linux-kernel - Re: [PATCH v4 3/4] fpga: dfl: add basic support DFHv1

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Message-ID: <97f6047-e364-8ae7-195c-4cf33c4b3ec7@linux.intel.com>
Date:   Fri, 21 Oct 2022 11:58:14 +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, macro@...am.me.uk,
        johan@...nel.org, Lukas Wunner <lukas@...ner.de>,
        marpagan@...hat.com
Subject: Re: [PATCH v4 3/4] fpga: dfl: add basic support DFHv1

On Thu, 20 Oct 2022, matthew.gerlach@...ux.intel.com wrote:

> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> 
> Add generic support for MSI-X 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@...ux.intel.com>
> ---
> v4: s/MSIX/MSI_X
>     move kernel doc to implementation
>     use structure assignment
>     fix decode of absolute address
>     clean up comment in parse_feature_irqs
>     remove use of csr_res
> 
> 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
> ---

> +static int dfh_get_psize(void __iomem *dfh_base, resource_size_t max)
> +{
> +	int size = 0;
> +	u64 v, next;
> +
> +	if (!FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS,
> +		       readq(dfh_base + DFHv1_CSR_SIZE_GRP)))
> +		return 0;
> +
> +	while (size + DFHv1_PARAM_HDR < max) {
> +		v = readq(dfh_base + DFHv1_PARAM_HDR + size);
> +
> +		next = FIELD_GET(DFHv1_PARAM_HDR_NEXT_OFFSET, v);
> +		if (!(next & ~DFHv1_PARAM_HDR_NEXT_MASK))

In general, try to not use inverse logic for defining masks. However here, 
just change DFHv1_PARAM_HDR_NEXT_OFFSET to not include any extra bits 
(no rsvd nor eop) and you no longer need this extra masking.

> +			return -EINVAL;
> +
> +		size += next & ~DFHv1_PARAM_HDR_NEXT_MASK;

...Then you can drop this anding too.

> +
> +		if (next & DFHv1_PARAM_HDR_NEXT_EOL)

Your docs say EOP, but here you use EOL.

Change DFHv1_PARAM_HDR_NEXT_EOL such that this is extracted directly from 
v.

-- 
 i.