Re: [PATCH v2 2/5] PCI: dwc: Check alloc_page() return value

From: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
To: Marc Zyngier <maz@misterjones.org>
Cc: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	linux-pci@vger.kernel.org,
	Binghui Wang <wangbinghui@hisilicon.com>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	linux-arm-kernel@axis.com, Jonathan Hunter <jonathanh@nvidia.com>,
	Fabio Estevam <festevam@gmail.com>,
	Jerome Brunet <jbrunet@baylibre.com>,
	Rob Herring <robh@kernel.org>,
	Jesper Nilsson <jesper.nilsson@axis.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Kevin Hilman <khilman@baylibre.com>,
	Pratyush Anand <pratyush.anand@gmail.com>,
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	Stanimir Varbanov <svarbanov@mm-sol.com>,
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	Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
	Shawn Guo <shawnguo@kernel.org>,
	Lucas Stach <l.stach@pengutronix.de>
Subject: Re: [PATCH v2 2/5] PCI: dwc: Check alloc_page() return value
Date: Wed, 30 Sep 2020 09:23:13 +0800	[thread overview]
Message-ID: <20200930092313.6124a082@xhacker.debian> (raw)
In-Reply-To: <74af578c79bd09f2111e5438917f2c6e@misterjones.org>

Hi Marc,

On Tue, 29 Sep 2020 18:29:52 +0100 Marc Zyngier wrote:

> 
> 
> On 2020-09-24 12:06, Jisheng Zhang wrote:
> > We need to check alloc_page() succeed or not before continuing.
> >
> > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
> > b/drivers/pci/controller/dwc/pcie-designware-host.c
> > index 0a19de946351..9e04e8ef3aa4 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > @@ -303,6 +303,11 @@ void dw_pcie_msi_init(struct pcie_port *pp)
> >       u64 msi_target;
> >
> >       pp->msi_page = alloc_page(GFP_KERNEL);
> > +     if (!pp->msi_page) {
> > +             dev_err(dev, "Failed to alloc MSI page\n");  
> 
> A failing allocation will already scream, so there is no need to
> add insult to injury.
> 
> More importantly, what is this MSI page ever used for? If I remember
> well, this is just a random address that never gets written to.
> 
> So why do we allocate a page here? Why do we bother with this DMA
> mapping?
> 

Ard and Rob also pointed out that there's no need to allocate a page, instead,
we could use an address in the driver data for MSI address. So I refactored
the patches and verified this solution works fine. Could you please review
the V5?

Thanks

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