Re: [RFC v3 1/9] nvmem: add driver for JZ4780 efuse

From: Paul Cercueil
Date: Mon Feb 17 2020 - 09:59:02 EST

Hi Srinivas,


Le lun., févr. 17, 2020 at 11:36, Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx> a écrit :


On 16/02/2020 19:20, H. Nikolaus Schaller wrote:
From: PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>

This patch brings support for the JZ4780 efuse. Currently it only exposes
a read only access to the entire 8K bits efuse memory and nvmem cells.

Tested-by: Mathieu Malaterre <malat@xxxxxxxxxx>
Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>
Signed-off-by: Mathieu Malaterre <malat@xxxxxxxxxx>
Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
(Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>)
---
drivers/nvmem/Kconfig | 10 ++
drivers/nvmem/Makefile | 2 +
drivers/nvmem/jz4780-efuse.c | 249 +++++++++++++++++++++++++++++++++++
3 files changed, 261 insertions(+)
create mode 100644 drivers/nvmem/jz4780-efuse.c


This patch along with 2/9 should be merged into single patch.
Also please make sure you run checkpatch.pl before sending!

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 35efab1ba8d9..10f8e08f5e31 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -55,6 +55,16 @@ config NVMEM_IMX_OCOTP_SCU
This is a driver for the SCU On-Chip OTP Controller (OCOTP)
available on i.MX8 SoCs.
+config JZ4780_EFUSE
+ tristate "JZ4780 EFUSE Memory Support"
+ depends on MACH_JZ4780 || COMPILE_TEST

what is that this driver depends on MACH_JZ4780 board?


+ depends on HAS_IOMEM
+ help
+ Say Y here to include support for JZ4780 efuse memory found on
+ all JZ4780 SoC based devices.
+ To compile this driver as a module, choose M here: the module
+ will be called nvmem_jz4780_efuse.
+
config NVMEM_LPC18XX_EEPROM
tristate "NXP LPC18XX EEPROM Memory Support"
depends on ARCH_LPC18XX || COMPILE_TEST
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 6b466cd1427b..65a268d17807 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -18,6 +18,8 @@ obj-$(CONFIG_NVMEM_IMX_OCOTP) += nvmem-imx-ocotp.o
nvmem-imx-ocotp-y := imx-ocotp.o
obj-$(CONFIG_NVMEM_IMX_OCOTP_SCU) += nvmem-imx-ocotp-scu.o
nvmem-imx-ocotp-scu-y := imx-ocotp-scu.o
+obj-$(CONFIG_JZ4780_EFUSE) += nvmem_jz4780_efuse.o
+nvmem_jz4780_efuse-y := jz4780-efuse.o
obj-$(CONFIG_NVMEM_LPC18XX_EEPROM) += nvmem_lpc18xx_eeprom.o
nvmem_lpc18xx_eeprom-y := lpc18xx_eeprom.o
obj-$(CONFIG_NVMEM_LPC18XX_OTP) += nvmem_lpc18xx_otp.o
diff --git a/drivers/nvmem/jz4780-efuse.c b/drivers/nvmem/jz4780-efuse.c
new file mode 100644
index 000000000000..ac03e1900ef9
--- /dev/null
+++ b/drivers/nvmem/jz4780-efuse.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * JZ4780 EFUSE Memory Support driver
+ *
+ * Copyright (c) 2017 PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>
+ * Copyright (c) 2020 H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
+ */
+
+/*
+ * Currently supports JZ4780 efuse which has 8K programmable bit.
+ * Efuse is separated into seven segments as below:
+ *
+ * -----------------------------------------------------------------------
+ * | 64 bit | 128 bit | 128 bit | 3520 bit | 8 bit | 2296 bit | 2048 bit |
+ * -----------------------------------------------------------------------
+ *
+ * The rom itself is accessed using a 9 bit address line and an 8 word wide bus
+ * which reads/writes based on strobes. The strobe is configured in the config
+ * register and is based on number of cycles of the bus clock.
+ *
+ * Driver supports read only as the writes are done in the Factory.
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>


+#include <linux/regmap.h>
+#include <linux/timer.h>
?? why do we need these two headers in this patch


+
+#define JZ_EFUCTRL (0x0) /* Control Register */
+#define JZ_EFUCFG (0x4) /* Configure Register*/
+#define JZ_EFUSTATE (0x8) /* Status Register */
+#define JZ_EFUDATA(n) (0xC + (n)*4)
+
+#define JZ_EFUSE_START_ADDR 0x200
+
+#define JZ_EFUSE_EFUCTRL_CS BIT(30)
+#define JZ_EFUSE_EFUCTRL_ADDR_MASK 0x1FF
+#define JZ_EFUSE_EFUCTRL_ADDR_SHIFT 21
+#define JZ_EFUSE_EFUCTRL_LEN_MASK 0x1F
+#define JZ_EFUSE_EFUCTRL_LEN_SHIFT 16
+#define JZ_EFUSE_EFUCTRL_PG_EN BIT(15)
+#define JZ_EFUSE_EFUCTRL_WR_EN BIT(1)
+#define JZ_EFUSE_EFUCTRL_RD_EN BIT(0)
+
+#define JZ_EFUSE_EFUCFG_INT_EN BIT(31)
+#define JZ_EFUSE_EFUCFG_RD_ADJ_MASK 0xF

consider using GENMASK for these masks here.

+#define JZ_EFUSE_EFUCFG_RD_ADJ_SHIFT 20
+#define JZ_EFUSE_EFUCFG_RD_STR_MASK 0xF
+#define JZ_EFUSE_EFUCFG_RD_STR_SHIFT 16
+#define JZ_EFUSE_EFUCFG_WR_ADJ_MASK 0xF
+#define JZ_EFUSE_EFUCFG_WR_ADJ_SHIFT 12
+#define JZ_EFUSE_EFUCFG_WR_STR_MASK 0xFFF
+#define JZ_EFUSE_EFUCFG_WR_STR_SHIFT 0
+
+#define JZ_EFUSE_EFUSTATE_WR_DONE BIT(1)
+#define JZ_EFUSE_EFUSTATE_RD_DONE BIT(0)
+
+struct jz4780_efuse {
+ struct device *dev;
+ void __iomem *iomem;
+ struct clk *clk;
+ unsigned int rd_adj;
+ unsigned int rd_strobe;
+};
+
+/* We read 32 byte chunks to avoid complexity in the driver. */
+static int jz4780_efuse_read_32bytes(struct jz4780_efuse *efuse, char *buf,
+ unsigned int addr)
+{
+ unsigned int tmp = 0;
+ int i = 0;

unnecessary initialization of both variables.

+ int timeout = 1000;
+ int size = 32;

better to #define this STRIDE/CHUNK size. this driver seems to use this value in multiple places.

+
+ /* 1. Set config register */
+ tmp = readl(efuse->iomem + JZ_EFUCFG);
+ tmp &= ~((JZ_EFUSE_EFUCFG_RD_ADJ_MASK << JZ_EFUSE_EFUCFG_RD_ADJ_SHIFT)
+ | (JZ_EFUSE_EFUCFG_RD_STR_MASK << JZ_EFUSE_EFUCFG_RD_STR_SHIFT));
+ tmp |= (efuse->rd_adj << JZ_EFUSE_EFUCFG_RD_ADJ_SHIFT)
+ | (efuse->rd_strobe << JZ_EFUSE_EFUCFG_RD_STR_SHIFT);

very odd indenting.

+ writel(tmp, efuse->iomem + JZ_EFUCFG);
+
+ /*
+ * 2. Set control register to indicate what to read data address,
+ * read data numbers and read enable.
+ */
+ tmp = readl(efuse->iomem + JZ_EFUCTRL);
+ tmp &= ~(JZ_EFUSE_EFUCFG_RD_STR_SHIFT
+ | (JZ_EFUSE_EFUCTRL_ADDR_MASK << JZ_EFUSE_EFUCTRL_ADDR_SHIFT)
+ | JZ_EFUSE_EFUCTRL_PG_EN | JZ_EFUSE_EFUCTRL_WR_EN
+ | JZ_EFUSE_EFUCTRL_WR_EN);
+
+ /* Need to select CS bit if address accesses upper 4Kbits memory */
+ if (addr >= (JZ_EFUSE_START_ADDR + 512))
+ tmp |= JZ_EFUSE_EFUCTRL_CS;
+
+ tmp |= (addr << JZ_EFUSE_EFUCTRL_ADDR_SHIFT)
+ | ((size - 1) << JZ_EFUSE_EFUCTRL_LEN_SHIFT)
+ | JZ_EFUSE_EFUCTRL_RD_EN;
+ writel(tmp, efuse->iomem + JZ_EFUCTRL);
+
+ /*
+ * 3. Wait status register RD_DONE set to 1 or EFUSE interrupted,
+ * software can read EFUSE data buffer 0 - 8 registers.
+ */
+ do {
+ tmp = readl(efuse->iomem + JZ_EFUSTATE);
+ usleep_range(1000, 2000);
+ if (timeout--)
+ break;
+ } while (!(tmp & JZ_EFUSE_EFUSTATE_RD_DONE));
+
+ if (timeout <= 0) {
+ dev_err(efuse->dev, "Timed out while reading\n");
+ return -EAGAIN;
+ }
+
+ for (i = 0; i < (size / 4); i++)
+ *((unsigned int *)(buf + i * 4))

make "unsigned int *buf32" a local variable and use it here, makes it much readable code.

+ = readl(efuse->iomem + JZ_EFUDATA(i));
+
+ return 0;
+}
+
+/* main entry point */
+static int jz4780_efuse_read(void *context, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct jz4780_efuse *efuse = context;
+ int ret;
+
+ while (bytes > 0) {
+ unsigned int start = offset & ~(32 - 1);
+ unsigned chunk = min(bytes, (start + 32 - offset));
+
+ if (start == offset && chunk == 32) {
+ ret = jz4780_efuse_read_32bytes(efuse, val, start);
+ if (ret < 0)
+ return ret;
+
+ } else {
+ char buf[32];
+ ret = jz4780_efuse_read_32bytes(efuse, buf, start);
+ if (ret < 0)
+ return ret;
+
+ memcpy(val, &buf[offset - start], chunk);
+ }
+
+ val += chunk;
+ offset += chunk;
+ bytes -= chunk;
+ }
+
+ return 0;
+}
+
+static struct nvmem_config jz4780_efuse_nvmem_config = {
+ .name = "jz4780-efuse",
+ .read_only = true,

this value comes from device tree bindings, do we still need to specify this here?

I think its semantic is different - devicetree specifies that you want the nvmem to be readonly, this one specifies that the driver cannot do read-write anyway.

With that said, there is no .reg_write, so .read_only will be enforced to 'true' anyway, so it can be removed.

-Paul


+ .size = 1024,
+ .word_size = 1,
+ .stride = 1,
+ .owner = THIS_MODULE,
+ .reg_read = jz4780_efuse_read,
+};
+
+static int jz4780_efuse_probe(struct platform_device *pdev)
+{
+ struct nvmem_device *nvmem;
+ struct jz4780_efuse *efuse;
+ struct resource *res;
+ unsigned long clk_rate;
+ struct device *dev = &pdev->dev;
+
+ efuse = devm_kzalloc(&pdev->dev, sizeof(*efuse), GFP_KERNEL);
+ if (!efuse)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ efuse->iomem = devm_ioremap(&pdev->dev, res->start, resource_size(res));
+ if (IS_ERR(efuse->iomem))
+ return PTR_ERR(efuse->iomem);
+
+ efuse->clk = devm_clk_get(&pdev->dev, "bus_clk");
+ if (IS_ERR(efuse->clk))
+ return PTR_ERR(efuse->clk);

Who is enabling this clk?


+
+ clk_rate = clk_get_rate(efuse->clk);
+ /*
+ * rd_adj and rd_strobe are 4 bit values
+ * bus clk period * (rd_adj + 1) > 6.5ns
+ * bus clk period * (rd_adj + 5 + rd_strobe) > 35ns
+ */
+ efuse->rd_adj = (((6500 * (clk_rate / 1000000)) / 1000000) + 1) - 1;
+ efuse->rd_strobe = ((((35000 * (clk_rate / 1000000)) / 1000000) + 1)
+ - 5 - efuse->rd_adj);
+
+ if ((efuse->rd_adj > 0x1F) || (efuse->rd_strobe > 0x1F)) {
+ dev_err(&pdev->dev, "Cannot set clock configuration\n");
+ return -EINVAL;
+ }
+ efuse->dev = dev;
+
+ jz4780_efuse_nvmem_config.dev = &pdev->dev;
+ jz4780_efuse_nvmem_config.priv = efuse;
+
+ nvmem = nvmem_register(&jz4780_efuse_nvmem_config);

devm variant here?


+ if (IS_ERR(nvmem))
+ return PTR_ERR(nvmem);
+
+ platform_set_drvdata(pdev, nvmem);
+
+ return 0;
+}
+
+static int jz4780_efuse_remove(struct platform_device *pdev)
+{
+ struct nvmem_device *nvmem = platform_get_drvdata(pdev);
+
+ nvmem_unregister(nvmem);
+
+ return 0;
+}
+
+static const struct of_device_id jz4780_efuse_match[] = {
+ { .compatible = "ingenic,jz4780-efuse" },
+ { /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, jz4780_efuse_match);
+
+static struct platform_driver jz4780_efuse_driver = {
+ .probe = jz4780_efuse_probe,
+ .remove = jz4780_efuse_remove,
+ .driver = {
+ .name = "jz4780-efuse",
+ .of_match_table = jz4780_efuse_match,
+ },
+};
+module_platform_driver(jz4780_efuse_driver);
+
+MODULE_AUTHOR("PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>");
+MODULE_AUTHOR("H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Ingenic JZ4780 efuse driver");
+MODULE_LICENSE("GPL v2");