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

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Date:   Fri, 23 Sep 2022 17:16:38 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Matthew Gerlach <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 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.

> +		switch (v) {
> +		case 0:
> +			break;
> +
> +		case 1:
> +			v =  readq(base + DFHv1_CSR_SIZE_GRP);

Extra space.

> +			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.

> +					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;
> +
> +		default:
> +			dev_warn(binfo->dev, "unexpected DFH version %lld\n", v);
> +			break;
> +		}
> +	}
> +
>  	if (!inr) {
>  		*irq_base = 0;
>  		*nr_irqs = 0;

-- 
 i.