linux-kernel - Re: [PATCH] PCI: mediatek: Verify whether the free

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Date:   Fri, 30 Apr 2021 12:13:20 +0530
From:   Amey Narkhede <ameynarkhede03@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Ryder Lee <ryder.lee@...iatek.com>, lorenzo.pieralisi@....com,
        Rob Herring <robh@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] PCI: mediatek: Verify whether the free_ck clock is
 ungated or not

On 21/04/29 05:38PM, Bjorn Helgaas wrote:
> Can you make the subject say something at a higher level instead of
> just paraphrasing the C code?  I'm guessing this means resume will now
> fail if the clock isn't turned on?
>
> On Thu, Apr 29, 2021 at 07:17:49PM +0530, Amey Narkhede wrote:
> > Verify that the free_ck clock is ungated on device resume
> > by checking return value of clk_prepare_enable().
>
> Also the commit log -- this doesn't say anything more than the code
> itself.  Did you find this by tripping over it?  Or just by code
> inspection?  I guess without the check, we continue on and try to
> resume, but accesses to PCI devices fail and maybe return ~0 data or
> cause machine checks or something?
>
I found this with code inspection. Sorry for the unclear commit
messsage. I'll try to clarify it in v2.
> > Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
> > ---
> >  drivers/pci/controller/pcie-mediatek.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
> > index 23548b517..9b13214bf 100644
> > --- a/drivers/pci/controller/pcie-mediatek.c
> > +++ b/drivers/pci/controller/pcie-mediatek.c
> > @@ -1154,11 +1154,14 @@ static int __maybe_unused mtk_pcie_resume_noirq(struct device *dev)
> >  {
> >  	struct mtk_pcie *pcie = dev_get_drvdata(dev);
> >  	struct mtk_pcie_port *port, *tmp;
> > +	int ret;
> >
> >  	if (list_empty(&pcie->ports))
> >  		return 0;
> >
> > -	clk_prepare_enable(pcie->free_ck);
> > +	ret = clk_prepare_enable(pcie->free_ck);
> > +	if (ret)
> > +		return ret;
>
> Most callers print an error message when clk_prepare_enable() fails.
>
[...]
I'll update this in v2.

Thanks,
Amey