linux-kernel - Re: [PATCH v1 2/7] fpga: dfl: check feature type before parse irq info

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Date:   Thu, 17 Feb 2022 10:38:16 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Tom Rix <trix@...hat.com>
Cc:     Tianfei zhang <tianfei.zhang@...el.com>, hao.wu@...el.com,
        mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        corbet@....net
Subject: Re: [PATCH v1 2/7] fpga: dfl: check feature type before parse irq
  info

On Tue, Feb 15, 2022 at 06:49:05AM -0800, Tom Rix wrote:
> 
> On 2/14/22 3:26 AM, Tianfei zhang wrote:
> > From: Tianfei Zhang <tianfei.zhang@...el.com>
> > 
> > The feature ID of "Port User Interrupt" and the
> > "PMCI Subsystem" are identical, 0x12, but one is for FME,
> > other is for Port. It should check the feature type While
> > parsing the irq info in parse_feature_irqs().
> 
> This seems like a bug fix and not part of iofs feature.
> 
> Split this out of the patchset.
> 
> This is a workaround a hardware problem, there should be some comments to
> the effect that you can't trust _this_ or _that_ feature id and some special
> handling earlier.
> 
> The ambiguity of feature id is a problem, and this sort of bug will happen

Actually this is not the feature id definition problem. The identity of the
feature is determined by the dfl_id_type(FME, PORT) AND feature_id. So the
driver should match the dfl_id_type & feature_id to know what feature it
is.

Thanks,
Yilun

> again.
> 
> What can be done to prevent this in the future ?
> 
> > 
> > Signed-off-by: Tianfei Zhang <tianfei.zhang@...el.com>
> > ---
> >   drivers/fpga/dfl.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> > index 599bb21d86af..26f8cf890700 100644
> > --- a/drivers/fpga/dfl.c
> > +++ b/drivers/fpga/dfl.c
> > @@ -940,9 +940,14 @@ static int parse_feature_irqs(struct build_feature_devs_info *binfo,
> >   {
> >   	void __iomem *base = binfo->ioaddr + ofst;
> >   	unsigned int i, ibase, inr = 0;
> > +	enum dfl_id_type type;
> >   	int virq;
> >   	u64 v;
> > +	type = feature_dev_id_type(binfo->feature_dev);
> > +	if (type >= DFL_ID_MAX)
> > +		return -EINVAL;
> > +
> >   	/*
> >   	 * Ideally DFL framework should only read info from DFL header, but
> >   	 * current version DFL only provides mmio resources information for
> > @@ -959,16 +964,22 @@ static int parse_feature_irqs(struct build_feature_devs_info *binfo,
> >   	 */
> >   	switch (fid) {
> >   	case PORT_FEATURE_ID_UINT:
> > +		if (type != PORT_ID)
> > +			break;
> 
> Instead of embedding a break in the switch, break the switch into fme switch
> and port switch
> 
> if (type == PORT_ID)
> 
>   port-switch
> 
> else if (type == FME_ID
> 
>   fme-switch
> 
> Tom
> 
> >   		v = readq(base + PORT_UINT_CAP);
> >   		ibase = FIELD_GET(PORT_UINT_CAP_FST_VECT, v);
> >   		inr = FIELD_GET(PORT_UINT_CAP_INT_NUM, v);
> >   		break;
> >   	case PORT_FEATURE_ID_ERROR:
> > +		if (type != PORT_ID)
> > +			break;
> >   		v = readq(base + PORT_ERROR_CAP);
> >   		ibase = FIELD_GET(PORT_ERROR_CAP_INT_VECT, v);
> >   		inr = FIELD_GET(PORT_ERROR_CAP_SUPP_INT, v);
> >   		break;
> >   	case FME_FEATURE_ID_GLOBAL_ERR:
> > +		if (type != FME_ID)
> > +			break;
> >   		v = readq(base + FME_ERROR_CAP);
> >   		ibase = FIELD_GET(FME_ERROR_CAP_INT_VECT, v);
> >   		inr = FIELD_GET(FME_ERROR_CAP_SUPP_INT, v);