linux-kernel - Re: [PATCH v2 4/6] fpga: dfl: add generic support for MSIX interrupts

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Date:   Tue, 27 Sep 2022 09:46:32 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     matthew.gerlach@...ux.intel.com
cc:     hao.wu@...el.com, yilun.xu@...el.com, russell.h.weight@...el.com,
        basheer.ahmed.muddebihal@...el.com, trix@...hat.com,
        mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        tianfei.zhang@...el.com, corbet@....net,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        Jiri Slaby <jirislaby@...nel.org>, geert+renesas@...der.be,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        niklas.soderlund+renesas@...natech.se, phil.edworthy@...esas.com,
        macro@...am.me.uk, johan@...nel.org, Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v2 4/6] fpga: dfl: add generic support for MSIX
 interrupts

On Mon, 26 Sep 2022, matthew.gerlach@...ux.intel.com wrote:

> 
> 
> On Fri, 23 Sep 2022, Ilpo Järvinen wrote:
> 
> > On Fri, 23 Sep 2022, matthew.gerlach@...ux.intel.com wrote:
> > 
> > > From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> > > 
> > > Define and use a DFHv1 parameter to add generic support for MSIX
> > > interrupts for DFL devices.
> > > 
> > > Signed-off-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> > > ---
> > > v2: fix kernel doc
> > >     clarify use of DFH_VERSION field
> > > ---
> > >  drivers/fpga/dfl.c  | 60 +++++++++++++++++++++++++++++++++++++++++----
> > >  include/linux/dfl.h | 14 +++++++++++
> > >  2 files changed, 69 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> > > index 1132f3c10440..dfd3f563c92d 100644
> > > --- a/drivers/fpga/dfl.c
> > > +++ b/drivers/fpga/dfl.c
> > > @@ -941,23 +941,22 @@ 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;
> > > +	int virq, off;
> > >  	u64 v;
> > > 
> > >  	type = feature_dev_id_type(binfo->feature_dev);
> > > 
> > >  	/*
> > >  	 * Ideally DFL framework should only read info from DFL header, but
> > > -	 * current version DFL only provides mmio resources information for
> > > +	 * current version, DFHv0, only provides mmio resources information
> > > for
> > >  	 * each feature in DFL Header, no field for interrupt resources.
> > >  	 * Interrupt resource information is provided by specific mmio
> > >  	 * registers of each private feature which supports interrupt. So in
> > >  	 * order to parse and assign irq resources, DFL framework has to look
> > >  	 * into specific capability registers of these private features.
> > >  	 *
> > > -	 * Once future DFL version supports generic interrupt resource
> > > -	 * information in common DFL headers, the generic interrupt parsing
> > > -	 * code will be added. But in order to be compatible to old version
> > > +	 * DFHv1 supports generic interrupt resource information in DFHv1
> > > +	 * parameter blocks. But in order to be compatible to old version
> > >  	 * DFL, the driver may still fall back to these quirks.
> > >  	 */
> > >  	if (type == PORT_ID) {
> > > @@ -981,6 +980,36 @@ static int parse_feature_irqs(struct
> > > build_feature_devs_info *binfo,
> > >  		}
> > >  	}
> > > 
> > > +	if (fid != FEATURE_ID_AFU && fid != PORT_FEATURE_ID_ERROR &&
> > > +	    fid != PORT_FEATURE_ID_UINT && fid != FME_FEATURE_ID_GLOBAL_ERR) {
> > > +
> > > +		v = FIELD_GET(DFH_VERSION, readq(base));
> > 
> > I'd call this variable version (or ver) if you want to store it but it
> > would also fit to switch () line so that no extra variable is needed.
> 
> I will change the v to dfh_ver to be clearer.  I want to store the value
> because it is used in the default case in the error message.  The error
> message helps to debug broken FPGA images.

Right, I missed that (or didn't think it too much and all being called 
"v" didn't help either :-)).

> > > +			if (FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS, v)) {
> > > +				off = dfl_find_param(base + DFHv1_PARAM_HDR,
> > > ofst,
> > > +						     DFHv1_PARAM_ID_MSIX);
> > > +				if (off >= 0) {
> > 
> > I'd reverse these 2 conditions and break when there's nothing to do.
> 
> I'm not sure what you mean by reversing these conditions because a DFHv1 may
> or may not have parameters (the first condition), and a DFHv1 may have
> parameters but may not have a MSI-X parameter (the second condition).

This is what I meant:

		if (!FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS, v))
			break;

		off = dfl_find_param(...);
		if (off < 0)
			break;

		ibase = ...


-- 
 i.


> > > +					ibase = readl(base + DFHv1_PARAM_HDR +
> > > +						      off +
> > > DFHv1_PARAM_MSIX_STARTV);
> > > +					inr = readl(base + DFHv1_PARAM_HDR +
> > > +						    off +
> > > DFHv1_PARAM_MSIX_NUMV);
> > > +					dev_dbg(binfo->dev, "start %d num %d
> > > fid 0x%x\n",
> > > +						ibase, inr, fid);
> > > +				}
> > > +			}
> > > +			break;