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

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Date:   Tue, 27 Sep 2022 05:17:14 -0700 (PDT)
From:   matthew.gerlach@...ux.intel.com
To:     Ilpo Järvinen <ilpo.jarvinen@...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 Tue, 27 Sep 2022, Ilpo Järvinen wrote:

> 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 understand now.  This is a good suggestion because the resulting 
indentation is better.

Thanks,
Matthew


>
>
> -- 
> 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;
>