Date: Mon, 6 Jul 2015 12:16:34 +0200 (CEST)
From: Stefan Wahren <stefan.wahren@i2se.com>
Reply-To: Stefan Wahren <stefan.wahren@i2se.com>
To: Sanchayan Maity <maitysanchayan@gmail.com>,
        linux-arm-kernel@lists.infradead.org
Cc: stefan@agner.ch, srinivas.kandagatla@linaro.org, kernel@pengutronix.de,
        linux-kernel@vger.kernel.org, shawn.guo@linaro.org,
        maxime.ripard@free-electrons.com
Message-ID: <1877493336.206622.1436177794342.JavaMail.open-xchange@oxbsltgw01.schlund.de>
In-Reply-To: <9593ca1f925aff20a6671262efd2f45e256ea676.1435574288.git.maitysanchayan@gmail.com>
References: <cover.1435574288.git.maitysanchayan@gmail.com> <9593ca1f925aff20a6671262efd2f45e256ea676.1435574288.git.maitysanchayan@gmail.com>
Subject: Re: [RFC PATCH v6 3/3] drivers: nvmem: Add Vybrid OCOTP support
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Hi Sanchayan,

> Sanchayan Maity <maitysanchayan@gmail.com> hat am 29. Juni 2015 um 13:22
> geschrieben:
>
>
> The patch adds support for the On Chip One Time Programmable Peripheral
> (OCOTP) on the Vybrid platform.

please provide a changelog in your cover letter and a new version after changes.

I think it's important to note that the driver only support read-only access.

>
> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
> ---
> drivers/nvmem/Kconfig | 10 ++
> drivers/nvmem/Makefile | 2 +
> drivers/nvmem/vf610-ocotp.c | 250 ++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 262 insertions(+)
> create mode 100644 drivers/nvmem/vf610-ocotp.c
>
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index 17f1a57..84c830d 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -33,4 +33,14 @@ config NVMEM_SUNXI_SID
> This driver can also be built as a module. If so, the module
> will be called eeprom-sunxi-sid.
>
> +config NVMEM_VF610_OCOTP
> + tristate "VF610 SoCs OCOTP support"
> + depends on SOC_VF610
> + help
> + This is a driver for the 'OCOTP' available on various Vybrid
> + devices.

I don't know much about Vybrid. But this driver is specific for VF610, isn't it?

> +
> + This driver can also be built as a module. If so, the module
> + will be called nvmem-vf610-ocotp.
> +
> endif
> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> index cc46791..a9ed113 100644
> --- a/drivers/nvmem/Makefile
> +++ b/drivers/nvmem/Makefile
> @@ -11,3 +11,5 @@ obj-$(CONFIG_QCOM_QFPROM) += nvmem_qfprom.o
> nvmem_qfprom-y := qfprom.o
> obj-$(CONFIG_NVMEM_SUNXI_SID) += nvmem-sunxi-sid.o
> nvmem-sunxi-sid-y := sunxi-sid.o
> +obj-$(CONFIG_NVMEM_VF610_OCOTP) += nvmem-vf610-ocotp.o
> +nvmem-vf610-ocotp-y := vf610-ocotp.o
> diff --git a/drivers/nvmem/vf610-ocotp.c b/drivers/nvmem/vf610-ocotp.c
> new file mode 100644
> index 0000000..b7a782c
> --- /dev/null
> +++ b/drivers/nvmem/vf610-ocotp.c
> @@ -0,0 +1,250 @@
> +/*
> + * Copyright (C) 2015 Sanchayan Maity <sanchayan.maity@toradex.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +/* OCOTP Register Offsets */
> +#define OCOTP_CTRL_REG 0x00
> +#define OCOTP_CTRL_SET 0x04
> +#define OCOTP_CTRL_CLR 0x08
> +#define OCOTP_TIMING 0x10
> +#define OCOTP_DATA 0x20
> +#define OCOTP_READ_CTRL_REG 0x30
> +#define OCOTP_READ_FUSE_DATA 0x40
> +
> +/* OCOTP Register bits and masks */
> +#define OCOTP_CTRL_WR_UNLOCK 16
> +#define OCOTP_CTRL_WR_UNLOCK_KEY 0x3E77
> +#define OCOTP_CTRL_WR_UNLOCK_MASK 0xFFFF0000
> +#define OCOTP_CTRL_ADDR 0
> +#define OCOTP_CTRL_ADDR_MASK 0x7F
> +#define OCOTP_CTRL_RELOAD_SHADOWS (0x1 << 10)
> +#define OCOTP_CTRL_ERROR (0x1 << 9)
> +#define OCOTP_CTRL_BUSY (0x1 << 8)

You can use the BIT() macro here.

> +
> +#define OCOTP_TIMING_STROBE_READ 16
> +#define OCOTP_TIMING_STROBE_READ_MASK 0x003F0000
> +#define OCOTP_TIMING_RELAX 12
> +#define OCOTP_TIMING_RELAX_MASK 0x0000F000
> +#define OCOTP_TIMING_STROBE_PROG 0
> +#define OCOTP_TIMING_STROBE_PROG_MASK 0x00000FFF
> +
> +#define OCOTP_READ_CTRL_READ_FUSE 0x1
> +
> +#define VF610_OCOTP_TIMEOUT 100000
> +
> +#define BF(value, field) (((value) << field) & field##_MASK)
> +
> +#define DEF_RELAX 20
> +
> +struct vf610_ocotp_dev {
> + void __iomem *base;
> + struct clk *clk;
> + struct device *dev;
> + struct resource *res;
> + struct regmap *regmap;
> + struct nvmem_device *nvmem;
> +};

Some member of this struct seems unnecessary to me. Please
remove the unused one.

> +
> +static int ocotp_timing;

How about storing the timings in struct above?

> +
> +static u8 valid_fuse_addr[] = {
> + 0x00, 0x01, 0x02, 0x04, 0x0F, 0x20, 0x21, 0x22, 0x23, 0x24,
> + 0x25, 0x26, 0x27, 0x28, 0x2F, 0x38, 0x39, 0x3A, 0x3B, 0x3C,
> + 0x3D, 0x3E, 0x3F
> +};

const?

> +
> +static int vf610_ocotp_wait_busy(void __iomem *base)
> +{
> + int timeout = VF610_OCOTP_TIMEOUT;
> +
> + while ((readl(base) & OCOTP_CTRL_BUSY) && --timeout)
> + udelay(10);
> +
> + if (!timeout) {
> + writel(OCOTP_CTRL_ERROR, base + OCOTP_CTRL_CLR);
> + return -ETIMEDOUT;
> + }
> +
> + udelay(10);
> +
> + return 0;
> +}
> +
> +static int vf610_ocotp_calculate_timing(struct vf610_ocotp_dev *ocotp_dev)
> +{
> + u32 clk_rate;
> + u32 relax, strobe_read, strobe_prog;
> + u32 timing;
> +
> + clk_rate = clk_get_rate(ocotp_dev->clk);

If clk_get_rate() fails, then we should abort with a warning.

> +
> + relax = clk_rate / (1000000000 / DEF_RELAX) - 1;
> + strobe_prog = clk_rate / (1000000000 / 10000) + 2 * (DEF_RELAX + 1) - 1;
> + strobe_read = clk_rate / (1000000000 / 40) + 2 * (DEF_RELAX + 1) - 1;

A little explanation of the calculation would be helpful.

> +
> + timing = BF(relax, OCOTP_TIMING_RELAX);
> + timing |= BF(strobe_read, OCOTP_TIMING_STROBE_READ);
> + timing |= BF(strobe_prog, OCOTP_TIMING_STROBE_PROG);
> +
> + return timing;
> +}
> +
> +static int vf610_ocotp_set_timing(void __iomem *base, int timing)
> +{
> + writel(timing, base + OCOTP_TIMING);
> +
> + return 0;
> +}
> +
> +static int vf610_ocotp_write(void *context, const void *data, size_t count)
> +{
> + return 0;
> +}
> +
> +static int vf610_ocotp_read(void *context,
> + const void *offset, size_t reg_size,
> + void *val, size_t val_size)
> +{
> + void __iomem *ocotp_base = context;
> + u32 *buf = val;
> + u32 reg;
> + int ret;
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(valid_fuse_addr); i++) {
> + vf610_ocotp_set_timing(ocotp_base, ocotp_timing);
> + ret = vf610_ocotp_wait_busy(ocotp_base + OCOTP_CTRL_REG);
> + if (ret)
> + return ret;

Is it really necessary to set the timing in the loop, instead before?

> +
> + reg = readl(ocotp_base + OCOTP_CTRL_REG);
> + reg &= ~OCOTP_CTRL_ADDR_MASK;
> + reg &= ~OCOTP_CTRL_WR_UNLOCK_MASK;
> + reg |= BF(valid_fuse_addr[i], OCOTP_CTRL_ADDR);
> + writel(reg, ocotp_base + OCOTP_CTRL_REG);
> +
> + writel(OCOTP_READ_CTRL_READ_FUSE,
> + ocotp_base + OCOTP_READ_CTRL_REG);
> + ret = vf610_ocotp_wait_busy(ocotp_base + OCOTP_CTRL_REG);
> + if (ret)
> + return ret;
> +
> + if (readl(ocotp_base) & OCOTP_CTRL_ERROR) {
> + pr_err("Error reading from fuse address %d\n",
> + valid_fuse_addr[i]);

You could use dev_err() when storing vf610_ocotp_dev in the context.

> + writel(OCOTP_CTRL_ERROR, ocotp_base + OCOTP_CTRL_CLR);

Shouldn't the function abort here?

> + }
> +
> + *buf++ = readl(ocotp_base + OCOTP_READ_FUSE_DATA);
> + }
> +
> + return 0;
> +}
> +
> +static struct regmap_bus vf610_ocotp_bus = {
> + .read = vf610_ocotp_read,
> + .write = vf610_ocotp_write,
> + .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
> + .val_format_endian_default = REGMAP_ENDIAN_NATIVE,
> +};
> +
> +static struct regmap_config ocotp_regmap_config = {
> + .reg_bits = 32,
> + .val_bits = 32,
> + .reg_stride = 4,
> +};
> +
> +static struct nvmem_config ocotp_config = {
> + .name = "ocotp",
> + .owner = THIS_MODULE,
> +};
> +
> +static const struct of_device_id ocotp_of_match[] = {
> + { .compatible = "fsl,vf610-ocotp",},
> + {/* sentinel */},
> +};
> +MODULE_DEVICE_TABLE(of, ocotp_of_match);
> +
> +static int vf610_ocotp_remove(struct platform_device *pdev)
> +{
> + struct vf610_ocotp_dev *ocotp_dev = platform_get_drvdata(pdev);
> +
> + return nvmem_unregister(ocotp_dev->nvmem);
> +}
> +
> +static int vf610_ocotp_probe(struct platform_device *pdev)
> +{
> + struct vf610_ocotp_dev *ocotp_dev;
> +
> + ocotp_dev = devm_kzalloc(&pdev->dev,
> + sizeof(struct vf610_ocotp_dev), GFP_KERNEL);
> + if (!ocotp_dev)
> + return -ENOMEM;
> +
> + ocotp_dev->dev = &pdev->dev;
> +
> + ocotp_dev->res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + ocotp_dev->base = devm_ioremap_resource(ocotp_dev->dev, ocotp_dev->res);
> + if (IS_ERR(ocotp_dev->base))
> + return PTR_ERR(ocotp_dev->base);
> +
> + ocotp_dev->clk = devm_clk_get(ocotp_dev->dev, "ocotp");
> + if (IS_ERR(ocotp_dev->clk)) {
> + dev_err(ocotp_dev->dev, "failed getting clock, err = %ld\n",
> + PTR_ERR(ocotp_dev->clk));
> + return PTR_ERR(ocotp_dev->clk);
> + }
> +
> + ocotp_regmap_config.max_register = resource_size(ocotp_dev->res) - 1;

Looking at valid_fuse_addr shows me 0x3F as last valid register. So the rest
of the buffer ( 0xD00 - sizeof(valid_fuse_addr) ) in case of raw access could be
uninitializied.

Regards
Stefan
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