RE: [PATCH v1 2/7] fpga: dfl: check feature type before parse irq info

Zhang, Tianfei
2022-02-18T06:53:17Z

> -----Original Message-----
> From: Tom Rix <trix@redhat.com>
> Sent: Tuesday, February 15, 2022 10:49 PM
> To: Zhang, Tianfei <tianfei.zhang@intel.com>; Wu, Hao <hao.wu@intel.com>;
> mdf@kernel.org; Xu, Yilun <yilun.xu@intel.com>; linux-fpga@vger.kernel.org;
> linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: corbet@lwn.net
> Subject: Re: [PATCH v1 2/7] fpga: dfl: check feature type before parse irq info
>
>
> On 2/14/22 3:26 AM, Tianfei zhang wrote:
> > From: Tianfei Zhang <tianfei.zhang@intel.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 again.
>
> What can be done to prevent this in the future ?

This patch is not workaround, this is a bug fix for DFL driver.
The root cause is that DLF driver miss check the feature type while parsing the interrupt information,
because some Feature IDs are identical between FME and Port, like PMCI in FME and "Port User Interrupt"
in Port.
The definition of Feature ID is here:
https://github.com/OPAE/linux-dfl-feature-id/blob/master/dfl-feature-ids.rst

>
> >
> > Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.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

Your suggestion is looks good for me, I will change on next version.

>
> 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);