introduced on Synopsys IP version
>>>> 4.80 and the kernel patch was release on 2016-08-10
>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__patchwork.ozlabs.org_patch_657796_&d=DwIC-g&c=DPL6_X_6JkXFx7AXWqB0tg&r=bkWxpLoW-f-E3EdiDCCa0_h0PicsViasSlvIpzZvPxs&m=G1MqB_DY6ZwWtvS60L9PZMHnMe6rClMnrakAyQT_hDc&s=EgKKDbg4ywCxu4-lG_scYAgPMnxirsjS0uSS7SzBTeM&e=
>>>> However a separate register space for iATU implies some extra code do handle it
>>>> (and of course some tests) that don't fit into this patch series, in my point of
>>>> view. Can this task enter in the backlog in order to be done in another patch
>>>> series?
>>>
>>> Yes sure. I think we should also make sure existing binding doesn't break.
> 
> I'll remove the any iATU unroll reference or change from this patch to avoid any
> confusion.

No, I think it's fine to have iATU unroll reference (since kernel also seems to
support iATU unroll).

What I meant is, we should add more flexibility on defining iATU address space
(while making sure it doesn't break existing binding).

I'm okay with this patch once you fix the compatible comment but in general
this is what I'd like to have (in a future patch)

*)  Add a new compatible "snps,dw-pcie-4.80";
*) In the kernel "iatu_unroll_enabled" should be set based on the above compatible
*) Define the a new reg space for iATU in 4.80

And these have to be done in a way it doesn't break existing binding.

Thanks
Kishon