[PATCH V3] nvmem: add explicit config option to read OF fixed cells

Rafał Miłecki zajec5 at gmail.com
Thu Mar 9 03:20:28 PST 2023 

From: Rafał Miłecki <rafal at milecki.pl>

NVMEM subsystem looks for fixed NVMEM cells (specified in DT) by
default. This behaviour was totally safe in early days before adding
support for dynamic cells and with simple DT syntax.

With every new supported NVMEM device with dynamic cells the current
behaviour becomes non-optimal:
1. It results in unneeded iterating over DT nodes
2. It may result in false discovery of cells (in case DT subnodes
   contain "reg" property)

This behaviour has actually caused a problem already with the MTD
subsystem and required a fix. MTD subpartitions were incorrectly treated
(falsely discovered) as NVMEM cells.

Also with the support for NVMEM layouts we may & should have *new*
bindings allow fixed NVMEM cells only in the "nvmem-layout" subnode. It
means no *new* driver should require NVMEM core support for fixed cells
defined in the **device** node.

Obviously existing bindings must be supported and old drivers must
support old DT syntax.

The best approach seems to be making NVMEM core looking for fixed DT
cells in **device** node an opt-in feature. It's a feature that over
time should get deprecated in a favor of using "nvmem-layouts" also for
fixed NVMEM cells.

Solve this by modifying drivers for those bindings that support
specifying fixed NVMEM cells in DT node of **NVMEM device**. Those
drivers were picked by reviewing all supported NVMEM bindings. Make
those drivers explicitly tell NVMEM subsystem to read cells from DT node
of **NVMEM device**.

It wasn't clear (to me) if rtc and w1 code actually uses fixed cells. I
enabled them to don't risk any breakage.

The whole change is not a huge game changer. It makes code slightly more
optimal (in case you care), a bit less error prone and maybe / hopefully
NVMEM code parsing code easier to understand.

Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
[for meson-{efuse,mx-efuse}.c]
Acked-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
[for mtk-efuse.c, nvmem/core.c, nvmem-provider.h]
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
[MT8192, MT8195 Chromebooks]
Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
[for microchip-otpc.c]
Reviewed-by: Claudiu Beznea <claudiu.beznea at microchip.com>
[SAMA7G5-EK]
Tested-by: Claudiu Beznea <claudiu.beznea at microchip.com>
---
V2: Fix stm32-romem.c typo breaking its compilation
    Pick Martin's Acked-by
    Add paragraph about layouts deprecating use_fixed_of_cells
V3: Update commit description:
    1. Make it clear we're NOT dropping fixed cells support
    2. Use nicer words (s/made sense/was totally safe/)
    3. Explain fixed cells layout thing
    4. Add paragraph with purpose of this commit
---
 drivers/mtd/mtdcore.c          | 2 ++
 drivers/nvmem/apple-efuses.c   | 1 +
 drivers/nvmem/core.c           | 8 +++++---
 drivers/nvmem/imx-ocotp-scu.c  | 1 +
 drivers/nvmem/imx-ocotp.c      | 1 +
 drivers/nvmem/meson-efuse.c    | 1 +
 drivers/nvmem/meson-mx-efuse.c | 1 +
 drivers/nvmem/microchip-otpc.c | 1 +
 drivers/nvmem/mtk-efuse.c      | 1 +
 drivers/nvmem/qcom-spmi-sdam.c | 1 +
 drivers/nvmem/qfprom.c         | 1 +
 drivers/nvmem/rave-sp-eeprom.c | 1 +
 drivers/nvmem/rockchip-efuse.c | 1 +
 drivers/nvmem/sc27xx-efuse.c   | 1 +
 drivers/nvmem/sprd-efuse.c     | 1 +
 drivers/nvmem/stm32-romem.c    | 1 +
 drivers/nvmem/sunplus-ocotp.c  | 1 +
 drivers/nvmem/sunxi_sid.c      | 1 +
 drivers/nvmem/uniphier-efuse.c | 1 +
 drivers/nvmem/zynqmp_nvmem.c   | 1 +
 drivers/rtc/nvmem.c            | 1 +
 drivers/w1/slaves/w1_ds250x.c  | 1 +
 include/linux/nvmem-provider.h | 2 ++
 23 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 0feacb9fbdac..1bb479c0f758 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -523,6 +523,7 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
 	config.dev = &mtd->dev;
 	config.name = dev_name(&mtd->dev);
 	config.owner = THIS_MODULE;
+	config.use_fixed_of_cells = of_device_is_compatible(node, "nvmem-cells");
 	config.reg_read = mtd_nvmem_reg_read;
 	config.size = mtd->size;
 	config.word_size = 1;
@@ -891,6 +892,7 @@ static struct nvmem_device *mtd_otp_nvmem_register(struct mtd_info *mtd,
 	config.name = kasprintf(GFP_KERNEL, "%s-%s", dev_name(&mtd->dev), compatible);
 	config.id = NVMEM_DEVID_NONE;
 	config.owner = THIS_MODULE;
+	config.use_fixed_of_cells = true;
 	config.type = NVMEM_TYPE_OTP;
 	config.root_only = true;
 	config.ignore_wp = true;
diff --git a/drivers/nvmem/apple-efuses.c b/drivers/nvmem/apple-efuses.c
index 9b7c87102104..0119bac43b2c 100644
--- a/drivers/nvmem/apple-efuses.c
+++ b/drivers/nvmem/apple-efuses.c
@@ -36,6 +36,7 @@ static int apple_efuses_probe(struct platform_device *pdev)
 	struct resource *res;
 	struct nvmem_config config = {
 		.dev = &pdev->dev,
+		.use_fixed_of_cells = true,
 		.read_only = true,
 		.reg_read = apple_efuses_read,
 		.stride = sizeof(u32),
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 174ef3574e07..6783cd8478d7 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -844,9 +844,11 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 	if (rval)
 		goto err_remove_cells;
 
-	rval = nvmem_add_cells_from_of(nvmem);
-	if (rval)
-		goto err_remove_cells;
+	if (config->use_fixed_of_cells) {
+		rval = nvmem_add_cells_from_of(nvmem);
+		if (rval)
+			goto err_remove_cells;
+	}
 
 	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
 
diff --git a/drivers/nvmem/imx-ocotp-scu.c b/drivers/nvmem/imx-ocotp-scu.c
index 399e1eb8b4c1..ec5cce7c6697 100644
--- a/drivers/nvmem/imx-ocotp-scu.c
+++ b/drivers/nvmem/imx-ocotp-scu.c
@@ -220,6 +220,7 @@ static int imx_scu_ocotp_write(void *context, unsigned int offset,
 
 static struct nvmem_config imx_scu_ocotp_nvmem_config = {
 	.name = "imx-scu-ocotp",
+	.use_fixed_of_cells = true,
 	.read_only = false,
 	.word_size = 4,
 	.stride = 1,
diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index e9b52ecb3f72..e37a82f98ba6 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -616,6 +616,7 @@ static int imx_ocotp_probe(struct platform_device *pdev)
 		return PTR_ERR(priv->clk);
 
 	priv->params = of_device_get_match_data(&pdev->dev);
+	imx_ocotp_nvmem_config.use_fixed_of_cells = true;
 	imx_ocotp_nvmem_config.size = 4 * priv->params->nregs;
 	imx_ocotp_nvmem_config.dev = dev;
 	imx_ocotp_nvmem_config.priv = priv;
diff --git a/drivers/nvmem/meson-efuse.c b/drivers/nvmem/meson-efuse.c
index d6b533497ce1..657e171d5af3 100644
--- a/drivers/nvmem/meson-efuse.c
+++ b/drivers/nvmem/meson-efuse.c
@@ -93,6 +93,7 @@ static int meson_efuse_probe(struct platform_device *pdev)
 
 	econfig->dev = dev;
 	econfig->name = dev_name(dev);
+	econfig->use_fixed_of_cells = true;
 	econfig->stride = 1;
 	econfig->word_size = 1;
 	econfig->reg_read = meson_efuse_read;
diff --git a/drivers/nvmem/meson-mx-efuse.c b/drivers/nvmem/meson-mx-efuse.c
index 13eb14316f46..7cc51391ec9c 100644
--- a/drivers/nvmem/meson-mx-efuse.c
+++ b/drivers/nvmem/meson-mx-efuse.c
@@ -213,6 +213,7 @@ static int meson_mx_efuse_probe(struct platform_device *pdev)
 	efuse->config.owner = THIS_MODULE;
 	efuse->config.dev = &pdev->dev;
 	efuse->config.priv = efuse;
+	efuse->config.use_fixed_of_cells = true;
 	efuse->config.stride = drvdata->word_size;
 	efuse->config.word_size = drvdata->word_size;
 	efuse->config.size = SZ_512;
diff --git a/drivers/nvmem/microchip-otpc.c b/drivers/nvmem/microchip-otpc.c
index 436e0dc4f337..fb920fd7a8fc 100644
--- a/drivers/nvmem/microchip-otpc.c
+++ b/drivers/nvmem/microchip-otpc.c
@@ -261,6 +261,7 @@ static int mchp_otpc_probe(struct platform_device *pdev)
 		return ret;
 
 	mchp_nvmem_config.dev = otpc->dev;
+	mchp_nvmem_config.use_fixed_of_cells = true;
 	mchp_nvmem_config.size = size;
 	mchp_nvmem_config.priv = otpc;
 	nvmem = devm_nvmem_register(&pdev->dev, &mchp_nvmem_config);
diff --git a/drivers/nvmem/mtk-efuse.c b/drivers/nvmem/mtk-efuse.c
index a08e0aedd21c..1947337a121f 100644
--- a/drivers/nvmem/mtk-efuse.c
+++ b/drivers/nvmem/mtk-efuse.c
@@ -45,6 +45,7 @@ static int mtk_efuse_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->base))
 		return PTR_ERR(priv->base);
 
+	econfig.use_fixed_of_cells = true;
 	econfig.stride = 1;
 	econfig.word_size = 1;
 	econfig.reg_read = mtk_reg_read;
diff --git a/drivers/nvmem/qcom-spmi-sdam.c b/drivers/nvmem/qcom-spmi-sdam.c
index f822790db49e..b547def94b5b 100644
--- a/drivers/nvmem/qcom-spmi-sdam.c
+++ b/drivers/nvmem/qcom-spmi-sdam.c
@@ -142,6 +142,7 @@ static int sdam_probe(struct platform_device *pdev)
 	sdam->sdam_config.name = "spmi_sdam";
 	sdam->sdam_config.id = NVMEM_DEVID_AUTO;
 	sdam->sdam_config.owner = THIS_MODULE;
+	sdam->sdam_config.use_fixed_of_cells = true;
 	sdam->sdam_config.stride = 1;
 	sdam->sdam_config.word_size = 1;
 	sdam->sdam_config.reg_read = sdam_read;
diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index c1e893c8a247..eb126d507561 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c
@@ -357,6 +357,7 @@ static int qfprom_probe(struct platform_device *pdev)
 {
 	struct nvmem_config econfig = {
 		.name = "qfprom",
+		.use_fixed_of_cells = true,
 		.stride = 1,
 		.word_size = 1,
 		.id = NVMEM_DEVID_AUTO,
diff --git a/drivers/nvmem/rave-sp-eeprom.c b/drivers/nvmem/rave-sp-eeprom.c
index c456011b75e8..e9b4c7927e37 100644
--- a/drivers/nvmem/rave-sp-eeprom.c
+++ b/drivers/nvmem/rave-sp-eeprom.c
@@ -328,6 +328,7 @@ static int rave_sp_eeprom_probe(struct platform_device *pdev)
 	of_property_read_string(np, "zii,eeprom-name", &config.name);
 	config.priv		= eeprom;
 	config.dev		= dev;
+	config.use_fixed_of_cells	= true;
 	config.size		= size;
 	config.reg_read		= rave_sp_eeprom_reg_read;
 	config.reg_write	= rave_sp_eeprom_reg_write;
diff --git a/drivers/nvmem/rockchip-efuse.c b/drivers/nvmem/rockchip-efuse.c
index e4579de5d014..211f6e7401a9 100644
--- a/drivers/nvmem/rockchip-efuse.c
+++ b/drivers/nvmem/rockchip-efuse.c
@@ -205,6 +205,7 @@ static int rockchip_rk3399_efuse_read(void *context, unsigned int offset,
 
 static struct nvmem_config econfig = {
 	.name = "rockchip-efuse",
+	.use_fixed_of_cells = true,
 	.stride = 1,
 	.word_size = 1,
 	.read_only = true,
diff --git a/drivers/nvmem/sc27xx-efuse.c b/drivers/nvmem/sc27xx-efuse.c
index c825fc902d10..ed5cc4f3e2bc 100644
--- a/drivers/nvmem/sc27xx-efuse.c
+++ b/drivers/nvmem/sc27xx-efuse.c
@@ -248,6 +248,7 @@ static int sc27xx_efuse_probe(struct platform_device *pdev)
 	econfig.reg_read = sc27xx_efuse_read;
 	econfig.priv = efuse;
 	econfig.dev = &pdev->dev;
+	econfig.use_fixed_of_cells = true;
 	nvmem = devm_nvmem_register(&pdev->dev, &econfig);
 	if (IS_ERR(nvmem)) {
 		dev_err(&pdev->dev, "failed to register nvmem config\n");
diff --git a/drivers/nvmem/sprd-efuse.c b/drivers/nvmem/sprd-efuse.c
index 4f1fcbfec394..ef3161645f60 100644
--- a/drivers/nvmem/sprd-efuse.c
+++ b/drivers/nvmem/sprd-efuse.c
@@ -408,6 +408,7 @@ static int sprd_efuse_probe(struct platform_device *pdev)
 	econfig.read_only = false;
 	econfig.name = "sprd-efuse";
 	econfig.size = efuse->data->blk_nums * SPRD_EFUSE_BLOCK_WIDTH;
+	econfig.use_fixed_of_cells = true;
 	econfig.reg_read = sprd_efuse_read;
 	econfig.reg_write = sprd_efuse_write;
 	econfig.priv = efuse;
diff --git a/drivers/nvmem/stm32-romem.c b/drivers/nvmem/stm32-romem.c
index ba779e26937a..a6fc43acb797 100644
--- a/drivers/nvmem/stm32-romem.c
+++ b/drivers/nvmem/stm32-romem.c
@@ -208,6 +208,7 @@ static int stm32_romem_probe(struct platform_device *pdev)
 	priv->cfg.priv = priv;
 	priv->cfg.owner = THIS_MODULE;
 	priv->cfg.type = NVMEM_TYPE_OTP;
+	priv->cfg.use_fixed_of_cells = true;
 
 	priv->lower = 0;
 
diff --git a/drivers/nvmem/sunplus-ocotp.c b/drivers/nvmem/sunplus-ocotp.c
index 52b928a7a6d5..57e3e0833b85 100644
--- a/drivers/nvmem/sunplus-ocotp.c
+++ b/drivers/nvmem/sunplus-ocotp.c
@@ -145,6 +145,7 @@ static int sp_ocotp_read(void *priv, unsigned int offset, void *value, size_t by
 
 static struct nvmem_config sp_ocotp_nvmem_config = {
 	.name = "sp-ocotp",
+	.use_fixed_of_cells = true,
 	.read_only = true,
 	.word_size = 1,
 	.size = QAC628_OTP_SIZE,
diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c
index a970f1741cc6..6ab7aa3724a0 100644
--- a/drivers/nvmem/sunxi_sid.c
+++ b/drivers/nvmem/sunxi_sid.c
@@ -156,6 +156,7 @@ static int sunxi_sid_probe(struct platform_device *pdev)
 	nvmem_cfg->dev = dev;
 	nvmem_cfg->name = "sunxi-sid";
 	nvmem_cfg->type = NVMEM_TYPE_OTP;
+	nvmem_cfg->use_fixed_of_cells = true;
 	nvmem_cfg->read_only = true;
 	nvmem_cfg->size = cfg->size;
 	nvmem_cfg->word_size = 1;
diff --git a/drivers/nvmem/uniphier-efuse.c b/drivers/nvmem/uniphier-efuse.c
index aca910b3b6f8..69b9dfe6ab6e 100644
--- a/drivers/nvmem/uniphier-efuse.c
+++ b/drivers/nvmem/uniphier-efuse.c
@@ -53,6 +53,7 @@ static int uniphier_efuse_probe(struct platform_device *pdev)
 	econfig.size = resource_size(res);
 	econfig.priv = priv;
 	econfig.dev = dev;
+	econfig.use_fixed_of_cells = true;
 	nvmem = devm_nvmem_register(dev, &econfig);
 
 	return PTR_ERR_OR_ZERO(nvmem);
diff --git a/drivers/nvmem/zynqmp_nvmem.c b/drivers/nvmem/zynqmp_nvmem.c
index e28d7b133e11..d13750a4c112 100644
--- a/drivers/nvmem/zynqmp_nvmem.c
+++ b/drivers/nvmem/zynqmp_nvmem.c
@@ -58,6 +58,7 @@ static int zynqmp_nvmem_probe(struct platform_device *pdev)
 
 	priv->dev = dev;
 	econfig.dev = dev;
+	econfig.use_fixed_of_cells = true;
 	econfig.reg_read = zynqmp_nvmem_read;
 	econfig.priv = priv;
 
diff --git a/drivers/rtc/nvmem.c b/drivers/rtc/nvmem.c
index 07ede21cee34..5cc039d92257 100644
--- a/drivers/rtc/nvmem.c
+++ b/drivers/rtc/nvmem.c
@@ -21,6 +21,7 @@ int devm_rtc_nvmem_register(struct rtc_device *rtc,
 
 	nvmem_config->dev = dev;
 	nvmem_config->owner = rtc->owner;
+	nvmem_config->use_fixed_of_cells = true;
 	nvmem = devm_nvmem_register(dev, nvmem_config);
 	if (IS_ERR(nvmem))
 		dev_err(dev, "failed to register nvmem device for RTC\n");
diff --git a/drivers/w1/slaves/w1_ds250x.c b/drivers/w1/slaves/w1_ds250x.c
index 7592c7050d1d..538722b41f87 100644
--- a/drivers/w1/slaves/w1_ds250x.c
+++ b/drivers/w1/slaves/w1_ds250x.c
@@ -168,6 +168,7 @@ static int w1_eprom_add_slave(struct w1_slave *sl)
 	struct nvmem_device *nvmem;
 	struct nvmem_config nvmem_cfg = {
 		.dev = &sl->dev,
+		.use_fixed_of_cells = true,
 		.reg_read = w1_nvmem_read,
 		.type = NVMEM_TYPE_OTP,
 		.read_only = true,
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index 0262b86194eb..b3c14ce87a65 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -73,6 +73,7 @@ struct nvmem_cell_info {
  * @owner:	Pointer to exporter module. Used for refcounting.
  * @cells:	Optional array of pre-defined NVMEM cells.
  * @ncells:	Number of elements in cells.
+ * @use_fixed_of_cells:	Read fixed NVMEM cells from OF.
  * @keepout:	Optional array of keepout ranges (sorted ascending by start).
  * @nkeepout:	Number of elements in the keepout array.
  * @type:	Type of the nvmem storage
@@ -103,6 +104,7 @@ struct nvmem_config {
 	struct module		*owner;
 	const struct nvmem_cell_info	*cells;
 	int			ncells;
+	bool			use_fixed_of_cells;
 	const struct nvmem_keepout *keepout;
 	unsigned int		nkeepout;
 	enum nvmem_type		type;
-- 
2.34.1

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