[PATCH/RFC 1/6] boot-mode-reg: Add core

[PATCH/RFC 1/6] boot-mode-reg: Add core

[Simon Horman]

The motivation for this new module is to add a small frame work to allow
kernel subsystems to obtain boot mode information from a centralised
source using a new, and hopefully soon well-known, API.

The new API consists of two function calls and nothing more:

boot_mode_reg_set: Should be called by platform-specific drivers
                   to register the boot mode register value which
		   they obtain from hardware or otherwise.

boot_mode_reg_get: Should be called by consumers; subsystems that
                   wish to know he boot mode register.

The boot mode register is a 32bit unsigned entity,
the meaning of its values are implementation dependent.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
---
 MAINTAINERS                         |  1 +
 drivers/misc/Kconfig                |  1 +
 drivers/misc/Makefile               |  1 +
 drivers/misc/boot-mode-reg/Kconfig  | 11 ++++++
 drivers/misc/boot-mode-reg/Makefile |  6 +++
 drivers/misc/boot-mode-reg/core.c   | 78 +++++++++++++++++++++++++++++++++++++
 include/misc/boot-mode-reg.h        | 24 ++++++++++++
 7 files changed, 122 insertions(+)
 create mode 100644 drivers/misc/boot-mode-reg/Kconfig
 create mode 100644 drivers/misc/boot-mode-reg/Makefile
 create mode 100644 drivers/misc/boot-mode-reg/core.c
 create mode 100644 include/misc/boot-mode-reg.h

diff --git a/MAINTAINERS b/MAINTAINERS
index e711675afbf7..3a0de82e617f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1495,6 +1495,7 @@ F:	arch/arm/configs/shmobile_defconfig
 F:	arch/arm/include/debug/renesas-scif.S
 F:	arch/arm/mach-shmobile/
 F:	drivers/sh/
+F:	drivers/misc/boot-mode-reg/
 
 ARM/SOCFPGA ARCHITECTURE
 M:	Dinh Nguyen <dinguyen@opensource.altera.com>
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index ccccc2943f2f..b6aa60cb8460 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -537,4 +537,5 @@ source "drivers/misc/mic/Kconfig"
 source "drivers/misc/genwqe/Kconfig"
 source "drivers/misc/echo/Kconfig"
 source "drivers/misc/cxl/Kconfig"
+source "drivers/misc/boot-mode-reg/Kconfig"
 endmenu
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 537d7f3b78da..0d1e8910c033 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -56,3 +56,4 @@ obj-$(CONFIG_GENWQE)		+= genwqe/
 obj-$(CONFIG_ECHO)		+= echo/
 obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
+obj-$(CONFIG_BOOT_MODE_REG_CORE)	+= boot-mode-reg/
diff --git a/drivers/misc/boot-mode-reg/Kconfig b/drivers/misc/boot-mode-reg/Kconfig
new file mode 100644
index 000000000000..806eba24238f
--- /dev/null
+++ b/drivers/misc/boot-mode-reg/Kconfig
@@ -0,0 +1,11 @@
+#
+# Boot Mode Register Drivers
+#
+
+config BOOT_MODE_REG_CORE
+	tristate "Boot Mode Register Core Driver"
+	default n
+	depends on ARCH_SHMOBILE || COMPILE_TEST
+	help
+	  Say Y here to allow support for drivers to read boot mode
+	  registers and make the value available to other subsystems.
diff --git a/drivers/misc/boot-mode-reg/Makefile b/drivers/misc/boot-mode-reg/Makefile
new file mode 100644
index 000000000000..19134b20a7f1
--- /dev/null
+++ b/drivers/misc/boot-mode-reg/Makefile
@@ -0,0 +1,6 @@
+
+#
+# Makefile for misc devices that really don't fit anywhere else.
+#
+
+obj-$(CONFIG_BOOT_MODE_REG_CORE)	+= core.o
diff --git a/drivers/misc/boot-mode-reg/core.c b/drivers/misc/boot-mode-reg/core.c
new file mode 100644
index 000000000000..9d7d72f52132
--- /dev/null
+++ b/drivers/misc/boot-mode-reg/core.c
@@ -0,0 +1,78 @@
+/*
+ * Boot Mode Register
+ *
+ * Copyright (C) 2015 Simon Horman
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <asm/errno.h>
+
+#include <linux/export.h>
+#include <linux/module.h>
+
+#include <misc/boot-mode-reg.h>
+
+static DEFINE_MUTEX(boot_mode_mutex);
+static bool boot_mode_is_set;
+static u32 boot_mode;
+
+/**
+ * boot_mode_reg_get() - retrieve boot mode register value
+ * @mode: implementation-dependent boot mode register value
+ *
+ * Retrieves the boot mode register value previously registered
+ * using boot_mode_reg_set().
+ *
+ * return: 0 on success
+ */
+int boot_mode_reg_get(u32 *mode)
+{
+	int err = -ENOENT;
+
+	mutex_lock(&boot_mode_mutex);
+	if (!boot_mode_is_set)
+		goto err;
+	*mode = boot_mode;
+	err = 0;
+err:
+	mutex_unlock(&boot_mode_mutex);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(boot_mode_get);
+
+/**
+ * boot_mode_reg_set() - record boot mode register value
+ * @mode: implementation-dependent boot mode register value
+ *
+ * Records the boot mode register value which may subsequently
+ * be retrieved using boot_mode_reg_get().
+ *
+ * return: 0 on success
+ */
+int boot_mode_reg_set(u32 mode)
+{
+	int err = -EBUSY;
+
+	mutex_lock(&boot_mode_mutex);
+	if (boot_mode_is_set && boot_mode != mode)
+		goto err;
+	boot_mode = mode;
+	boot_mode_is_set = true;
+	err = 0;
+err:
+	mutex_unlock(&boot_mode_mutex);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(boot_mode_set);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Simon Horman <horms@verge.net.au>");
+MODULE_DESCRIPTION("Core Boot Mode Register Driver");
diff --git a/include/misc/boot-mode-reg.h b/include/misc/boot-mode-reg.h
new file mode 100644
index 000000000000..34ee653279a4
--- /dev/null
+++ b/include/misc/boot-mode-reg.h
@@ -0,0 +1,24 @@
+/*
+ * Boot Mode Register
+ *
+ * Copyright (C) 2015 Simon Horman
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _BOOT_MODE_REG_H
+#define _BOOT_MODE_REG_H
+
+#include <linux/types.h>
+
+int boot_mode_reg_get(u32 *mode);
+int boot_mode_reg_set(u32 mode);
+
+#endif
-- 
2.1.4

Re: [PATCH/RFC 1/6] boot-mode-reg: Add core

[Geert Uytterhoeven]

On Thu, Oct 15, 2015 at 8:59 AM, Simon Horman
<horms+renesas@verge.net.au> wrote:
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/core.c
> @@ -0,0 +1,78 @@
> +/*
> + * Boot Mode Register
> + *
> + * Copyright (C) 2015 Simon Horman
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <asm/errno.h>
> +
> +#include <linux/export.h>
> +#include <linux/module.h>
> +
> +#include <misc/boot-mode-reg.h>
> +
> +static DEFINE_MUTEX(boot_mode_mutex);
> +static bool boot_mode_is_set;
> +static u32 boot_mode;
> +
> +/**
> + * boot_mode_reg_get() - retrieve boot mode register value
> + * @mode: implementation-dependent boot mode register value
> + *
> + * Retrieves the boot mode register value previously registered
> + * using boot_mode_reg_set().
> + *
> + * return: 0 on success
> + */
> +int boot_mode_reg_get(u32 *mode)
> +{
> +       int err = -ENOENT;
> +
> +       mutex_lock(&boot_mode_mutex);
> +       if (!boot_mode_is_set)
> +               goto err;
> +       *mode = boot_mode;
> +       err = 0;
> +err:
> +       mutex_unlock(&boot_mode_mutex);
> +       return 0;

return err;

> +}
> +EXPORT_SYMBOL_GPL(boot_mode_get);
> +
> +/**
> + * boot_mode_reg_set() - record boot mode register value
> + * @mode: implementation-dependent boot mode register value
> + *
> + * Records the boot mode register value which may subsequently
> + * be retrieved using boot_mode_reg_get().
> + *
> + * return: 0 on success
> + */
> +int boot_mode_reg_set(u32 mode)
> +{
> +       int err = -EBUSY;
> +
> +       mutex_lock(&boot_mode_mutex);
> +       if (boot_mode_is_set && boot_mode != mode)
> +               goto err;
> +       boot_mode = mode;
> +       boot_mode_is_set = true;
> +       err = 0;
> +err:
> +       mutex_unlock(&boot_mode_mutex);
> +       return 0;

return err;

> +}

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH/RFC 1/6] boot-mode-reg: Add core

[Khiem Nguyen]

Hi Simon,

Thanks for your patch.

On 10/15/2015 1:59 PM, Simon Horman wrote:
> The motivation for this new module is to add a small frame work to allow
> kernel subsystems to obtain boot mode information from a centralised
> source using a new, and hopefully soon well-known, API.
>
> The new API consists of two function calls and nothing more:
>
> boot_mode_reg_set: Should be called by platform-specific drivers
>                     to register the boot mode register value which
> 		   they obtain from hardware or otherwise.
>
> boot_mode_reg_get: Should be called by consumers; subsystems that
>                     wish to know he boot mode register.
>
> The boot mode register is a 32bit unsigned entity,
> the meaning of its values are implementation dependent.
>
> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
> ---
>   MAINTAINERS                         |  1 +
>   drivers/misc/Kconfig                |  1 +
>   drivers/misc/Makefile               |  1 +
>   drivers/misc/boot-mode-reg/Kconfig  | 11 ++++++
>   drivers/misc/boot-mode-reg/Makefile |  6 +++
>   drivers/misc/boot-mode-reg/core.c   | 78 +++++++++++++++++++++++++++++++++++++
>   include/misc/boot-mode-reg.h        | 24 ++++++++++++
>   7 files changed, 122 insertions(+)
>   create mode 100644 drivers/misc/boot-mode-reg/Kconfig
>   create mode 100644 drivers/misc/boot-mode-reg/Makefile
>   create mode 100644 drivers/misc/boot-mode-reg/core.c
>   create mode 100644 include/misc/boot-mode-reg.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e711675afbf7..3a0de82e617f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1495,6 +1495,7 @@ F:	arch/arm/configs/shmobile_defconfig
>   F:	arch/arm/include/debug/renesas-scif.S
>   F:	arch/arm/mach-shmobile/
>   F:	drivers/sh/
> +F:	drivers/misc/boot-mode-reg/
>
>   ARM/SOCFPGA ARCHITECTURE
>   M:	Dinh Nguyen <dinguyen@opensource.altera.com>
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index ccccc2943f2f..b6aa60cb8460 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -537,4 +537,5 @@ source "drivers/misc/mic/Kconfig"
>   source "drivers/misc/genwqe/Kconfig"
>   source "drivers/misc/echo/Kconfig"
>   source "drivers/misc/cxl/Kconfig"
> +source "drivers/misc/boot-mode-reg/Kconfig"
>   endmenu
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 537d7f3b78da..0d1e8910c033 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -56,3 +56,4 @@ obj-$(CONFIG_GENWQE)		+= genwqe/
>   obj-$(CONFIG_ECHO)		+= echo/
>   obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
>   obj-$(CONFIG_CXL_BASE)		+= cxl/
> +obj-$(CONFIG_BOOT_MODE_REG_CORE)	+= boot-mode-reg/
> diff --git a/drivers/misc/boot-mode-reg/Kconfig b/drivers/misc/boot-mode-reg/Kconfig
> new file mode 100644
> index 000000000000..806eba24238f
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/Kconfig
> @@ -0,0 +1,11 @@
> +#
> +# Boot Mode Register Drivers
> +#
> +
> +config BOOT_MODE_REG_CORE
> +	tristate "Boot Mode Register Core Driver"
> +	default n
> +	depends on ARCH_SHMOBILE || COMPILE_TEST
> +	help
> +	  Say Y here to allow support for drivers to read boot mode
> +	  registers and make the value available to other subsystems.
> diff --git a/drivers/misc/boot-mode-reg/Makefile b/drivers/misc/boot-mode-reg/Makefile
> new file mode 100644
> index 000000000000..19134b20a7f1
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/Makefile
> @@ -0,0 +1,6 @@
> +
> +#
> +# Makefile for misc devices that really don't fit anywhere else.
> +#
> +
> +obj-$(CONFIG_BOOT_MODE_REG_CORE)	+= core.o
> diff --git a/drivers/misc/boot-mode-reg/core.c b/drivers/misc/boot-mode-reg/core.c
> new file mode 100644
> index 000000000000..9d7d72f52132
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/core.c
> @@ -0,0 +1,78 @@
> +/*
> + * Boot Mode Register
> + *
> + * Copyright (C) 2015 Simon Horman
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <asm/errno.h>
> +
> +#include <linux/export.h>
> +#include <linux/module.h>
> +
> +#include <misc/boot-mode-reg.h>
> +
> +static DEFINE_MUTEX(boot_mode_mutex);
> +static bool boot_mode_is_set;
> +static u32 boot_mode;
> +
> +/**
> + * boot_mode_reg_get() - retrieve boot mode register value
> + * @mode: implementation-dependent boot mode register value
> + *
> + * Retrieves the boot mode register value previously registered
> + * using boot_mode_reg_set().
> + *
> + * return: 0 on success
> + */
> +int boot_mode_reg_get(u32 *mode)
> +{
> +	int err = -ENOENT;
> +
> +	mutex_lock(&boot_mode_mutex);
> +	if (!boot_mode_is_set)
> +		goto err;
> +	*mode = boot_mode;
> +	err = 0;
> +err:
> +	mutex_unlock(&boot_mode_mutex);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(boot_mode_get);

Lack of 'reg' in exported symbol, right ?
e.g EXPORT_SYMBOL_GPL(boot_mode_reg_get);

> +
> +/**
> + * boot_mode_reg_set() - record boot mode register value
> + * @mode: implementation-dependent boot mode register value
> + *
> + * Records the boot mode register value which may subsequently
> + * be retrieved using boot_mode_reg_get().
> + *
> + * return: 0 on success
> + */
> +int boot_mode_reg_set(u32 mode)
> +{
> +	int err = -EBUSY;
> +
> +	mutex_lock(&boot_mode_mutex);
> +	if (boot_mode_is_set && boot_mode != mode)
> +		goto err;
> +	boot_mode = mode;
> +	boot_mode_is_set = true;
> +	err = 0;
> +err:
> +	mutex_unlock(&boot_mode_mutex);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(boot_mode_set);

Lack of 'reg' in exported symbol, right ?
e.g EXPORT_SYMBOL_GPL(boot_mode_reg_set);

> +
> +MODULE_LICENSE("GPL");

The license should be GPLv2 to match with the paragraph at top of this 
file, right ?

> +MODULE_AUTHOR("Simon Horman <horms@verge.net.au>");
> +MODULE_DESCRIPTION("Core Boot Mode Register Driver");
> diff --git a/include/misc/boot-mode-reg.h b/include/misc/boot-mode-reg.h
> new file mode 100644
> index 000000000000..34ee653279a4
> --- /dev/null
> +++ b/include/misc/boot-mode-reg.h
> @@ -0,0 +1,24 @@
> +/*
> + * Boot Mode Register
> + *
> + * Copyright (C) 2015 Simon Horman
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef _BOOT_MODE_REG_H
> +#define _BOOT_MODE_REG_H
> +
> +#include <linux/types.h>
> +
> +int boot_mode_reg_get(u32 *mode);
> +int boot_mode_reg_set(u32 mode);
> +
> +#endif
>

Re: [PATCH/RFC 1/6] boot-mode-reg: Add core

[Laurent Pinchart]

Hi Simon,

Thank you for the patch.

On Thursday 15 October 2015 15:59:32 Simon Horman wrote:
> The motivation for this new module is to add a small frame work to allow
> kernel subsystems to obtain boot mode information from a centralised
> source using a new, and hopefully soon well-known, API.
> 
> The new API consists of two function calls and nothing more:
> 
> boot_mode_reg_set: Should be called by platform-specific drivers
>                    to register the boot mode register value which
> 		   they obtain from hardware or otherwise.
> 
> boot_mode_reg_get: Should be called by consumers; subsystems that
>                    wish to know he boot mode register.
> 
> The boot mode register is a 32bit unsigned entity,
> the meaning of its values are implementation dependent.

I believe this is where the bulk of the discussion will take place.

The boot mode get API is pretty straightforward. We might want to pass a boot 
mode structure pointer instead of an u32 *, but I believe that's a detail at 
this stage. I'll leave bikeshedding to others for now.

I had envisioned the set operation a bit differently, but that doesn't mean 
your proposal is bad. Just for the record, I was thinking of adding a macro 
similar to CLK_OF_DECLARE() to declare possible boot mode providers. The get 
operation would then walk through the list the first time it's called and try 
to get the boot mode from the provider(s) compatible with the running DT. The 
value would then be cached internally and returned on subsequent calls.

That approach would solve (or work around, depending on how you see it) the 
initcall ordering issue. initcall ordering is another point that I see as 
potentially leading to lengthy discussions, we need to think it through 
propery and define exactly when the boot mode is available to drivers or other 
kernel code.

> Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
> ---
>  MAINTAINERS                         |  1 +
>  drivers/misc/Kconfig                |  1 +
>  drivers/misc/Makefile               |  1 +
>  drivers/misc/boot-mode-reg/Kconfig  | 11 ++++++
>  drivers/misc/boot-mode-reg/Makefile |  6 +++
>  drivers/misc/boot-mode-reg/core.c   | 78 ++++++++++++++++++++++++++++++++++
>  include/misc/boot-mode-reg.h        | 24 ++++++++++++
>  7 files changed, 122 insertions(+)
>  create mode 100644 drivers/misc/boot-mode-reg/Kconfig
>  create mode 100644 drivers/misc/boot-mode-reg/Makefile
>  create mode 100644 drivers/misc/boot-mode-reg/core.c
>  create mode 100644 include/misc/boot-mode-reg.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e711675afbf7..3a0de82e617f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1495,6 +1495,7 @@ F:	arch/arm/configs/shmobile_defconfig
>  F:	arch/arm/include/debug/renesas-scif.S
>  F:	arch/arm/mach-shmobile/
>  F:	drivers/sh/
> +F:	drivers/misc/boot-mode-reg/
> 
>  ARM/SOCFPGA ARCHITECTURE
>  M:	Dinh Nguyen <dinguyen@opensource.altera.com>
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index ccccc2943f2f..b6aa60cb8460 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -537,4 +537,5 @@ source "drivers/misc/mic/Kconfig"
>  source "drivers/misc/genwqe/Kconfig"
>  source "drivers/misc/echo/Kconfig"
>  source "drivers/misc/cxl/Kconfig"
> +source "drivers/misc/boot-mode-reg/Kconfig"
>  endmenu
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 537d7f3b78da..0d1e8910c033 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -56,3 +56,4 @@ obj-$(CONFIG_GENWQE)		+= genwqe/
>  obj-$(CONFIG_ECHO)		+= echo/
>  obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
>  obj-$(CONFIG_CXL_BASE)		+= cxl/
> +obj-$(CONFIG_BOOT_MODE_REG_CORE)	+= boot-mode-reg/
> diff --git a/drivers/misc/boot-mode-reg/Kconfig
> b/drivers/misc/boot-mode-reg/Kconfig new file mode 100644
> index 000000000000..806eba24238f
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/Kconfig
> @@ -0,0 +1,11 @@
> +#
> +# Boot Mode Register Drivers
> +#
> +
> +config BOOT_MODE_REG_CORE
> +	tristate "Boot Mode Register Core Driver"
> +	default n
> +	depends on ARCH_SHMOBILE || COMPILE_TEST
> +	help
> +	  Say Y here to allow support for drivers to read boot mode
> +	  registers and make the value available to other subsystems.
> diff --git a/drivers/misc/boot-mode-reg/Makefile
> b/drivers/misc/boot-mode-reg/Makefile new file mode 100644
> index 000000000000..19134b20a7f1
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/Makefile
> @@ -0,0 +1,6 @@
> +
> +#
> +# Makefile for misc devices that really don't fit anywhere else.
> +#
> +
> +obj-$(CONFIG_BOOT_MODE_REG_CORE)	+= core.o
> diff --git a/drivers/misc/boot-mode-reg/core.c
> b/drivers/misc/boot-mode-reg/core.c new file mode 100644
> index 000000000000..9d7d72f52132
> --- /dev/null
> +++ b/drivers/misc/boot-mode-reg/core.c
> @@ -0,0 +1,78 @@
> +/*
> + * Boot Mode Register
> + *
> + * Copyright (C) 2015 Simon Horman
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <asm/errno.h>
> +
> +#include <linux/export.h>
> +#include <linux/module.h>
> +
> +#include <misc/boot-mode-reg.h>
> +
> +static DEFINE_MUTEX(boot_mode_mutex);
> +static bool boot_mode_is_set;
> +static u32 boot_mode;
> +
> +/**
> + * boot_mode_reg_get() - retrieve boot mode register value
> + * @mode: implementation-dependent boot mode register value
> + *
> + * Retrieves the boot mode register value previously registered
> + * using boot_mode_reg_set().
> + *
> + * return: 0 on success
> + */
> +int boot_mode_reg_get(u32 *mode)
> +{
> +	int err = -ENOENT;
> +
> +	mutex_lock(&boot_mode_mutex);
> +	if (!boot_mode_is_set)
> +		goto err;
> +	*mode = boot_mode;
> +	err = 0;
> +err:
> +	mutex_unlock(&boot_mode_mutex);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(boot_mode_get);
> +
> +/**
> + * boot_mode_reg_set() - record boot mode register value
> + * @mode: implementation-dependent boot mode register value
> + *
> + * Records the boot mode register value which may subsequently
> + * be retrieved using boot_mode_reg_get().
> + *
> + * return: 0 on success
> + */
> +int boot_mode_reg_set(u32 mode)
> +{
> +	int err = -EBUSY;
> +
> +	mutex_lock(&boot_mode_mutex);
> +	if (boot_mode_is_set && boot_mode != mode)
> +		goto err;
> +	boot_mode = mode;
> +	boot_mode_is_set = true;
> +	err = 0;
> +err:
> +	mutex_unlock(&boot_mode_mutex);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(boot_mode_set);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Simon Horman <horms@verge.net.au>");
> +MODULE_DESCRIPTION("Core Boot Mode Register Driver");
> diff --git a/include/misc/boot-mode-reg.h b/include/misc/boot-mode-reg.h
> new file mode 100644
> index 000000000000..34ee653279a4
> --- /dev/null
> +++ b/include/misc/boot-mode-reg.h
> @@ -0,0 +1,24 @@
> +/*
> + * Boot Mode Register
> + *
> + * Copyright (C) 2015 Simon Horman
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef _BOOT_MODE_REG_H
> +#define _BOOT_MODE_REG_H
> +
> +#include <linux/types.h>
> +
> +int boot_mode_reg_get(u32 *mode);
> +int boot_mode_reg_set(u32 mode);
> +
> +#endif

-- 
Regards,

Laurent Pinchart

Re: [PATCH/RFC 1/6] boot-mode-reg: Add core

[Simon Horman]

Hi Laurent,

On Fri, Oct 23, 2015 at 05:11:56PM +0300, Laurent Pinchart wrote:
> Hi Simon,
> 
> Thank you for the patch.
> 
> On Thursday 15 October 2015 15:59:32 Simon Horman wrote:
> > The motivation for this new module is to add a small frame work to allow
> > kernel subsystems to obtain boot mode information from a centralised
> > source using a new, and hopefully soon well-known, API.
> > 
> > The new API consists of two function calls and nothing more:
> > 
> > boot_mode_reg_set: Should be called by platform-specific drivers
> >                    to register the boot mode register value which
> > 		   they obtain from hardware or otherwise.
> > 
> > boot_mode_reg_get: Should be called by consumers; subsystems that
> >                    wish to know he boot mode register.
> > 
> > The boot mode register is a 32bit unsigned entity,
> > the meaning of its values are implementation dependent.
> 
> I believe this is where the bulk of the discussion will take place.
> 
> The boot mode get API is pretty straightforward. We might want to pass a
> boot mode structure pointer instead of an u32 *, but I believe that's a
> detail at this stage. I'll leave bikeshedding to others for now.
> 
> I had envisioned the set operation a bit differently, but that doesn't
> mean your proposal is bad. Just for the record, I was thinking of adding
> a macro similar to CLK_OF_DECLARE() to declare possible boot mode
> providers. The get operation would then walk through the list the first
> time it's called and try to get the boot mode from the provider(s)
> compatible with the running DT. The value would then be cached internally
> and returned on subsequent calls.
> 
> That approach would solve (or work around, depending on how you see it)
> the initcall ordering issue. initcall ordering is another point that I
> see as potentially leading to lengthy discussions, we need to think it
> through propery and define exactly when the boot mode is available to
> drivers or other kernel code.

Thanks.

I apologise if you had mentioned this to me before, if so I must
have misunderstood it because I did not consider using a CLK_OF_DECLARE()
variant before now.

I have now taken a look at it and it does seem to quite nicely
side-step the initcall / earlyboot ordering problem. I took a stab
at implementing the idea and it seemed to come out quite cleanly
(and worked first go!).

What did is in the incremental patch on top of the entire series below.
It also includes a few other minor cleanups - correcting error handing
and EXPORT_SYMBOL_GPL names.

Could you see if it is to your liking? Of course I will
break up the patch and squash the appropriate portions into the
patches of this series before any formal posting of it.


diff --git a/arch/arm/mach-shmobile/setup-rcar-gen2.c b/arch/arm/mach-shmobile/setup-rcar-gen2.c
index 403ee0ede379..8aba1c4c2a62 100644
--- a/arch/arm/mach-shmobile/setup-rcar-gen2.c
+++ b/arch/arm/mach-shmobile/setup-rcar-gen2.c
@@ -121,10 +121,7 @@ void __init rcar_gen2_timer_init(void)
 {
 	int err;
 
-	err = rcar_gen2_init_boot_mode();
-	if (err)
-		pr_err("Could not initialise boot mode register driver\n");
-
+	boot_mode_reg_of_init();
 	rcar_gen2_timer_init_for_arch_timer();
 	rcar_gen2_clocks_init();
 	clocksource_of_init();
diff --git a/drivers/misc/boot-mode-reg/core.c b/drivers/misc/boot-mode-reg/core.c
index 9d7d72f52132..f50d84b8c65d 100644
--- a/drivers/misc/boot-mode-reg/core.c
+++ b/drivers/misc/boot-mode-reg/core.c
@@ -44,9 +44,9 @@ int boot_mode_reg_get(u32 *mode)
 	err = 0;
 err:
 	mutex_unlock(&boot_mode_mutex);
-	return 0;
+	return err;
 }
-EXPORT_SYMBOL_GPL(boot_mode_get);
+EXPORT_SYMBOL_GPL(boot_mode_reg_get);
 
 /**
  * boot_mode_reg_set() - record boot mode register value
@@ -54,25 +54,47 @@ EXPORT_SYMBOL_GPL(boot_mode_get);
  *
  * Records the boot mode register value which may subsequently
  * be retrieved using boot_mode_reg_get().
- *
- * return: 0 on success
  */
-int boot_mode_reg_set(u32 mode)
+void boot_mode_reg_set(u32 mode)
 {
-	int err = -EBUSY;
-
 	mutex_lock(&boot_mode_mutex);
-	if (boot_mode_is_set && boot_mode != mode)
+	if (boot_mode_is_set && boot_mode != mode) {
+		pr_err("boot mode register value already registered");
 		goto err;
+	}
 	boot_mode = mode;
 	boot_mode_is_set = true;
-	err = 0;
-err:
 	mutex_unlock(&boot_mode_mutex);
-	return 0;
+err:
+	return;
 }
-EXPORT_SYMBOL_GPL(boot_mode_set);
+EXPORT_SYMBOL_GPL(boot_mode_reg_set);
+
+
+#include <linux/init.h>
+#include <linux/of.h>
+
+extern struct of_device_id __boot_mode_reg_of_table[];
 
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Simon Horman <horms@verge.net.au>");
-MODULE_DESCRIPTION("Core Boot Mode Register Driver");
+static const struct of_device_id __boot_mode_reg_of_table_sentinel
+	__used __section(__boot_mode_reg_of_table_end);
+
+void __init boot_mode_reg_of_init(void)
+{
+	struct device_node *np;
+	const struct of_device_id *match;
+
+	for_each_matching_node_and_match(np, __boot_mode_reg_of_table, &match) {
+		of_init_fn_1 init_func;
+
+		if (!of_device_is_available(np))
+			continue;
+
+		init_func = match->data;
+		init_func(np);
+
+		return;
+	}
+
+	pr_warn("%s: no matching boot mode reg providor found\n", __func__);
+}
diff --git a/drivers/misc/boot-mode-reg/rcar-gen2.c b/drivers/misc/boot-mode-reg/rcar-gen2.c
index 0f1a06fcf094..3970c9ffc38e 100644
--- a/drivers/misc/boot-mode-reg/rcar-gen2.c
+++ b/drivers/misc/boot-mode-reg/rcar-gen2.c
@@ -21,40 +21,35 @@
 
 #define MODEMR 0xe6160060
 
-static int __init rcar_gen2_read_mode_pins(void)
+static void __init rcar_gen2_read_mode_pins(void)
 {
 	void __iomem *modemr;
-	int err = -ENOMEM;
 	static u32 mode;
 
 	modemr = ioremap_nocache(MODEMR, 4);
 	if (!modemr) {
 		pr_err("failed to map boot mode register");
-		goto err;
+		return;
 	}
 	mode = ioread32(modemr);
 	iounmap(modemr);
 
-	err = boot_mode_reg_set(mode);
-err:
-	if (err)
-		pr_err("failed to initialise boot mode");
-	return err;
+	boot_mode_reg_set(mode);
 }
 
-int __init rcar_gen2_init_boot_mode(void)
+static void __init rcar_gen2_init(struct device_node *np)
 {
-	if (of_machine_is_compatible("renesas,r8a7790") ||
-	    of_machine_is_compatible("renesas,r8a7791") ||
-	    of_machine_is_compatible("renesas,r8a7792") ||
-	    of_machine_is_compatible("renesas,r8a7793") ||
-	    of_machine_is_compatible("renesas,r8a7794"))
-		return rcar_gen2_read_mode_pins();
-
-	return 0;
+	rcar_gen2_read_mode_pins();
 }
-EXPORT_SYMBOL_GPL(boot_mode_set);
-early_initcall(rcar_gen2_init_boot_mode);
+
+#define RCAR_GEN2_BOOT_MODE_REG_OF_DECLARE(name) \
+	BOOT_MODE_REG_OF_DECLARE(name, "renesas," #name, rcar_gen2_init);
+
+RCAR_GEN2_BOOT_MODE_REG_OF_DECLARE(r8a7790);
+RCAR_GEN2_BOOT_MODE_REG_OF_DECLARE(r8a7791);
+RCAR_GEN2_BOOT_MODE_REG_OF_DECLARE(r8a7792);
+RCAR_GEN2_BOOT_MODE_REG_OF_DECLARE(r8a7793);
+RCAR_GEN2_BOOT_MODE_REG_OF_DECLARE(r8a7794);
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Simon Horman <horms@verge.net.au>");
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1781e54ea6d3..875afce4827d 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -180,6 +180,8 @@
 #define CPU_METHOD_OF_TABLES()	OF_TABLE(CONFIG_SMP, cpu_method)
 #define CPUIDLE_METHOD_OF_TABLES() OF_TABLE(CONFIG_CPU_IDLE, cpuidle_method)
 #define EARLYCON_OF_TABLES()	OF_TABLE(CONFIG_SERIAL_EARLYCON, earlycon)
+#define BOOT_MODE_REG_OF_TABLES() OF_TABLE(CONFIG_BOOT_MODE_REG_CORE,   \
+						 boot_mode_reg)
 
 #define KERNEL_DTB()							\
 	STRUCT_ALIGN();							\
@@ -515,7 +517,8 @@
 	KERNEL_DTB()							\
 	IRQCHIP_OF_MATCH_TABLE()					\
 	EARLYCON_TABLE()						\
-	EARLYCON_OF_TABLES()
+	EARLYCON_OF_TABLES()						\
+	BOOT_MODE_REG_OF_TABLES()
 
 #define INIT_TEXT							\
 	*(.init.text)							\
diff --git a/include/misc/boot-mode-reg.h b/include/misc/boot-mode-reg.h
index f8fea0ea5a3e..dacfa94373e4 100644
--- a/include/misc/boot-mode-reg.h
+++ b/include/misc/boot-mode-reg.h
@@ -19,9 +19,14 @@
 #include <linux/types.h>
 
 int boot_mode_reg_get(u32 *mode);
-int boot_mode_reg_set(u32 mode);
+void boot_mode_reg_set(u32 mode);
 
-/* Allow explicit initialisation before initcalls */
-int rcar_gen2_init_boot_mode(void);
+
+void boot_mode_reg_of_init(void);
+
+#define BOOT_MODE_REG_OF_DECLARE(name, compat, fn)                      \
+       static const struct of_device_id __boot_mode_reg_of_table_##name \
+               __used __section(__boot_mode_reg_of_table)               \
+                = { .compatible = compat, .data = fn };
 
 #endif

Re: [PATCH/RFC 1/6] boot-mode-reg: Add core

[Geert Uytterhoeven]

Hi Laurent,

On Fri, Oct 23, 2015 at 4:11 PM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> I had envisioned the set operation a bit differently, but that doesn't mean
> your proposal is bad. Just for the record, I was thinking of adding a macro
> similar to CLK_OF_DECLARE() to declare possible boot mode providers. The get
> operation would then walk through the list the first time it's called and try
> to get the boot mode from the provider(s) compatible with the running DT. The
> value would then be cached internally and returned on subsequent calls.

You may have gotten a different impressions from the cpg/mssr thread, but
I don't like these *_OF_DECLARE() statements at all. It's one more ordering
hack, we already had too many of.

As this is supposed to be a generic solution, what if on some SoC the hardware
block providing the mode register has a dependency like a clock or PM domain
or regulator?

At least syscon_regmap_lookup_by_phandle() (which I used for my
"renesas,modemr" proposal in the CPG driver) will cause the syscon node to
be probed if it doesn't exist yet. And a future generic solution to solve
the phandle dependency issues should do that, too.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds