linux-kernel - Re: [RFC PATCH v2 1/4] PCI: pcie-rockchip: add Link Control and Status Register 2

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Message-ID: <aEoj385BMtLvNuKL@geday>
Date: Wed, 11 Jun 2025 21:48:31 -0300
From: Geraldo Nascimento <geraldogabriel@...il.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-rockchip@...ts.infradead.org,
	Shawn Lin <shawn.lin@...k-chips.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Heiko Stuebner <heiko@...ech.de>, Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	linux-phy@...ts.infradead.org, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/4] PCI: pcie-rockchip: add Link Control and
 Status Register 2

On Wed, Jun 11, 2025 at 02:42:59PM -0500, Bjorn Helgaas wrote:
> On Tue, Jun 10, 2025 at 06:19:49PM -0300, Geraldo Nascimento wrote:
> > +#define PCIE_RC_CONFIG_DCR		(PCIE_RC_CONFIG_CR + PCI_EXP_DEVCAP)
> 
> I would really like to see PCI_EXP_DEVCAP referenced in the source
> where we currently use PCIE_RC_CONFIG_DCR.  That way, cscope/tags/grep
> will find the actual uses of PCI_EXP_DEVCAP, not just this #define of
> PCIE_RC_CONFIG_DCR.
> 
> Something like this:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pci-mvebu.c?id=v6.15#n265
>

Hi Bjorn,

Yes, thank you for the code snippet, it makes things more clear.

> >  #define   PCIE_RC_CONFIG_DCR_CSPL_SHIFT		18
> >  #define   PCIE_RC_CONFIG_DCR_CSPL_LIMIT		0xff
> >  #define   PCIE_RC_CONFIG_DCR_CPLS_SHIFT		26
> 
> Also use PCI_EXP_DEVCAP_PWR_VAL and PCI_EXP_DEVCAP_PWR_SCL here if
> possible.  And FIELD_GET()/FIELD_PREP(), which avoid the need to
> define _SHIFT values.
> 
> I would do a pure conversion patch of the existing #defines.  Then I
> suspect you wouldn't need a patch to add the Link 2 registers at all
> because you could just use the #defines from pci_regs.h.
>

Got it!

Thanks!
Geraldo Nascimento