* [PATCH 2/3] [RFC] nvmem: syscon: Add syscon backed nvmem driver
2022-10-27 22:50 [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings Marek Vasut
@ 2022-10-27 22:50 ` Marek Vasut
2022-10-27 22:50 ` [PATCH 3/3] [RFC] ARM: dts: stm32: Add nvmem-syscon node to TAMP to expose boot count on DHSOM Marek Vasut
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Marek Vasut @ 2022-10-27 22:50 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Marek Vasut, Alexandre Torgue, Rafał Miłecki,
Rob Herring, Srinivas Kandagatla, devicetree, linux-stm32
Add trivial driver which permits exposing syscon backed register
to userspace. This is useful e.g. to expose U-Boot boot counter
on various platforms where the boot counter is stored in random
volatile register, like STM32MP15xx TAMP_BKPxR register.
Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Rafał Miłecki <rafal@milecki.pl>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: devicetree@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
---
drivers/nvmem/Kconfig | 10 ++++
drivers/nvmem/Makefile | 2 +
drivers/nvmem/nvmem-syscon.c | 105 +++++++++++++++++++++++++++++++++++
3 files changed, 117 insertions(+)
create mode 100644 drivers/nvmem/nvmem-syscon.c
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index ec8a49c040031..cd9a7b00bc1ab 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -290,6 +290,16 @@ config NVMEM_SPRD_EFUSE
This driver can also be built as a module. If so, the module
will be called nvmem-sprd-efuse.
+config NVMEM_SYSCON
+ tristate "Generic syscon backed nvmem"
+ help
+ This is a driver for generic syscon backed nvmem. This can be
+ used to expose arbitrary syscon backed register to user space
+ via nvmem, like the U-Boot boot counter.
+
+ This driver can also be built as a module. If so, the module
+ will be called nvmem-syscon.
+
config NVMEM_STM32_ROMEM
tristate "STMicroelectronics STM32 factory-programmed memory support"
depends on ARCH_STM32 || COMPILE_TEST
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index fa80fe17e567e..6e170b30a1d1d 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -59,6 +59,8 @@ obj-$(CONFIG_NVMEM_SPMI_SDAM) += nvmem_qcom-spmi-sdam.o
nvmem_qcom-spmi-sdam-y += qcom-spmi-sdam.o
obj-$(CONFIG_NVMEM_SPRD_EFUSE) += nvmem_sprd_efuse.o
nvmem_sprd_efuse-y := sprd-efuse.o
+obj-$(CONFIG_NVMEM_SYSCON) += nvmem_syscon.o
+nvmem_syscon-y := nvmem-syscon.o
obj-$(CONFIG_NVMEM_STM32_ROMEM) += nvmem_stm32_romem.o
nvmem_stm32_romem-y := stm32-romem.o
obj-$(CONFIG_NVMEM_SUNPLUS_OCOTP) += nvmem_sunplus_ocotp.o
diff --git a/drivers/nvmem/nvmem-syscon.c b/drivers/nvmem/nvmem-syscon.c
new file mode 100644
index 0000000000000..9a7f9a5e37609
--- /dev/null
+++ b/drivers/nvmem/nvmem-syscon.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Marek Vasut <marex@denx.de>
+ *
+ * Based on snvs_lpgpr.c .
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+
+struct nvmem_syscon_priv {
+ struct device_d *dev;
+ struct regmap *regmap;
+ struct nvmem_config cfg;
+ unsigned int off;
+};
+
+static int nvmem_syscon_write(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct nvmem_syscon_priv *priv = context;
+
+ return regmap_bulk_write(priv->regmap, priv->off + offset,
+ val, bytes / 4);
+}
+
+static int nvmem_syscon_read(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct nvmem_syscon_priv *priv = context;
+
+ return regmap_bulk_read(priv->regmap, priv->off + offset,
+ val, bytes / 4);
+}
+
+static int nvmem_syscon_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = dev->of_node;
+ struct device_node *syscon_node;
+ struct nvmem_syscon_priv *priv;
+ struct nvmem_device *nvmem;
+ struct nvmem_config *cfg;
+ int ret;
+
+ if (!node)
+ return -ENOENT;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ ret = of_property_read_u32_index(node, "reg", 0, &priv->off);
+ if (ret)
+ return ret;
+
+ ret = of_property_read_u32_index(node, "reg", 1, &priv->cfg.size);
+ if (ret)
+ return ret;
+
+ syscon_node = of_get_parent(node);
+ if (!syscon_node)
+ return -ENODEV;
+
+ priv->regmap = syscon_node_to_regmap(syscon_node);
+ of_node_put(syscon_node);
+ if (IS_ERR(priv->regmap))
+ return PTR_ERR(priv->regmap);
+
+ cfg = &priv->cfg;
+ cfg->priv = priv;
+ cfg->name = dev_name(dev);
+ cfg->dev = dev;
+ cfg->stride = 4;
+ cfg->word_size = 4;
+ cfg->owner = THIS_MODULE;
+ cfg->reg_read = nvmem_syscon_read;
+ cfg->reg_write = nvmem_syscon_write;
+
+ nvmem = devm_nvmem_register(dev, cfg);
+
+ return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id nvmem_syscon_dt_ids[] = {
+ { .compatible = "nvmem-syscon" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, nvmem_syscon_dt_ids);
+
+static struct platform_driver nvmem_syscon_driver = {
+ .probe = nvmem_syscon_probe,
+ .driver = {
+ .name = "nvmem-syscon",
+ .of_match_table = nvmem_syscon_dt_ids,
+ },
+};
+module_platform_driver(nvmem_syscon_driver);
+
+MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
+MODULE_DESCRIPTION("Generic syscon nvmem driver");
+MODULE_LICENSE("GPL");
--
2.35.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 3/3] [RFC] ARM: dts: stm32: Add nvmem-syscon node to TAMP to expose boot count on DHSOM
2022-10-27 22:50 [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings Marek Vasut
2022-10-27 22:50 ` [PATCH 2/3] [RFC] nvmem: syscon: Add syscon backed nvmem driver Marek Vasut
@ 2022-10-27 22:50 ` Marek Vasut
2022-10-28 12:20 ` [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings Rob Herring
2022-10-28 21:28 ` Rob Herring
3 siblings, 0 replies; 6+ messages in thread
From: Marek Vasut @ 2022-10-27 22:50 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Marek Vasut, Alexandre Torgue, Rafał Miłecki,
Rob Herring, Srinivas Kandagatla, devicetree, linux-stm32
Add nvmem-syscon subnode to expose TAMP_BKPxR register 19 to user space.
This register contains U-Boot boot counter, by exposing it to user space
the user space can reset the boot counter.
Read access example:
"
$ hexdump -vC /sys/bus/nvmem/devices/5c00a000.tamp\:nvmem0/nvmem
00000000 0c 00 c4 b0
"
Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Rafał Miłecki <rafal@milecki.pl>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: devicetree@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
---
arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi | 11 +++++++++++
arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi | 11 +++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi b/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
index 155843e1402fb..8277837be8a51 100644
--- a/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
+++ b/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
@@ -533,6 +533,17 @@ &sdmmc3 {
status = "okay";
};
+&tamp {
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ /* Boot counter */
+ nvmem {
+ compatible = "nvmem-syscon";
+ reg = <0x14c 0x4>;
+ };
+};
+
&uart4 {
pinctrl-names = "default";
pinctrl-0 = <&uart4_pins_a>;
diff --git a/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi b/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
index 134a798ad3f23..42a8d5cdd7024 100644
--- a/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
+++ b/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
@@ -271,3 +271,14 @@ &rng1 {
&rtc {
status = "okay";
};
+
+&tamp {
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ /* Boot counter */
+ nvmem {
+ compatible = "nvmem-syscon";
+ reg = <0x14c 0x4>;
+ };
+};
--
2.35.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings
2022-10-27 22:50 [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings Marek Vasut
2022-10-27 22:50 ` [PATCH 2/3] [RFC] nvmem: syscon: Add syscon backed nvmem driver Marek Vasut
2022-10-27 22:50 ` [PATCH 3/3] [RFC] ARM: dts: stm32: Add nvmem-syscon node to TAMP to expose boot count on DHSOM Marek Vasut
@ 2022-10-28 12:20 ` Rob Herring
2022-10-28 21:28 ` Rob Herring
3 siblings, 0 replies; 6+ messages in thread
From: Rob Herring @ 2022-10-28 12:20 UTC (permalink / raw)
To: Marek Vasut
Cc: Rafał Miłecki, linux-stm32, Srinivas Kandagatla,
linux-arm-kernel, Alexandre Torgue, devicetree, Rob Herring
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 3363 bytes --]
On Fri, 28 Oct 2022 00:50:18 +0200, Marek Vasut wrote:
> Add trivial bindings for driver which permits exposing syscon backed
> register to userspace. This is useful e.g. to expose U-Boot boot
> counter on various platforms where the boot counter is stored in
> random volatile register, like STM32MP15xx TAMP_BKPxR register.
>
> Signed-off-by: Marek Vasut <marex@denx.de>
> ---
> Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
> Cc: Rafał Miłecki <rafal@milecki.pl>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> Cc: devicetree@vger.kernel.org
> Cc: linux-stm32@st-md-mailman.stormreply.com
> To: linux-arm-kernel@lists.infradead.org
> ---
> .../bindings/nvmem/nvmem-syscon.yaml | 39 +++++++++++++++++++
> 1 file changed, 39 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
>
My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
on your patch (DT_CHECKER_FLAGS is new in v5.13):
yamllint warnings/errors:
dtschema/dtc warnings/errors:
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dts:24.17-35: Warning (reg_format): /example-0/tamp@5c00a000/nvmem-syscon:reg: property has invalid length (8 bytes) (#address-cells == 2, #size-cells == 1)
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dts:22.26-25.15: Warning (unit_address_vs_reg): /example-0/tamp@5c00a000/nvmem-syscon: node has a reg or ranges property, but no unit name
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: Warning (pci_device_reg): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: Warning (pci_device_bus_num): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: Warning (simple_bus_reg): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: Warning (i2c_bus_reg): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: Warning (spi_bus_reg): Failed prerequisite 'reg_format'
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dts:22.26-25.15: Warning (avoid_default_addr_size): /example-0/tamp@5c00a000/nvmem-syscon: Relying on default #address-cells value
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dts:22.26-25.15: Warning (avoid_default_addr_size): /example-0/tamp@5c00a000/nvmem-syscon: Relying on default #size-cells value
Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: Warning (unique_unit_address_if_enabled): Failed prerequisite 'avoid_default_addr_size'
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/nvmem/nvmem-syscon.example.dtb: tamp@5c00a000: 'nvmem-syscon' does not match any of the regexes: 'pinctrl-[0-9]+'
From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/arm/stm32/st,stm32-syscon.yaml
doc reference errors (make refcheckdocs):
See https://patchwork.ozlabs.org/patch/
This check can fail if there are any dependencies. The base for a patch
series is generally the most recent rc1.
If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:
pip3 install dtschema --upgrade
Please check and re-submit.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings
2022-10-27 22:50 [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings Marek Vasut
` (2 preceding siblings ...)
2022-10-28 12:20 ` [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings Rob Herring
@ 2022-10-28 21:28 ` Rob Herring
2022-11-27 22:05 ` Marek Vasut
3 siblings, 1 reply; 6+ messages in thread
From: Rob Herring @ 2022-10-28 21:28 UTC (permalink / raw)
To: Marek Vasut
Cc: linux-arm-kernel, Alexandre Torgue, Rafał Miłecki,
Srinivas Kandagatla, devicetree, linux-stm32
On Fri, Oct 28, 2022 at 12:50:18AM +0200, Marek Vasut wrote:
> Add trivial bindings for driver which permits exposing syscon backed
> register to userspace. This is useful e.g. to expose U-Boot boot
> counter on various platforms where the boot counter is stored in
> random volatile register, like STM32MP15xx TAMP_BKPxR register.
Generic bindings always start trivial until they get appended one
property at a time...
What happens when you have more than 1 field and/or more than 1
register?
> Signed-off-by: Marek Vasut <marex@denx.de>
> ---
> Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
> Cc: Rafał Miłecki <rafal@milecki.pl>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> Cc: devicetree@vger.kernel.org
> Cc: linux-stm32@st-md-mailman.stormreply.com
> To: linux-arm-kernel@lists.infradead.org
> ---
> .../bindings/nvmem/nvmem-syscon.yaml | 39 +++++++++++++++++++
> 1 file changed, 39 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
>
> diff --git a/Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml b/Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
> new file mode 100644
> index 0000000000000..3035a0b2cd24a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/nvmem-syscon.yaml
> @@ -0,0 +1,39 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/nvmem/nvmem-syscon.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic syscon backed nvmem
> +
> +maintainers:
> + - Marek Vasut <marex@denx.de>
> +
> +allOf:
> + - $ref: "nvmem.yaml#"
> +
> +properties:
> + compatible:
> + enum:
> + - nvmem-syscon
> +
> + reg:
> + maxItems: 1
> +
> +required:
> + - compatible
> + - reg
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + tamp@5c00a000 {
> + compatible = "st,stm32-tamp", "syscon", "simple-mfd";
This is very common, but personally I think "syscon" and "simple-mfd"
should be mutually exclusive. "simple-mfd" is saying the children have
no dependency on the parent, yet the child nodes need a regmap from the
parent. Sounds like a dependency.
> + reg = <0x5c00a000 0x400>;
> +
> + nvmem-syscon {
> + compatible = "nvmem-syscon";
> + reg = <0x14c 0x4>;
How does one identify this is the bootloader's boot count? How does the
bootloader know it can write to this?
> + };
> + };
> --
> 2.35.1
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/3] [RFC] dt-bindings: nvmem: syscon: Add syscon backed nvmem bindings
2022-10-28 21:28 ` Rob Herring
@ 2022-11-27 22:05 ` Marek Vasut
0 siblings, 0 replies; 6+ messages in thread
From: Marek Vasut @ 2022-11-27 22:05 UTC (permalink / raw)
To: Rob Herring
Cc: linux-arm-kernel, Alexandre Torgue, Rafał Miłecki,
Srinivas Kandagatla, devicetree, linux-stm32
On 10/28/22 23:28, Rob Herring wrote:
> On Fri, Oct 28, 2022 at 12:50:18AM +0200, Marek Vasut wrote:
>> Add trivial bindings for driver which permits exposing syscon backed
>> register to userspace. This is useful e.g. to expose U-Boot boot
>> counter on various platforms where the boot counter is stored in
>> random volatile register, like STM32MP15xx TAMP_BKPxR register.
>
> Generic bindings always start trivial until they get appended one
> property at a time...
>
> What happens when you have more than 1 field and/or more than 1
> register?
If it is a continuous register array, the user can use the size field to
describe such register array here.
If it is a sparse register array, multiple nvmem-syscon nodes would be
needed. I haven't seen anything which would require one node for sparse
register arrays, like boot counter distributed across multiple
non-continuous registers or such.
>> +properties:
>> + compatible:
>> + enum:
>> + - nvmem-syscon
>> +
>> + reg:
>> + maxItems: 1
>> +
>> +required:
>> + - compatible
>> + - reg
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> + - |
>> + tamp@5c00a000 {
>> + compatible = "st,stm32-tamp", "syscon", "simple-mfd";
>
> This is very common, but personally I think "syscon" and "simple-mfd"
> should be mutually exclusive. "simple-mfd" is saying the children have
> no dependency on the parent, yet the child nodes need a regmap from the
> parent. Sounds like a dependency.
So what exactly should be changed here?
>> + reg = <0x5c00a000 0x400>;
>> +
>> + nvmem-syscon {
>> + compatible = "nvmem-syscon";
>> + reg = <0x14c 0x4>;
>
> How does one identify this is the bootloader's boot count?
The user has to know where the boot counter is stored (by hardware
path). I wouldn't attempt to assign any complex logic here, since the
boot counter could be implemented in various ways. Besides, this may not
even be a boot counter, but some other variable exposed to user space.
Maybe a unique node name can be used to discern the different
nvmem-syscon nodes representing different variables if needed.
> How does the
> bootloader know it can write to this?
The bootloader implementer selected the bootcounter register based on
hardware knowledge .
^ permalink raw reply [flat|nested] 6+ messages in thread