[v12,net-next,1/9] mfd: ocelot: add helper to get regmap from a resource

Commit Message

Colin Foster July 1, 2022, 7:26 p.m. UTC

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 <[e-mail]>
---
 MAINTAINERS                |  5 ++++
 include/linux/mfd/ocelot.h | 51 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 include/linux/mfd/ocelot.h

Comments

Andy Shevchenko July 1, 2022, 8:23 p.m. UTC | #1

On Fri, Jul 1, 2022 at 9:26 PM Colin Foster
<[e-mail]> 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.

...

> +       res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> +       if (res) {
> +               regs = devm_ioremap_resource(dev, res);
> +               if (IS_ERR(regs))
> +                       return ERR_CAST(regs);

Why can't it be devm_platform_get_and_ioremap_resource() here?

  regs = devm_platform_get_and_ioremap_resource();
  if (res) {
    if (IS_ERR(regs))
      return ERR_CAST();
   return ...
  }

> +               return devm_regmap_init_mmio(dev, regs, config);
> +       }

...

> +       return (map) ? map : ERR_PTR(-ENOENT);

Too many parentheses.

Also you may use short form of ternary operator:

       return map ?: ERR_PTR(-ENOENT);

Colin Foster July 1, 2022, 8:34 p.m. UTC | #2

On Fri, Jul 01, 2022 at 10:23:36PM +0200, Andy Shevchenko wrote:
> On Fri, Jul 1, 2022 at 9:26 PM Colin Foster
> <[e-mail]> 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.
> 
> ...
> 
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> > +       if (res) {
> > +               regs = devm_ioremap_resource(dev, res);
> > +               if (IS_ERR(regs))
> > +                       return ERR_CAST(regs);
> 
> Why can't it be devm_platform_get_and_ioremap_resource() here?

It can... but it invokes prints of "invalid resource" during
initialization.

Here it was implied that I should break the function call out:
https://patchwork.kernel.org/project/netdevbpf/patch/[e-mail]/#24917551

> 
>   regs = devm_platform_get_and_ioremap_resource();
>   if (res) {
>     if (IS_ERR(regs))
>       return ERR_CAST();
>    return ...
>   }
> 
> > +               return devm_regmap_init_mmio(dev, regs, config);
> > +       }
> 
> ...
> 
> > +       return (map) ? map : ERR_PTR(-ENOENT);
> 
> Too many parentheses.
> 
> Also you may use short form of ternary operator:
> 
>        return map ?: ERR_PTR(-ENOENT);

Agreed, and I didn't know about that operator. When Vladimir suggested
it I thought it was a typo. I should've known better.

> 
> -- 
> With Best Regards,
> Andy Shevchenko

Andy Shevchenko July 1, 2022, 8:41 p.m. UTC | #3

On Fri, Jul 1, 2022 at 10:35 PM Colin Foster
<[e-mail]> wrote:
> On Fri, Jul 01, 2022 at 10:23:36PM +0200, Andy Shevchenko wrote:
> > On Fri, Jul 1, 2022 at 9:26 PM Colin Foster
> > <[e-mail]> wrote:

...

> > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> > > +       if (res) {
> > > +               regs = devm_ioremap_resource(dev, res);
> > > +               if (IS_ERR(regs))
> > > +                       return ERR_CAST(regs);
> >
> > Why can't it be devm_platform_get_and_ioremap_resource() here?
>
> It can... but it invokes prints of "invalid resource" during
> initialization.
>
> Here it was implied that I should break the function call out:
> https://patchwork.kernel.org/project/netdevbpf/patch/[e-mail]/#24917551

Perhaps a comment in the code, so nobody will try to optimize this in
the future.

> > > +               return devm_regmap_init_mmio(dev, regs, config);
> > > +       }

...

> > > +       return (map) ? map : ERR_PTR(-ENOENT);
> >
> > Too many parentheses.
> >
> > Also you may use short form of ternary operator:
> >
> >        return map ?: ERR_PTR(-ENOENT);
>
> Agreed, and I didn't know about that operator. When Vladimir suggested
> it I thought it was a typo. I should've known better.

It's easy to remember by thinking of

"X ?: Y" as "X _or_ Y".

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 7c029ab73265..c2f61ed1b730 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14413,6 +14413,11 @@  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 <[e-mail]>
+S:	Supported
+F:	include/linux/mfd/ocelot.h
+
 OCXL (Open Coherent Accelerator Processor Interface OpenCAPI) DRIVER
 M:	Frederic Barrat <[e-mail]>
 M:	Andrew Donnellan <[e-mail]>
diff --git a/include/linux/mfd/ocelot.h b/include/linux/mfd/ocelot.h
new file mode 100644
index 000000000000..7e64870b75ca
--- /dev/null
+++ b/include/linux/mfd/ocelot.h
@@ -0,0 +1,51 @@ 
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/* Copyright 2022 Innovative Advantage Inc. */
+
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct resource;
+
+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;
+
+	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) ? map : ERR_PTR(-ENOENT);
+}