rtc: add generic nvmem support

Many RTCs have an on board non volatile storage. It can be battery backed
RAM or an EEPROM. Use the nvmem subsystem to export it to both userspace
and in-kernel consumers.

This stays compatible with the previous (non documented) ABI that was using
/sys/class/rtc/rtcx/device/nvram to export that memory. But will warn about
the deprecation.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt
index 47feb4414b7e1ff3107c73e681323095b4745781..c0c977445fb9ca732e45acf1ddbf787f9398315d 100644 (file)
--- a/Documentation/rtc.txt
+++ b/Documentation/rtc.txt
@@ -164,6 +164,8 @@ offset               The amount which the rtc clock has been adjusted in firmware.
                 which are added to or removed from the rtc's base clock per
                 billion ticks. A positive value makes a day pass more slowly,
                 longer, and a negative value makes a day pass more quickly.
+*/nvmem                 The non volatile storage exported as a raw file, as described
+                in Documentation/nvmem/nvmem.txt
 ================ ==============================================================
 
 IOCTL interface

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index d0e4b4a1c2a1e4c73701ae84fdfb53516fbae0d7..72419ac2c52a91345c69dcd4aaee6de1f585b35d 100644 (file)
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -77,6 +77,14 @@ config RTC_DEBUG
          Say yes here to enable debugging support in the RTC framework
          and individual RTC drivers.
 
+config RTC_NVMEM
+       bool "RTC non volatile storage support"
+       select NVMEM
+       default RTC_CLASS
+       help
+         Say yes here to add support for the non volatile (often battery
+         backed) storage present on RTCs.
+
 comment "RTC interfaces"
 
 config RTC_INTF_SYSFS

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 4050fc8b9271b7bdbf874c2ac92cdab9837a2bca..acd366b41c854b390f773f8b6dd6f16e4c786fc9 100644 (file)
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -15,6 +15,7 @@ ifdef CONFIG_RTC_DRV_EFI
 rtc-core-y                     += rtc-efi-platform.o
 endif
 
+rtc-core-$(CONFIG_RTC_NVMEM)           += nvmem.o
 rtc-core-$(CONFIG_RTC_INTF_DEV)                += rtc-dev.o
 rtc-core-$(CONFIG_RTC_INTF_PROC)       += rtc-proc.o
 rtc-core-$(CONFIG_RTC_INTF_SYSFS)      += rtc-sysfs.o

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 58e2a05765bbc35cd16442ec202387f647c0f2f5..2ed970d61da140c23a266e43a8b3b6b0eae8914d 100644 (file)
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -290,6 +290,8 @@ EXPORT_SYMBOL_GPL(rtc_device_register);
  */
 void rtc_device_unregister(struct rtc_device *rtc)
 {
+       rtc_nvmem_unregister(rtc);
+
        mutex_lock(&rtc->ops_lock);
        /*
         * Remove innards of this RTC, then disable it, before
@@ -448,6 +450,8 @@ int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
 
        rtc_proc_add_device(rtc);
 
+       rtc_nvmem_register(rtc);
+
        rtc->registered = true;
        dev_info(rtc->dev.parent, "registered as %s\n",
                 dev_name(&rtc->dev));

diff --git a/drivers/rtc/nvmem.c b/drivers/rtc/nvmem.c
new file mode 100644 (file)
index 0000000..8567b4e
--- /dev/null
+++ b/drivers/rtc/nvmem.c
@@ -0,0 +1,113 @@
+/*
+ * RTC subsystem, nvmem interface
+ *
+ * Copyright (C) 2017 Alexandre Belloni
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/err.h>
+#include <linux/types.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/rtc.h>
+#include <linux/sysfs.h>
+
+#include "rtc-core.h"
+
+/*
+ * Deprecated ABI compatibility, this should be removed at some point
+ */
+
+static const char nvram_warning[] = "Deprecated ABI, please use nvmem";
+
+static ssize_t
+rtc_nvram_read(struct file *filp, struct kobject *kobj,
+              struct bin_attribute *attr,
+              char *buf, loff_t off, size_t count)
+{
+       struct rtc_device *rtc = attr->private;
+
+       dev_warn_once(kobj_to_dev(kobj), nvram_warning);
+
+       return nvmem_device_read(rtc->nvmem, off, count, buf);
+}
+
+static ssize_t
+rtc_nvram_write(struct file *filp, struct kobject *kobj,
+               struct bin_attribute *attr,
+               char *buf, loff_t off, size_t count)
+{
+       struct rtc_device *rtc = attr->private;
+
+       dev_warn_once(kobj_to_dev(kobj), nvram_warning);
+
+       return nvmem_device_write(rtc->nvmem, off, count, buf);
+}
+
+static int rtc_nvram_register(struct rtc_device *rtc)
+{
+       int err;
+
+       rtc->nvram = devm_kzalloc(rtc->dev.parent,
+                               sizeof(struct bin_attribute),
+                               GFP_KERNEL);
+       if (!rtc->nvram)
+               return -ENOMEM;
+
+       rtc->nvram->attr.name = "nvram";
+       rtc->nvram->attr.mode = 0644;
+       rtc->nvram->private = rtc;
+
+       sysfs_bin_attr_init(rtc->nvram);
+
+       rtc->nvram->read = rtc_nvram_read;
+       rtc->nvram->write = rtc_nvram_write;
+       rtc->nvram->size = rtc->nvmem_config->size;
+
+       err = sysfs_create_bin_file(&rtc->dev.parent->kobj,
+                                   rtc->nvram);
+       if (err) {
+               devm_kfree(rtc->dev.parent, rtc->nvram);
+               rtc->nvram = NULL;
+       }
+
+       return err;
+}
+
+static void rtc_nvram_unregister(struct rtc_device *rtc)
+{
+       sysfs_remove_bin_file(&rtc->dev.parent->kobj, rtc->nvram);
+}
+
+/*
+ * New ABI, uses nvmem
+ */
+void rtc_nvmem_register(struct rtc_device *rtc)
+{
+       if (!rtc->nvmem_config)
+               return;
+
+       rtc->nvmem_config->dev = &rtc->dev;
+       rtc->nvmem_config->owner = rtc->owner;
+       rtc->nvmem = nvmem_register(rtc->nvmem_config);
+       if (IS_ERR_OR_NULL(rtc->nvmem))
+               return;
+
+       /* Register the old ABI */
+       if (rtc->nvram_old_abi)
+               rtc_nvram_register(rtc);
+}
+
+void rtc_nvmem_unregister(struct rtc_device *rtc)
+{
+       if (IS_ERR_OR_NULL(rtc->nvmem))
+               return;
+
+       /* unregister the old ABI */
+       if (rtc->nvram)
+               rtc_nvram_unregister(rtc);
+
+       nvmem_unregister(rtc->nvmem);
+}

diff --git a/drivers/rtc/rtc-core.h b/drivers/rtc/rtc-core.h
index 7a4ed2f7c7d7dfcd531654d355d8ef4c23b082c5..ecab76a3207c08e2fd9ad58772bbde3104018154 100644 (file)
--- a/drivers/rtc/rtc-core.h
+++ b/drivers/rtc/rtc-core.h
@@ -45,3 +45,11 @@ static inline const struct attribute_group **rtc_get_dev_attribute_groups(void)
        return NULL;
 }
 #endif
+
+#ifdef CONFIG_RTC_NVMEM
+void rtc_nvmem_register(struct rtc_device *rtc);
+void rtc_nvmem_unregister(struct rtc_device *rtc);
+#else
+static inline void rtc_nvmem_register(struct rtc_device *rtc) {}
+static inline void rtc_nvmem_unregister(struct rtc_device *rtc) {}
+#endif

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 8e4a5f44f59ef5aebac909d57d81ee2d234df83b..d53ecdc060cfd926f00ab188c4866bb6b254ce7b 100644 (file)
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -14,6 +14,7 @@
 
 #include <linux/types.h>
 #include <linux/interrupt.h>
+#include <linux/nvmem-provider.h>
 #include <uapi/linux/rtc.h>
 
 extern int rtc_month_days(unsigned int month, unsigned int year);
@@ -144,6 +145,12 @@ struct rtc_device {
 
        bool registered;
 
+       struct nvmem_config *nvmem_config;
+       struct nvmem_device *nvmem;
+       /* Old ABI support */
+       bool nvram_old_abi;
+       struct bin_attribute *nvram;
+
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
        struct work_struct uie_task;
        struct timer_list uie_timer;