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Date:   Tue, 11 Oct 2022 14:28:03 +0800
From:   Xu Yilun <yilun.xu@intel.com>
To:     matthew.gerlach@linux.intel.com
Cc:     hao.wu@intel.com, russell.h.weight@intel.com,
        basheer.ahmed.muddebihal@intel.com, trix@redhat.com,
        mdf@kernel.org, linux-fpga@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        tianfei.zhang@intel.com, corbet@lwn.net,
        gregkh@linuxfoundation.org, linux-serial@vger.kernel.org,
        jirislaby@kernel.org, geert+renesas@glider.be,
        andriy.shevchenko@linux.intel.com,
        niklas.soderlund+renesas@ragnatech.se, macro@orcam.me.uk,
        johan@kernel.org, lukas@wunner.de
Subject: Re: [PATCH v3 3/4] fpga: dfl: add basic support for DFHv1
Message-ID: <Y0UM87Tkq0VfBVJn@yilunxu-OptiPlex-7050>
References: <20221004143718.1076710-1-matthew.gerlach@linux.intel.com>
 <20221004143718.1076710-4-matthew.gerlach@linux.intel.com>
 <Yz6ffEeKZButHw4m@yilunxu-OptiPlex-7050>
 <alpine.DEB.2.22.394.2210100937280.2404672@rhweight-WRK1>
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On 2022-10-10 at 09:58:00 -0700, matthew.gerlach@linux.intel.com wrote:
> 
> 
> On Thu, 6 Oct 2022, Xu Yilun wrote:
> 
> > On 2022-10-04 at 07:37:17 -0700, matthew.gerlach@linux.intel.com wrote:
> > > From: Matthew Gerlach <matthew.gerlach@linux.intel.com>
> > > 
> > > Add generic support for MSIX interrupts for DFL devices.
> > > 
> > > The location of a feature's registers is explicitly
> > > described in DFHv1 and can be relative to the base of the DFHv1
> > > or an absolute address.  Parse the location and pass the information
> > > to DFL driver.
> > > 
> > > Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
> > > ---
> > > v3: remove unneeded blank line
> > >     use clearer variable name
> > >     pass finfo into parse_feature_irqs()
> > >     refactor code for better indentation
> > >     use switch statement for irq parsing
> > >     squash in code parsing register location
> > > 
> > > v2: fix kernel doc
> > >     clarify use of DFH_VERSION field
> > > ---
> > >  drivers/fpga/dfl.c  | 150 ++++++++++++++++++++++++++++++++------------
> > >  drivers/fpga/dfl.h  |   3 +
> > >  include/linux/dfl.h |  20 ++++++
> > >  3 files changed, 134 insertions(+), 39 deletions(-)
> > > 
> > > diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> > > index b9aae85ba930..6a74317e549e 100644
> > > --- a/drivers/fpga/dfl.c
> > > +++ b/drivers/fpga/dfl.c
> > > @@ -380,7 +380,11 @@ dfl_dev_add(struct dfl_feature_platform_data *pdata,
> > >  	ddev->type = feature_dev_id_type(pdev);
> > >  	ddev->feature_id = feature->id;
> > >  	ddev->revision = feature->revision;
> > > +	ddev->dfh_version = feature->dfh_version;
> > >  	ddev->cdev = pdata->dfl_cdev;
> > > +	ddev->csr_res.start = feature->csr_res.start;
> > > +	ddev->csr_res.end = feature->csr_res.end;
> > > +	ddev->csr_res.flags = IORESOURCE_MEM;
> > > 
> > >  	/* add mmio resource */
> > >  	parent_res = &pdev->resource[feature->resource_index];
> > > @@ -708,18 +712,24 @@ struct build_feature_devs_info {
> > >   * struct dfl_feature_info - sub feature info collected during feature dev build
> > >   *
> > >   * @fid: id of this sub feature.
> > > + * @revision: revision of this sub feature
> > > + * @dfh_version: version of Device Feature Header (DFH)
> > >   * @mmio_res: mmio resource of this sub feature.
> > >   * @ioaddr: mapped base address of mmio resource.
> > >   * @node: node in sub_features linked list.
> > > + * @csr_res: resource of DFHv1 feature registers
> > > + * @csr_size: DFHv1 size of feature registers
> > >   * @irq_base: start of irq index in this sub feature.
> > >   * @nr_irqs: number of irqs of this sub feature.
> > >   */
> > >  struct dfl_feature_info {
> > >  	u16 fid;
> > >  	u8 revision;
> > > +	u8 dfh_version;
> > >  	struct resource mmio_res;
> > >  	void __iomem *ioaddr;
> > >  	struct list_head node;
> > > +	struct resource csr_res;
> > >  	unsigned int irq_base;
> > >  	unsigned int nr_irqs;
> > >  };
> > > @@ -797,6 +807,9 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
> > >  		feature->dev = fdev;
> > >  		feature->id = finfo->fid;
> > >  		feature->revision = finfo->revision;
> > > +		feature->dfh_version = finfo->dfh_version;
> > > +		feature->csr_res.start = finfo->csr_res.start;
> > > +		feature->csr_res.end = finfo->csr_res.end;
> > > 
> > >  		/*
> > >  		 * the FIU header feature has some fundamental functions (sriov
> > > @@ -935,55 +948,74 @@ static u16 feature_id(u64 value)
> > >  }
> > > 
> > >  static int parse_feature_irqs(struct build_feature_devs_info *binfo,
> > > -			      resource_size_t ofst, u16 fid,
> > > -			      unsigned int *irq_base, unsigned int *nr_irqs)
> > > +			      resource_size_t ofst, struct dfl_feature_info *finfo)
> > >  {
> > >  	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);
> > > +	u16 fid = finfo->fid;
> > > +	u64 v, dfh_ver;
> > > +	int virq, off;
> > > 
> > >  	/*
> > >  	 * 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) {
> > > -		switch (fid) {
> > > -		case PORT_FEATURE_ID_UINT:
> > > -			v = readq(base + PORT_UINT_CAP);
> > > -			ibase = FIELD_GET(PORT_UINT_CAP_FST_VECT, v);
> > > -			inr = FIELD_GET(PORT_UINT_CAP_INT_NUM, v);
> > > +
> > > +	switch (finfo->dfh_version) {
> > > +	case 0:
> > > +		type = feature_dev_id_type(binfo->feature_dev);
> > > +		if (type == PORT_ID) {
> > > +			switch (fid) {
> > > +			case PORT_FEATURE_ID_UINT:
> > > +				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:
> > > +				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;
> > > +			}
> > > +		} else if (type == FME_ID) {
> > > +			if (fid == FME_FEATURE_ID_GLOBAL_ERR) {
> > > +				v = readq(base + FME_ERROR_CAP);
> > > +				ibase = FIELD_GET(FME_ERROR_CAP_INT_VECT, v);
> > > +				inr = FIELD_GET(FME_ERROR_CAP_SUPP_INT, v);
> > > +			}
> > > +		}
> > > +		break;
> > > +
> > > +	case 1:
> > > +		if (!dfhv1_has_params(base))
> > >  			break;
> > > -		case PORT_FEATURE_ID_ERROR:
> > > -			v = readq(base + PORT_ERROR_CAP);
> > > -			ibase = FIELD_GET(PORT_ERROR_CAP_INT_VECT, v);
> > > -			inr = FIELD_GET(PORT_ERROR_CAP_SUPP_INT, v);
> > > +
> > > +		off = dfhv1_find_param(base, ofst, DFHv1_PARAM_ID_MSIX);
> > > +		if (off < 0)
> > >  			break;
> > > -		}
> > > -	} else if (type == FME_ID) {
> > > -		if (fid == FME_FEATURE_ID_GLOBAL_ERR) {
> > > -			v = readq(base + FME_ERROR_CAP);
> > > -			ibase = FIELD_GET(FME_ERROR_CAP_INT_VECT, v);
> > > -			inr = FIELD_GET(FME_ERROR_CAP_SUPP_INT, v);
> > > -		}
> > > +
> > > +		ibase = readl(base + off + DFHv1_PARAM_MSIX_STARTV);
> > > +		inr = readl(base + off + DFHv1_PARAM_MSIX_NUMV);
> > > +		break;
> > > +
> > > +	default:
> > > +		dev_warn(binfo->dev, "unexpected DFH version %lld\n", dfh_ver);
> > > +		break;
> > >  	}
> > > 
> > >  	if (!inr) {
> > > -		*irq_base = 0;
> > > -		*nr_irqs = 0;
> > > +		finfo->irq_base = 0;
> > > +		finfo->nr_irqs = 0;
> > >  		return 0;
> > >  	}
> > > 
> > > @@ -1006,8 +1038,8 @@ static int parse_feature_irqs(struct build_feature_devs_info *binfo,
> > >  		}
> > >  	}
> > > 
> > > -	*irq_base = ibase;
> > > -	*nr_irqs = inr;
> > > +	finfo->irq_base = ibase;
> > > +	finfo->nr_irqs = inr;
> > > 
> > >  	return 0;
> > >  }
> > > @@ -1023,8 +1055,8 @@ static int
> > >  create_feature_instance(struct build_feature_devs_info *binfo,
> > >  			resource_size_t ofst, resource_size_t size, u16 fid)
> > >  {
> > > -	unsigned int irq_base, nr_irqs;
> > >  	struct dfl_feature_info *finfo;
> > > +	u8 dfh_version = 0;
> > >  	u8 revision = 0;
> > >  	int ret;
> > >  	u64 v;
> > > @@ -1032,7 +1064,7 @@ create_feature_instance(struct build_feature_devs_info *binfo,
> > >  	if (fid != FEATURE_ID_AFU) {
> > >  		v = readq(binfo->ioaddr + ofst);
> > >  		revision = FIELD_GET(DFH_REVISION, v);
> > > -
> > > +		dfh_version = FIELD_GET(DFH_VERSION, v);
> > >  		/* read feature size and id if inputs are invalid */
> > >  		size = size ? size : feature_size(v);
> > >  		fid = fid ? fid : feature_id(v);
> > > @@ -1041,21 +1073,33 @@ create_feature_instance(struct build_feature_devs_info *binfo,
> > >  	if (binfo->len - ofst < size)
> > >  		return -EINVAL;
> > > 
> > > -	ret = parse_feature_irqs(binfo, ofst, fid, &irq_base, &nr_irqs);
> > > -	if (ret)
> > > -		return ret;
> > > -
> > >  	finfo = kzalloc(sizeof(*finfo), GFP_KERNEL);
> > >  	if (!finfo)
> > >  		return -ENOMEM;
> > > 
> > >  	finfo->fid = fid;
> > >  	finfo->revision = revision;
> > > +	finfo->dfh_version = dfh_version;
> > >  	finfo->mmio_res.start = binfo->start + ofst;
> > >  	finfo->mmio_res.end = finfo->mmio_res.start + size - 1;
> > >  	finfo->mmio_res.flags = IORESOURCE_MEM;
> > > -	finfo->irq_base = irq_base;
> > > -	finfo->nr_irqs = nr_irqs;
> > > +
> > > +	ret = parse_feature_irqs(binfo, ofst, finfo);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	if (dfh_version == 1) {
> > > +		v = readq(binfo->ioaddr + ofst + DFHv1_CSR_ADDR);
> > > +		if (v & DFHv1_CSR_ADDR_REL)
> > > +			finfo->csr_res.start = FIELD_GET(DFHv1_CSR_ADDR_MASK, v);
> > > +		else
> > > +			finfo->csr_res.start = binfo->start + ofst
> > > +					       + FIELD_GET(DFHv1_CSR_ADDR_MASK, v);
> > > +
> > > +		v = readq(binfo->ioaddr + ofst + DFHv1_CSR_SIZE_GRP);
> > > +		finfo->csr_res.end = finfo->csr_res.start
> > > +				     + FIELD_GET(DFHv1_CSR_SIZE_GRP_SIZE, v) - 1;
> > > +	}
> > > 
> > >  	list_add_tail(&finfo->node, &binfo->sub_features);
> > >  	binfo->feature_num++;
> > > @@ -1879,6 +1923,34 @@ long dfl_feature_ioctl_set_irq(struct platform_device *pdev,
> > >  }
> > >  EXPORT_SYMBOL_GPL(dfl_feature_ioctl_set_irq);
> > > 
> > > +int dfhv1_find_param(void __iomem *base, resource_size_t max, int param)
> > > +{
> > > +	int off = DFHv1_PARAM_HDR;
> > > +	u64 v, next;
> > > +
> > > +	while (off < max) {
> > > +		v = readq(base + off);
> > > +		if (param == FIELD_GET(DFHv1_PARAM_HDR_ID, v))
> > > +			return (DFHv1_PARAM_DATA + off);
> > > +
> > > +		next = FIELD_GET(DFHv1_PARAM_HDR_NEXT_OFFSET, v);
> > > +		if (!next)
> > > +			break;
> > > +
> > > +		off += next;
> > > +	}
> > > +
> > > +	return -ENOENT;
> > > +}
> > > +EXPORT_SYMBOL_GPL(dfhv1_find_param);
> > > +
> > > +int dfhv1_has_params(void __iomem *dfh_base)
> > > +{
> > > +	return (FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS,
> > > +		readq(dfh_base + DFHv1_CSR_SIZE_GRP)));
> > > +}
> > > +EXPORT_SYMBOL_GPL(dfhv1_has_params);
> > > +
> > >  static void __exit dfl_fpga_exit(void)
> > >  {
> > >  	dfl_chardev_uinit();
> > > diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
> > > index bd8720bc5320..0423aa8319ed 100644
> > > --- a/drivers/fpga/dfl.h
> > > +++ b/drivers/fpga/dfl.h
> > > @@ -266,6 +266,7 @@ struct dfl_feature_irq_ctx {
> > >   *		    this index is used to find its mmio resource from the
> > >   *		    feature dev (platform device)'s resources.
> > >   * @ioaddr: mapped mmio resource address.
> > > + * @csr_res: resource for DFHv1 feature registers
> > >   * @irq_ctx: interrupt context list.
> > >   * @nr_irqs: number of interrupt contexts.
> > >   * @ops: ops of this sub feature.
> > > @@ -276,8 +277,10 @@ struct dfl_feature {
> > >  	struct platform_device *dev;
> > >  	u16 id;
> > >  	u8 revision;
> > > +	u8 dfh_version;
> > >  	int resource_index;
> > >  	void __iomem *ioaddr;
> > > +	struct resource csr_res;
> > >  	struct dfl_feature_irq_ctx *irq_ctx;
> > >  	unsigned int nr_irqs;
> > >  	const struct dfl_feature_ops *ops;
> > > diff --git a/include/linux/dfl.h b/include/linux/dfl.h
> > > index 1a1a2b894687..71760c6a25d7 100644
> > > --- a/include/linux/dfl.h
> > > +++ b/include/linux/dfl.h
> > > @@ -39,6 +39,7 @@ enum dfl_id_type {
> > >   * @type: type of DFL FIU of the device. See enum dfl_id_type.
> > >   * @feature_id: feature identifier local to its DFL FIU type.
> > >   * @mmio_res: mmio resource of this dfl device.
> > > + * @csr_res: resource for DFHv1 feature registers
> > 
> > I think the combination of mmio_res & csr_res is confusing. Why a
> > special csr_res dedicated for DFHv1, and what the mmio_res stands for if
> > the csr_res exists? And they may overlap each other.
> 
> With DFHv1, the registers of a feature may be in a different location than
> the location of the Device Feature Header.  So a resource is needed for the
> DFH and another resource for the actual register space.  Would changing the
> name of mmio_res to dfh_res be less confusing? Unfortunately, changing the
> name of mmio_res would impact the existing dfl drivers.

There are 4 existing dfl drivers now, I think making changes is still
possible. But what is more important to me is to have a clear definition
of resource layout for dfl_device structure, cause it is used in other kernel
domains. Resource overlapping is hard to understand.

Some possible options in my mind:
1. keep the mmio_res, but it only includes the csr region.

   dfl driver couldn't access dfl header & param directly, but I think
   it's OK, dfl drivers don't have to care too much about the HW layout
   of dfl header & param. The header & param values could be parsed in dfl
   core and provided to dfl drivers by APIs.

   No extension of multiple csr regions in future.

2. struct resource mmio_res -> int num_mmio_res & struct resource *mmio_res

   Same as platform device, multiple resources for multiple memory blocks,
   maybe each tagged by name, they don't overlap each other. It impacts the
   existing dfl drivers, but may support multiple csr regions if possible.

> 
> The two resources may overlap, but that is why in
> drivers/tty/serial/8250/8250_dfl.c the mmio_res is mapped, then DFH parsed,
> and unmapped before the csr_res is mapped in the call to
> serial8250_register_8250_port().

This is what I want to avoid, every dfl driver needs the same routine
for the mmios they really want, which is a challenge to all domain
reviewers.

Thanks,
Yilun

> 
> > 
> > Could you present some general purpose mmio resource layout which is
> > compatible to dfl v0 & v1? People from other domains just need to know
> > the basic concept like how many register blocks in the device, what are
> > their ranges ...
> 
> I don't know how a single resource object can be used in the case of DFHv1
> when the registers are in a different location than the DFH.
> 
> > 
> > Thanks,
> > Yilun
> >