linux-kernel - Re: [PATCH RESEND v4 04/15] PCI: dwc: Add IP-core version detection procedure

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Date:   Mon, 1 Aug 2022 15:06:06 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>, Rob Herring <robh+dt@...nel.org>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v4 04/15] PCI: dwc: Add IP-core version detection
 procedure

On Mon, Aug 01, 2022 at 06:42:19PM +0530, Manivannan Sadhasivam wrote:
> On Fri, Jun 24, 2022 at 05:39:36PM +0300, Serge Semin wrote:
> > Since DWC PCIe v4.70a the controller version and version type can be read
> > from the PORT_LOGIC.PCIE_VERSION_OFF and PORT_LOGIC.PCIE_VERSION_TYPE_OFF
> > registers respectively. Seeing the generic code has got version-dependent
> > parts let's use these registers to find out the controller version.  The
> > detection procedure is executed for both RC and EP modes right after the
> > platform-specific initialization. We can't do that earlier since the
> > glue-drivers can perform the DBI-related setups there including the bus
> > reference clocks activation, without which the CSRs just can't be read.
> > 
> > Note the CSRs content is zero on the older DWC PCIe controller. In that
> > case we have no choice but to rely on the platform setup.
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> 
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> 
> > Reviewed-by: Rob Herring <robh@...nel.org>

> > @@ -711,6 +711,8 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> >  	ep->phys_base = res->start;
> >  	ep->addr_size = resource_size(res);
> >  
> > +	dw_pcie_version_detect(pci);
> > +
> 
> There is still an ongoing debate about moving all DBI accesses to
> init_complete. But this is fine atm.

Well, if I understand it correctly, e966f7390da9 ("PCI: dwc: Refactor
core initialization code for EP mode") claims that all DBI accesses
should be in dw_pcie_ep_init_complete(), so it's not so much a debate
as a discussion about how best to achieve that.

But you're right, we can fix that up later if necessary.

> >  	dw_pcie_iatu_detect(pci);