[U-Boot] [PATCH 3/3] bootcount: add DM-based backing store for bootcount
Simon Glass
sjg at chromium.org
Thu Aug 23 10:45:11 UTC 2018
Hi Philipp,
On 17 August 2018 at 06:56, Dr. Philipp Tomsich
<philipp.tomsich at theobroma-systems.com> wrote:
> Simon,
>
> On 17 Aug 2018, at 14:49, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Philipp,
>
> On 14 August 2018 at 05:39, Dr. Philipp Tomsich
> <philipp.tomsich at theobroma-systems.com> wrote:
>
> Lukasz,
>
> On 14 Aug 2018, at 13:10, Lukasz Majewski <lukma at denx.de> wrote:
>
> Hi Philipp,
>
> The original bootcount methods do not provide an interface to DM and
> rely on a static configuration for I2C devices (e.g. bus, chip-addr,
> etc. are configured through defines statically). On a modern system
> that exposes multiple devices in a DTS-configurable way, this is less
> than optimal and a interface to DM-based devices will be desirable.
>
> This adds a simple driver that is DM-aware and configurable via DTS:
> the /chosen/u-boot,bootcount-device property is used to detect the DM
> device storing the bootcount and deviceclass-specific commands are
> used to read/write the bootcount.
>
> Initially, this provides support for the following DM devices:
> * RTC devices implementing the read8/write8 ops
>
> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> Tested-by: Klaus Goger <klaus.goger at theobroma-systems.com>
> ---
>
> doc/device-tree-bindings/chosen.txt | 27 +++++++++++
> drivers/bootcount/Kconfig | 12 +++++
> drivers/bootcount/Makefile | 1 +
> drivers/bootcount/bootcount_dm.c | 93
> +++++++++++++++++++++++++++++++++++++ 4 files changed, 133
> insertions(+) create mode 100644 drivers/bootcount/bootcount_dm.c
>
> diff --git a/doc/device-tree-bindings/chosen.txt
> b/doc/device-tree-bindings/chosen.txt index da7b4e6..734fd15 100644
> --- a/doc/device-tree-bindings/chosen.txt
> +++ b/doc/device-tree-bindings/chosen.txt
> @@ -42,6 +42,33 @@ Example
> };
> };
>
> +u-boot,bootcount-device property
> +--------------------------------
> +In a DM-based system, the bootcount may be stored in a device known
> to +the DM framework (e.g. in a battery-backed SRAM area within a RTC
> +device). To identify the device to be used for the bootcount, the
> +u-boot,bootcount-device property needs to point to the target device.
> +
> +Further configuration in the target device's node may be required
> +(e.g. an offset into an I2C RTC's address space), depending on the
> +UCLASS of the target device.
> +
> +Example
> +-------
> +/ {
> + chosen {
> + u-boot,bootcount-device = &rv3029;
> + };
> +
> + i2c2 {
> + rv3029: rtc at 56 {
> + compatible = "mc,rv3029";
> + reg = <0x56>;
> + u-boot,bootcount-offset = <0x38>;
> + };
> + };
> +};
> +
> u-boot,spl-boot-order property
> ------------------------------
>
> diff --git a/drivers/bootcount/Kconfig b/drivers/bootcount/Kconfig
> index d335ed1..cdde7b5 100644
> --- a/drivers/bootcount/Kconfig
> +++ b/drivers/bootcount/Kconfig
> @@ -70,6 +70,18 @@ config BOOTCOUNT_AT91
> bool "Boot counter for Atmel AT91SAM9XE"
> depends on AT91SAM9XE
>
> +config BOOTCOUNT_DM
> + bool "Boot counter in a device-model device"
> + help
> + Enables reading/writing the bootcount in a device-model
> + device referenced from the /chosen node. The type of the
> + device is detected from DM and any additional configuration
> + information (e.g. the offset into a RTC device that
> supports
> + read32/write32) is read from the device's node.
> +
> + At this time the following DM device classes are supported:
> + * RTC (using read32/write32)
> +
> endchoice
>
> config BOOTCOUNT_ALEN
> diff --git a/drivers/bootcount/Makefile b/drivers/bootcount/Makefile
> index 68bc006..e8ed729 100644
> --- a/drivers/bootcount/Makefile
> +++ b/drivers/bootcount/Makefile
> @@ -7,3 +7,4 @@ obj-$(CONFIG_BOOTCOUNT_RAM) += bootcount_ram.o
> obj-$(CONFIG_BOOTCOUNT_ENV) += bootcount_env.o
> obj-$(CONFIG_BOOTCOUNT_I2C) += bootcount_i2c.o
> obj-$(CONFIG_BOOTCOUNT_EXT) += bootcount_ext.o
> +obj-$(CONFIG_BOOTCOUNT_DM) += bootcount_dm.o
> diff --git a/drivers/bootcount/bootcount_dm.c
> b/drivers/bootcount/bootcount_dm.c new file mode 100644
> index 0000000..99bdb88
> --- /dev/null
> +++ b/drivers/bootcount/bootcount_dm.c
> @@ -0,0 +1,93 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * (C) Copyright 2018 Theobroma Systems Design und Consulting GmbH
> + */
> +
> +#include <common.h>
> +#include <bootcount.h>
> +#include <dm.h>
> +#include <rtc.h>
> +
> +const u8 bootcount_magic = 0xbc;
> +
> +static void bootcount_store_rtc(struct udevice *dev, ulong a)
> +{
> +#if CONFIG_IS_ENABLED(DM_RTC)
> + u32 offset;
> + const char *offset_propname = "u-boot,bootcount-offset";
> + const u16 val = bootcount_magic << 8 | (a & 0xff);
> +
> + if (dev_read_u32(dev, offset_propname, &offset) < 0) {
> + debug("%s: requires %s\n", __func__,
> offset_propname);
> + return;
> + }
> +
> + if (rtc_write16(dev, offset, val) < 0) {
> + debug("%s: rtc_write16 failed\n", __func__);
> + return;
> + }
> +#endif
> +}
> +
> +static u32 bootcount_load_rtc(struct udevice *dev)
> +{
> +#if CONFIG_IS_ENABLED(DM_RTC)
> + u32 offset;
> + const char *offset_propname = "u-boot,bootcount-offset";
> + u16 val;
> +
> + if (dev_read_u32(dev, offset_propname, &offset) < 0) {
> + debug("%s: requires %s\n", __func__,
> offset_propname);
> + goto fail;
> + }
> +
> + if (rtc_read16(dev, offset, &val) < 0) {
> + debug("%s: rtc_write16 failed\n", __func__);
> + goto fail;
> + }
> +
> + if (val >> 8 == bootcount_magic)
> + return val & 0xff;
> +
> + debug("%s: bootcount magic does not match on %04x\n",
> __func__, val);
> + fail:
> +#endif
> + return 0;
> +}
> +
> +/* Now implement the generic default functions */
> +void bootcount_store(ulong a)
> +{
> + struct udevice *dev;
> + ofnode node;
> + const char *propname = "u-boot,bootcount-device";
> +
> + node = ofnode_get_chosen_node(propname);
> + if (!ofnode_valid(node)) {
> + debug("%s: no '%s'\n", __func__, propname);
> + return;
> + }
> +
> + /* RTC devices */
> + if (!uclass_get_device_by_ofnode(UCLASS_RTC, node, &dev))
> + return bootcount_store_rtc(dev, a);
> +}
> +
> +ulong bootcount_load(void)
> +{
> + struct udevice *dev;
> + ofnode node;
> + const char *propname = "u-boot,bootcount-device";
> +
> + node = ofnode_get_chosen_node(propname);
> + if (!ofnode_valid(node)) {
> + debug("%s: no '%s'\n", __func__, propname);
> + return 0;
> + }
> +
> + /* RTC devices */
> + if (!uclass_get_device_by_ofnode(UCLASS_RTC, node, &dev))
> + return bootcount_load_rtc(dev);
> +
> + return 0;
> +}
>
>
> Thanks for your patch.
>
> However, if I may ask - would it be possible to add support for EEPROM
> based bootcount in an easy way?
>
>
> This was always intended and is the reason why there’s a "RTC devices”
> comment in bootcount_load.
>
> If someone wants to store their bootcount in an I2C EEPROM, they just
> need to add a “uclass_get_device_by_ofnode(UCLASS_I2C_EEPROM, …)”
> with the appropriate logic in bootcount_load and bootcount_store.
>
> I mean - do you think that it would be feasible to have
> bootcount-uclass, which would support generic load/store functions with
> DM drivers for RTC, EEPROM or even simple write to SFR registers (as it
> is just an offset in the end)?
>
>
> I thought about this, but didn’t go down that route as a bootcount will
> usually
> be stored in an existing DM device (RTC, I2C-EEPROM, NOR flash). If we
> add individual bootcount-devices wrapping these, then we’d be left with the
> following in the -u-boot.dtsi:
>
> bootcount {
> compatible = “u-boot,bootcount-rtc”
> rtc = &rv3029;
> offset = <0x38>
> }
>
> While this nicely collects all the info together in one node, there’s the
> drawback
> of users that might define multiple devices and set their status to “okay”…
> which
> might cause inconsistent bootcount values across multiple devices.
>
> For this reason, I went with the other design choice of viewing the various
> bootcount
> implementations as “bootcount methods” (i.e. logic storing and retrieving a
> bootcount
> somewhere). In the case of DM backends this means that the appropriate
> method
> is to (a) identify the device by its uclass and (b) call the appropriate
> read/write method.
>
> I briefly toyed with the idea of adding infrastructure to the DM core to get
> the device
> for an ofnode (independent of its uclass) and adding a generic
> dm_read/dm_write
> that would dispatch to the appropriate uclass’ read/write after looking at
> the uclass
> of a udevice passed in. I didn’t go down that route as it seemed to
> contradict the
> architecture of DM (i.e. devices are stored in per-uclass lists) in U-Boot.
>
> One more thing that influenced the current modelling in the DTS: it prefer
> to have
> all info regarding how the SRAM in a RTC—same for the memory in an EEPROM—
> is subdivided in the RTC node. If this was in a separate node (as the
> bootcount
> node above), someone might reuse the same SRAM addresses for different
> purposes from different nodes causing inadvertent overwriting of live data.
>
>
> I have to agree with Lukasz that this should really be a uclass with a
> driver for RTC and perhaps one for EEPROM.
>
> But we also have patches roaming around for a BOARD uclass, which
> provides for reading settings from the board, which could of course
> use any kind of storage. Would that be another option?
>
>
> I’ll change this over to be a new BOOTCOUNT uclass, although my reservation
> regarding how this partitions a RTC’s or EEPROM’s address space remains.
> I guess, we’ll have to live with that.
I don't fully understand this but will await the patch for this. I'm
assuming a DT property would be needed.
>
> I don’t think this should be merged with the BOARD uclass, as the bootcount
> is a standalone feature that could be configured differently even for the
> same
> board (i.e. this is not similar enough to reading a board id to merge it
> into the
> BOARD uclass).
>
OK. I suppose the BOARD uclass could make use of a BOOTCOUNT device if needed.
Regards,
Simon
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