linux-kernel - Re: [PATCH v1 1/3] PCI: dwc: refactor common code

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Message-ID: <20240304172809.GA31079@thinkpad>
Date: Mon, 4 Mar 2024 22:58:09 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Shashank Babu Chinta Venkata <quic_schintav@...cinc.com>,
	agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
	mani@...nel.org, quic_msarkar@...cinc.com,
	quic_kraravin@...cinc.com,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Serge Semin <fancer.lancer@...il.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Josh Triplett <josh@...htriplett.org>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v1 1/3] PCI: dwc: refactor common code

On Fri, Mar 01, 2024 at 01:44:56PM -0600, Bjorn Helgaas wrote:
> On Thu, Feb 29, 2024 at 09:11:34PM -0800, Shashank Babu Chinta Venkata wrote:
> > Refactor common code from RC(Root Complex) and EP(End Point)
> > drivers and move them to a common repository. This acts as placeholder
> > for common source code for both drivers avoiding duplication.
> > 
> > Signed-off-by: Shashank Babu Chinta Venkata <quic_schintav@...cinc.com>
> > ---
> >  drivers/pci/controller/dwc/Kconfig         |  5 ++
> >  drivers/pci/controller/dwc/Makefile        |  1 +
> >  drivers/pci/controller/dwc/pcie-qcom-cmn.c | 85 ++++++++++++++++++++++
> >  drivers/pci/controller/dwc/pcie-qcom-cmn.h | 30 ++++++++
> >  drivers/pci/controller/dwc/pcie-qcom-ep.c  | 39 +---------
> >  drivers/pci/controller/dwc/pcie-qcom.c     | 67 ++---------------
> >  6 files changed, 133 insertions(+), 94 deletions(-)
> >  create mode 100644 drivers/pci/controller/dwc/pcie-qcom-cmn.c
> >  create mode 100644 drivers/pci/controller/dwc/pcie-qcom-cmn.h
> 
> Hmm.  I'm a little ambivalent about adding two new files.  Overall I
> think I prefer the drivers that include both RC and EP mode in a
> single source file because one file is easier to browse than four and
> more things can be static.
> 
> A single file would also reduce quite a bit more duplication between
> pcie-qcom.c and pcie-qcom-ep.c, e.g., register names and fields with
> needlessly different names:
> 
>   #define AUX_PWR_DET                     BIT(4)  # pcie-qcom.c
>   #define PARF_SYS_CTRL_AUX_PWR_DET       BIT(4)  # pcie-qcom-ep.c
> 
> I do see PCIE_QCOM is bool and PCIE_QCOM_EP is tristate, so that and
> other considerations might make a single source file impractical.
> 

Yeah, we explored that option while adding the EP driver and it didn't look
feasible.

- Mani

> > +++ b/drivers/pci/controller/dwc/Makefile
> > @@ -27,6 +27,7 @@ obj-$(CONFIG_PCIE_UNIPHIER) += pcie-uniphier.o
> >  obj-$(CONFIG_PCIE_UNIPHIER_EP) += pcie-uniphier-ep.o
> >  obj-$(CONFIG_PCIE_VISCONTI_HOST) += pcie-visconti.o
> >  obj-$(CONFIG_PCIE_RCAR_GEN4) += pcie-rcar-gen4.o
> > +obj-$(CONFIG_PCIE_QCOM_CMN) += pcie-qcom-cmn.o
> 
> If we have to have pcie-qcom-cmn.o, at least move this next to the
> existing lines:
> 
>   obj-$(CONFIG_PCIE_QCOM) += pcie-qcom.o
>   obj-$(CONFIG_PCIE_QCOM_EP) += pcie-qcom-ep.o
> 
> > +++ b/drivers/pci/controller/dwc/pcie-qcom-cmn.c
> > @@ -0,0 +1,85 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2014-2015, 2020 The Linux Foundation. All rights reserved.
> > + * Copyright 2015, 2021 Linaro Limited.
> > + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
> > + *
> 
> Spurious blank line.
> 
> > +int qcom_pcie_cmn_icc_get_resource(struct dw_pcie *pci, struct icc_path *icc_mem)
> 
> I don't see the value of adding "cmn" in the middle of the names.
> 
> > +{
> > +	int ret = 0;
> > +
> > +	if (IS_ERR(pci))
> > +		return PTR_ERR(pci);
> > +
> > +	icc_mem = devm_of_icc_get(pci->dev, "pcie-mem");
> > +	if (IS_ERR(icc_mem))
> > +		return PTR_ERR(icc_mem);
> > +
> > +	return ret;
> 
> No need for the "ret" variable since it's never assigned.  "return 0"
> here would be easier to read.
> 
> > +int qcom_pcie_cmn_icc_init(struct dw_pcie *pci, struct icc_path *icc_mem)
> > +{
> > +	int ret = 0;
> 
> Unnecessary initialization.
> 
> > +++ b/drivers/pci/controller/dwc/pcie-qcom-cmn.h
> > @@ -0,0 +1,30 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (c) 2014-2015, 2020 The Linux Foundation. All rights reserved.
> > + * Copyright 2015, 2021 Linaro Limited.
> > + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
> > + */
> > +
> > +#include <linux/pci.h>
> > +#include "../../pci.h"
> > +#include "pcie-designware.h"
> > +
> > +#ifdef CONFIG_PCIE_QCOM_CMN
> 
> Why the #ifdef wrapper?  And why do we need the stubs when
> CONFIG_PCIE_QCOM_CMN isn't defined?
> 
> > +#else
> > +static inline int qcom_pcie_cmn_icc_get_resource(struct dw_pcie *pci, struct icc_path *icc_mem)
> > +{
> > +	return 0;
> > +}

-- 
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