linux-kernel - Re: [PATCH v9 06/10] PCI: dwc: ep: Call dw_pcie_ep_init_registers() API directly from all glue drivers

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Date: Fri, 8 Mar 2024 15:19:47 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Niklas Cassel <cassel@...nel.org>
Cc: Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Marek Vasut <marek.vasut+renesas@...il.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Vidya Sagar <vidyas@...dia.com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	NXP Linux Team <linux-imx@....com>,
	Minghuan Lian <minghuan.Lian@....com>,
	Mingkai Hu <mingkai.hu@....com>, Roy Zang <roy.zang@....com>,
	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	Srikanth Thokala <srikanth.thokala@...el.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
	linux-arm-kernel@...s.com
Subject: Re: [PATCH v9 06/10] PCI: dwc: ep: Call dw_pcie_ep_init_registers()
 API directly from all glue drivers

On Fri, Mar 08, 2024 at 10:05:11AM +0100, Niklas Cassel wrote:
> On Fri, Mar 08, 2024 at 11:06:24AM +0530, Manivannan Sadhasivam wrote:
> > On Thu, Mar 07, 2024 at 09:36:56PM +0100, Niklas Cassel wrote:
> > > On Mon, Mar 04, 2024 at 02:52:18PM +0530, Manivannan Sadhasivam wrote:
> > > > Currently, dw_pcie_ep_init_registers() API is directly called by the glue
> > > > drivers requiring active refclk from host. But for the other drivers, it is
> > > > getting called implicitly by dw_pcie_ep_init(). This is due to the fact
> > > > that this API initializes DWC EP specific registers and that requires an
> > > > active refclk (either from host or generated locally by endpoint itsef).
> > > > 
> > > > But, this causes a discrepancy among the glue drivers. So to avoid this
> > > > confusion, let's call this API directly from all glue drivers irrespective
> > > > of refclk dependency. Only difference here is that the drivers requiring
> > > > refclk from host will call this API only after the refclk is received and
> > > > other drivers without refclk dependency will call this API right after
> > > > dw_pcie_ep_init().
> > > > 
> > > > With this change, the check for 'core_init_notifier' flag can now be
> > > > dropped from dw_pcie_ep_init() API. This will also allow us to remove the
> > > > 'core_init_notifier' flag completely in the later commits.
> > > > 
> > > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > > ---
> > > >  drivers/pci/controller/dwc/pci-dra7xx.c           |  7 +++++++
> > > >  drivers/pci/controller/dwc/pci-imx6.c             |  8 ++++++++
> > > >  drivers/pci/controller/dwc/pci-keystone.c         |  9 +++++++++
> > > >  drivers/pci/controller/dwc/pci-layerscape-ep.c    |  7 +++++++
> > > >  drivers/pci/controller/dwc/pcie-artpec6.c         | 13 ++++++++++++-
> > > >  drivers/pci/controller/dwc/pcie-designware-ep.c   | 22 ----------------------
> > > >  drivers/pci/controller/dwc/pcie-designware-plat.c |  9 +++++++++
> > > >  drivers/pci/controller/dwc/pcie-keembay.c         | 16 +++++++++++++++-
> > > >  drivers/pci/controller/dwc/pcie-rcar-gen4.c       | 12 +++++++++++-
> > > >  drivers/pci/controller/dwc/pcie-uniphier-ep.c     | 13 ++++++++++++-
> > > >  10 files changed, 90 insertions(+), 26 deletions(-)
> > > > 
> > > > diff --git a/drivers/pci/controller/dwc/pci-dra7xx.c b/drivers/pci/controller/dwc/pci-dra7xx.c
> > > > index 0e406677060d..395042b29ffc 100644
> > > > --- a/drivers/pci/controller/dwc/pci-dra7xx.c
> > > > +++ b/drivers/pci/controller/dwc/pci-dra7xx.c
> > > > @@ -467,6 +467,13 @@ static int dra7xx_add_pcie_ep(struct dra7xx_pcie *dra7xx,
> > > >  		return ret;
> > > >  	}
> > > >  
> > > > +	ret = dw_pcie_ep_init_registers(ep);
> > > > +	if (ret) {
> > > 
> > > Here you are using if (ret) to error check the return from
> > > dw_pcie_ep_init_registers().
> > > 
> > > 
> > > > index c0c62533a3f1..8392894ed286 100644
> > > > --- a/drivers/pci/controller/dwc/pci-keystone.c
> > > > +++ b/drivers/pci/controller/dwc/pci-keystone.c
> > > > @@ -1286,6 +1286,13 @@ static int ks_pcie_probe(struct platform_device *pdev)
> > > >  		ret = dw_pcie_ep_init(&pci->ep);
> > > >  		if (ret < 0)
> > > >  			goto err_get_sync;
> > > > +
> > > > +		ret = dw_pcie_ep_init_registers(&pci->ep);
> > > > +		if (ret < 0) {
> > > 
> > > Here you are using if (ret < 0) to error check the return from
> > > dw_pcie_ep_init_registers(). Please be consistent.
> > > 
> > 
> > I maintained the consistency w.r.t individual drivers. Please check them
> > individually.
> > 
> > If I maintain consistency w.r.t this patch, then the style will change within
> > the drivers.
> 
> Personally, I disagree with that.
> 
> All glue drivers should use the same way of checking dw_pcie_ep_init(),
> depending on the kdoc of dw_pcie_ep_init().
> 
> If the kdoc for dw_pcie_ep_init() says returns 0 on success,
> then I think that it is strictly more correct to do:
> 
> ret = dw_pcie_ep_init()
> if (ret) {
> 	<error handling>
> }
> 
> And if a glue driver doesn't look like that, then I think we should change
> them. (Same reasoning for dw_pcie_ep_init_registers().)
> 
> 
> If you read code that looks like:
> ret = dw_pcie_ep_init()
> if (ret < 0) {
> 	<error handling>
> }
> 
> then you assume that is is a function with a kdoc that says it can return 0
> or a positive value on success, e.g. a function that returns an index in an
> array.
> 

But if you read the same function from the individual drivers, it could present
a different opinion because the samantics is different than others.

I'm not opposed to keeping the API semantics consistent, but we have to take
account of the drivers style as well.

- Mani

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