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

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Message-ID: <20220802073133.GB2494@thinkpad>
Date:   Tue, 2 Aug 2022 13:01:33 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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>,
        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 03:06:06PM -0500, Bjorn Helgaas wrote:
> 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.
> 

Glad to know that we are on the same page. Let's continue the discussion in
that thread.

Thanks,
Mani

> But you're right, we can fix that up later if necessary.
> 
> > >  	dw_pcie_iatu_detect(pci);

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