linux-kernel - Re: [PATCH v13 net-next 1/9] mfd: ocelot: add helper to get regmap from a resource

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Date:   Sat, 9 Jul 2022 18:56:15 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Colin Foster <colin.foster@...advantage.com>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Wolfram Sang <wsa@...nel.org>,
        Terry Bowman <terry.bowman@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "katie.morris@...advantage.com" <katie.morris@...advantage.com>
Subject: Re: [PATCH v13 net-next 1/9] mfd: ocelot: add helper to get regmap
 from a resource

On Tue, Jul 05, 2022 at 01:47:35PM -0700, Colin Foster wrote:
> Several ocelot-related modules are designed for MMIO / regmaps. As such,
> they often use a combination of devm_platform_get_and_ioremap_resource and
> devm_regmap_init_mmio.
> 
> Operating in an MFD might be different, in that it could be memory mapped,
> or it could be SPI, I2C... In these cases a fallback to use IORESOURCE_REG
> instead of IORESOURCE_MEM becomes necessary.
> 
> When this happens, there's redundant logic that needs to be implemented in
> every driver. In order to avoid this redundancy, utilize a single function
> that, if the MFD scenario is enabled, will perform this fallback logic.
> 
> Signed-off-by: Colin Foster <colin.foster@...advantage.com>
> ---

To me this looks good, I'll just add a few minor comments which I think
you don't necessarily need to address by resending, they're just things
I noticed.

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>

>  MAINTAINERS                |  5 ++++
>  include/linux/mfd/ocelot.h | 55 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+)
>  create mode 100644 include/linux/mfd/ocelot.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 28108e4fdb8f..f781caceeb38 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14467,6 +14467,11 @@ F:	net/dsa/tag_ocelot.c
>  F:	net/dsa/tag_ocelot_8021q.c
>  F:	tools/testing/selftests/drivers/net/ocelot/*
>  
> +OCELOT EXTERNAL SWITCH CONTROL
> +M:	Colin Foster <colin.foster@...advantage.com>
> +S:	Supported
> +F:	include/linux/mfd/ocelot.h
> +
>  OCXL (Open Coherent Accelerator Processor Interface OpenCAPI) DRIVER
>  M:	Frederic Barrat <fbarrat@...ux.ibm.com>
>  M:	Andrew Donnellan <ajd@...ux.ibm.com>
> diff --git a/include/linux/mfd/ocelot.h b/include/linux/mfd/ocelot.h
> new file mode 100644
> index 000000000000..353b7c2ee445
> --- /dev/null
> +++ b/include/linux/mfd/ocelot.h
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: GPL-2.0 OR MIT */
> +/* Copyright 2022 Innovative Advantage Inc. */

A header file should have ifdefs which should prevent double inclusion,
like

#ifndef _MFD_OCELOT_H
#define _MFD_OCELOT_H

...

#endif

> +
> +#include <linux/err.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>
> +
> +struct resource;

IMO if include/linux/platform_device.h doesn't provide "struct resource"
that's a problem for that header to solve, not for its users.

> +
> +static inline struct regmap *
> +ocelot_regmap_from_resource_optional(struct platform_device *pdev,
> +				     unsigned int index,
> +				     const struct regmap_config *config)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct resource *res;
> +	u32 __iomem *regs;

"regs" could be void *.

> +
> +	/*
> +	 * Don't use get_and_ioremap_resource here, since that will invoke
> +	 * prints of "invalid resource" which simply add confusion
> +	 */
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> +	if (res) {
> +		regs = devm_ioremap_resource(dev, res);
> +		if (IS_ERR(regs))
> +			return ERR_CAST(regs);
> +		return devm_regmap_init_mmio(dev, regs, config);
> +	}
> +
> +	/*
> +	 * Fall back to using REG and getting the resource from the parent
> +	 * device, which is possible in an MFD configuration
> +	 */
> +	if (dev->parent) {
> +		res = platform_get_resource(pdev, IORESOURCE_REG, index);
> +		if (!res)
> +			return NULL;
> +
> +		return dev_get_regmap(dev->parent, res->name);
> +	}
> +
> +	return NULL;
> +}
> +
> +static inline struct regmap *
> +ocelot_regmap_from_resource(struct platform_device *pdev, unsigned int index,
> +			    const struct regmap_config *config)
> +{
> +	struct regmap *map;
> +
> +	map = ocelot_regmap_from_resource_optional(pdev, index, config);
> +	return map ?: ERR_PTR(-ENOENT);
> +}
> -- 
> 2.25.1
>