linux-kernel - Re: [PATCH v2 2/6] PCI: brcmstb: Split brcm_pcie

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Message-ID: <20220718224033.GA1450714@bhelgaas>
Date:   Mon, 18 Jul 2022 17:40:33 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jim Quinlan <jim2101024@...il.com>
Cc:     linux-pci@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Cyril Brulebois <kibi@...ian.org>,
        bcm-kernel-feedback-list@...adcom.com, james.quinlan@...adcom.com,
        Florian Fainelli <f.fainelli@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/6] PCI: brcmstb: Split brcm_pcie_setup() into two
 funcs

On Mon, Jul 18, 2022 at 01:14:25PM -0500, Bjorn Helgaas wrote:
> ...

> So I think brcm_pcie_setup() does initialization that doesn't depend
> on the link or any downstream devices, and brcm_pcie_start_link() does
> things that depend on the link being up.  Right?
> 
> If so, "start_link" might be a slight misnomer since AFAICT
> brcm_pcie_start_link() doesn't do anything to initiate link-up except
> maybe deasserting fundamental reset.  Some drivers start the LTSSM or
> explicitly enable link training, but brcm_pcie_start_link() doesn't
> seem to do anything like that.
> 
> brcm_pcie_start_link() still does brcm_pcie_set_outbound_win().  Does
> that really depend on the link being up?  If that only affects the
> Root Port, maybe it could be done before link-up?

What about the /* PCIe->SCB endian mode for BAR */ thing?  Does that
depend on the link being up?

And the "Refclk from RC should be gated with CLKREQ#" part?  Does that
depend on the link being up?

It seems obvious that brcm_pcie_set_ssc() and reading the negotiated
link speed and width depend on the link being up.