linux-kernel - Re: [PATCH RESEND v4 03/15] PCI: dwc: Convert to using native IP-core versions representation

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Message-ID: <20220728185311.3b4n2izy64fdpfk6@mobilestation>
Date:   Thu, 28 Jul 2022 21:53:11 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rahul Tanwar <rtanwar@...linear.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH RESEND v4 03/15] PCI: dwc: Convert to using native
 IP-core versions representation

On Thu, Jul 28, 2022 at 10:24:18AM -0500, Bjorn Helgaas wrote:
> On Fri, Jun 24, 2022 at 05:39:35PM +0300, Serge Semin wrote:
> > Since DWC PCIe v4.70a the controller version can be read from the
> > PORT_LOGIC.PCIE_VERSION_OFF register. Version is represented in the FourCC
> > format [1]. It's standard versioning approach for the Synopsys DWC
> > IP-cores. Moreover some of the DWC kernel drivers already make use of it
> > to fixup version-dependent functionality (See DWC USB3, Stmicro STMMAC or
> > recent DW SPI driver).
> 

> These references to other drivers might be useful, but without a
> function name or file name, I can't easily find them.

1. DW APB SSI driver, defined in drivers/spi/spi-dw.h:
#define DW_HSSI_102A                    0x3130322a
#define dw_spi_ip_is(_dws, _ip) ...
#define dw_spi_ver_is(_dws, _ip, _ver) ...
#define dw_spi_ver_is_ge(_dws, _ip, _ver) ...

2. DWC USB3 driver, defined in drivers/usb/dwc3/core.h
#define DWC3_IP                 0x5533
#define DWC31_IP                0x3331
#define DWC32_IP                0x3332
#define DWC3_REVISION_173A      0x5533173a
#define DWC3_REVISION_175A      0x5533175a
...
#define DWC31_REVISION_110A     0x3131302a
#define DWC31_REVISION_120A     0x3132302a
...
#define DWC3_IP_IS(_ip) ...
#define DWC3_VER_IS(_ip, _ver) ...
#define DWC3_VER_IS_PRIOR(_ip, _ver) ...
#define DWC3_VER_IS_WITHIN(_ip, _from, _to) ...
#define DWC3_VER_TYPE_IS_WITHIN(_ip, _ver, _from, _to) ...

Regarding the STMMAC (DW MAC/GMAC/xGMAC) driver. I've harried up to
claim it has the native IP-core versioning support. The current kernel
driver doesn't have it. Instead I have it implemented in my local
repo, but it isn't ready to be submitted yet. I need some more time to
finish my DW GMAC/xGMAC work first.

Ideally we could have created a common interface for all the drivers.
I thought about it first when I was initially creating the patchsets.
But now I don't time left for this at all. The review process's taken
way much more time than I had/planned to spend for the PCIe-patches.
So what I can do at this stage is to provide minor fixes if required.

-Sergey

> 
> > In order to preserve the standard version
> > representation and prevent the data conversion back and forth, we suggest
> > to preserve the native version representation in the DWC PCIe driver too
> > in the same way as it has already been done in the rest of the DWC
> > drivers. IP-core version reading from the CSR will be introduced in the
> > next commit together with a simple macro-based API to use it.
> > 
> > [1] https://en.wikipedia.org/wiki/FourCC