linux-kernel - Re: [PATCH v7 2/3] dwc: PCI: intel: PCIe RC controller driver

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Date:   Tue, 19 Nov 2019 03:54:48 +0000
From:   Jingoo Han <jingoohan1@...il.com>
To:     Dilip Kota <eswara.kota@...ux.intel.com>,
        "gustavo.pimentel@...opsys.com" <gustavo.pimentel@...opsys.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "andrew.murray@....com" <andrew.murray@....com>,
        "helgaas@...nel.org" <helgaas@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>,
        "martin.blumenstingl@...glemail.com" 
        <martin.blumenstingl@...glemail.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "andriy.shevchenko@...el.com" <andriy.shevchenko@...el.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "cheol.yong.kim@...el.com" <cheol.yong.kim@...el.com>,
        "chuanhua.lei@...ux.intel.com" <chuanhua.lei@...ux.intel.com>,
        "qi-ming.wu@...el.com" <qi-ming.wu@...el.com>,
        Han Jingoo <jingoohan1@...il.com>
Subject: Re: [PATCH v7 2/3] dwc: PCI: intel: PCIe RC controller driver



On 11/18/19, 10:15 PM, Dilip Kota wrote:
>On 11/19/2019 10:33 AM, Jingoo Han wrote:
>> On 11/18/19, 8:26 PM, Dilip Kota wrote:
>>> On 11/19/2019 12:40 AM, Jingoo Han wrote:
>>>> On 11/18/19, 2:58 AM, Dilip Kota wrote:
>>>>
>>>>> On 11/16/2019 4:40 AM, Jingoo Han wrote:
>>>>>> On 11/14/19, 9:31 PM, Dilip Kota wrote:
>>>>>>
>>>>>>> Add support to PCIe RC controller on Intel Gateway SoCs.
>>>>>>> PCIe controller is based of Synopsys DesignWare PCIe core.
>>>>>>>
>>>>>>> Intel PCIe driver requires Upconfigure support, Fast Training
>>>>>>> Sequence and link speed configurations. So adding the respective
>>>>>>> helper functions in the PCIe DesignWare framework.
>>>>>>> It also programs hardware autonomous speed during speed
>>>>>>> configuration so defining it in pci_regs.h.
>>>>>>>
>>>>>>> Signed-off-by: Dilip Kota <eswara.kota@...ux.intel.com>
>>>>>>> Reviewed-by: Andrew Murray <andrew.murray@....com>
>>>>>>> Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
>>>>>>> ---
>>>>>> [.....]
>>>>>>
>>>>>>>     drivers/pci/controller/dwc/Kconfig           |  10 +
>>>>>>>     drivers/pci/controller/dwc/Makefile          |   1 +
>>>>>>>     drivers/pci/controller/dwc/pcie-designware.c |  57 +++
>>>>>>>     drivers/pci/controller/dwc/pcie-designware.h |  12 +
>>>>>>>     drivers/pci/controller/dwc/pcie-intel-gw.c   | 542 +++++++++++++++++++++++++++
>>>>>>>     include/uapi/linux/pci_regs.h                |   1 +
>>>>>>>     6 files changed, 623 insertions(+)
>>>>>>>     create mode 100644 drivers/pci/controller/dwc/pcie-intel-gw.c
>>>>>>>
>>>>>>> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
>>>>>>> index 0ba988b5b5bc..fb6d474477df 100644
>>>>>>> --- a/drivers/pci/controller/dwc/Kconfig
>>>>>>> +++ b/drivers/pci/controller/dwc/Kconfig
>>>>>>> @@ -82,6 +82,16 @@ config PCIE_DW_PLAT_EP
>>>>>>>     	  order to enable device-specific features PCI_DW_PLAT_EP must be
>>>>>>>     	  selected.
>>>>>>>     
>>>>>>> +config PCIE_INTEL_GW
>>>>>>> +	bool "Intel Gateway PCIe host controller support"
>>>>>>> +	depends on OF && (X86 || COMPILE_TEST)
>>>>>>> +	select PCIE_DW_HOST
>>>>>>> +	help
>>>>>>> +	  Say 'Y' here to enable PCIe Host controller support on Intel
>>>>>>> +	  Gateway SoCs.
>>>>>>> +	  The PCIe controller uses the DesignWare core plus Intel-specific
>>>>>>> +	  hardware wrappers.
>>>>>>> +
>>>>>> Please add this config alphabetical order!
>>>>>> So, this config should be after 'config PCI_IMX6'.
>>>>>> There is no reason to put this config at the first place.
>>>>>>
>>>>>>>     config PCI_EXYNOS
>>>>>>>     	bool "Samsung Exynos PCIe controller"
>>>>>>>     	depends on SOC_EXYNOS5440 || COMPILE_TEST
>>>>>>> diff --git a/drivers/pci/controller/dwc/Makefile b/drivers/pci/controller/dwc/Makefile
>>>>>>> index b30336181d46..99db83cd2f35 100644
>>>>>>> --- a/drivers/pci/controller/dwc/Makefile
>>>>>>> +++ b/drivers/pci/controller/dwc/Makefile
>>>>>>> @@ -3,6 +3,7 @@ obj-$(CONFIG_PCIE_DW) += pcie-designware.o
>>>>>>>     obj-$(CONFIG_PCIE_DW_HOST) += pcie-designware-host.o
>>>>>>>     obj-$(CONFIG_PCIE_DW_EP) += pcie-designware-ep.o
>>>>>>>     obj-$(CONFIG_PCIE_DW_PLAT) += pcie-designware-plat.o
>>>>>>> +obj-$(CONFIG_PCIE_INTEL_GW) += pcie-intel-gw.o
>>>>>> Ditto.
>>>>> PCIE_INTEL_GW wouldnt come after PCI_IMX6, the complete Makefile and
>>>>> Kconfig are not in order,( PCI_* and PCIE_* are not in any order). So i
>>>>> just followed PCIE_DW and placed PCIE_INTEL_GW after PCIE_DW as I is
>>>>> after D (and i see PCI_* immediately after the PCIE_DW*, so i placed
>>>>> PCIE_INTEL_GW after PCIE_DW* and before PCI_*).
>>>> Hey, although some of them are not in order, you don't have a right to do so.
>>>> If some people do not follow the law, it does not mean that you can break the law.
>>>> Anyway, if you don't follow an alphabetical order, my answer is NACK.
>>>> Also, other people or I will send a patch to fix the order of other drivers.
>>> I am not against following the order. I kept PCIE_INTEL_GW after
>>> PCIE_DW* by checking the best possible order.
>>> As per the alphabetical order, i see all CONFIG_PCIE_* comes first and
>>> CONFIG_PCI_* follows. So, by following this, i placed PCIE_INTEL_GW
>>> after PCIE_DW* (for the same reason PCIE_INTEL_GW cannot be placed after
>>> PCI_IMX6).
>>> Even after re-ordering the Kconfig and Makefile, still PCIE_INTEL_GW
>>> comes after PCIE_DW_PLAT( and PCIE_HISI_STB).
>> Are you kidding me?
>>
>> Most PCIE_* drivers are located after PCI_*. Look at PCIE_QCOM, PCIE_ARMADA_8K,
>> PCIE_ARTPEC6, PCIE_KIRIN, PCIE_HISI_STB, PCIE_TEGRA194, PCIE_UNIPHIER, PCIE_AL.
>Ok, So the understanding is PCIE_DW* will be at top as they are 
>framework and then comes CONFIG_PCI_*, CONFIG_PCIE_*.

Yes, right.
Ah, I will explain the order of Kconfig options in the dwc directory.
The order is PCIE_DW, PCI_*, and PCIE_* as below.

1. Common Frameworks:
    These options are used by other controller drivers.
    e.g., PCIE_DW, PCIE_DW_HOST, PCIE_DW_EP.

2. PCI_* controller drivers:
    PCI_* was used earlier than PCIE_*. If a chip vendor's controllers provide
    both conventional PCI and PCI Express, or only conventional PCI, PCI_* can
    be used. For example, the reason PCI_EXYNOS was chosen instead of
    PCIE_EXYNOS, is that EXYNOS had controllers to support either conventional
    PCI or PCI Express.

3. PCIE_* controller drivers
    If a controller can support only PCI Express, not conventional PCI,
    PCIE_* is the proper naming.

Then, within PCI_* or PCIE_* categories, each controller option should be
in an alphabetical order for the readability. Also, other person or I will
send a patch to fix orders. (e.g., PCIE_QCOM, PCIE_AL, etc.)

>> Put PCIE_INTEL_GW between PCIE_ARTPEC6_EP and PCIE_KIRIN.
>
>Ok. I will update in the next patch version.

Ok, thank you.

Best regards,
Jingoo Han