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

[Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>]

On 09/03/2023 11:20, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@xxxxxxxxxx>
>
> 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)

Am really not sure what is going on here,
I did raise some issues with this overall approch to start with at [1] 
none of which are discussed and now I see v3 :-)

[1] 
https://lore.kernel.org/lkml/20230309094010.1051573-1-michael@xxxxxxxx/T/#m7706b640979aabf251436e017b8189413661a53a

--srini
> 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@xxxxxxxxxx>
> [for meson-{efuse,mx-efuse}.c]
> Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> [for mtk-efuse.c, nvmem/core.c, nvmem-provider.h]
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> [MT8192, MT8195 Chromebooks]
> Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> [for microchip-otpc.c]
> Reviewed-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
> [SAMA7G5-EK]
> Tested-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
> ---
> 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;