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Subject[PATCH 3/8] nvmem: Add RAVE SP EEPROM driver
Date
From: Andrey Smirnov <andrew.smirnov@gmail.com>

Add driver providing access to EEPROMs connected to RAVE SP devices

Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: linux-kernel@vger.kernel.org
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
drivers/nvmem/Kconfig | 6 +
drivers/nvmem/Makefile | 3 +
drivers/nvmem/rave-sp-eeprom.c | 357 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 366 insertions(+)
create mode 100644 drivers/nvmem/rave-sp-eeprom.c

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 1090924efdb1..54a3c298247b 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -175,4 +175,10 @@ config NVMEM_SNVS_LPGPR
This driver can also be built as a module. If so, the module
will be called nvmem-snvs-lpgpr.

+config RAVE_SP_EEPROM
+ tristate "Rave SP EEPROM Support"
+ depends on RAVE_SP_CORE
+ help
+ Say y here to enable Rave SP EEPROM support.
+
endif
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index e54dcfa6565a..27e96a8efd1c 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -37,3 +37,6 @@ obj-$(CONFIG_MESON_MX_EFUSE) += nvmem_meson_mx_efuse.o
nvmem_meson_mx_efuse-y := meson-mx-efuse.o
obj-$(CONFIG_NVMEM_SNVS_LPGPR) += nvmem_snvs_lpgpr.o
nvmem_snvs_lpgpr-y := snvs_lpgpr.o
+obj-$(CONFIG_RAVE_SP_EEPROM) += nvmem-rave-sp-eeprom.o
+nvmem-rave-sp-eeprom-y := rave-sp-eeprom.o
+
diff --git a/drivers/nvmem/rave-sp-eeprom.c b/drivers/nvmem/rave-sp-eeprom.c
new file mode 100644
index 000000000000..50aeea6ec6cc
--- /dev/null
+++ b/drivers/nvmem/rave-sp-eeprom.c
@@ -0,0 +1,357 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * EEPROM driver for RAVE SP
+ *
+ * Copyright (C) 2018 Zodiac Inflight Innovations
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/mfd/rave-sp.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/sizes.h>
+
+/**
+ * enum rave_sp_eeprom_access_type - Supported types of EEPROM access
+ *
+ * @RAVE_SP_EEPROM_WRITE: EEPROM write
+ * @RAVE_SP_EEPROM_READ: EEPROM read
+ */
+enum rave_sp_eeprom_access_type {
+ RAVE_SP_EEPROM_WRITE = 0,
+ RAVE_SP_EEPROM_READ = 1,
+};
+
+/**
+ * enum rave_sp_eeprom_header_size - EEPROM command header sizes
+ *
+ * @RAVE_SP_EEPROM_HEADER_SMALL: EEPROM header size for "small" devices (< 8K)
+ * @RAVE_SP_EEPROM_HEADER_BIG: EEPROM header size for "big" devices (> 8K)
+ */
+enum rave_sp_eeprom_header_size {
+ RAVE_SP_EEPROM_HEADER_SMALL = 4U,
+ RAVE_SP_EEPROM_HEADER_BIG = 5U,
+};
+
+#define RAVE_SP_EEPROM_PAGE_SIZE 32U
+
+/**
+ * struct rave_sp_eeprom_page - RAVE SP EEPROM page
+ *
+ * @type: Access type (see enum rave_sp_eeprom_access_type)
+ * @success: Success flag (Success = 1, Failure = 0)
+ * @data: Read data
+
+ * Note this structure corresponds to RSP_*_EEPROM payload from RAVE
+ * SP ICD
+ */
+struct rave_sp_eeprom_page {
+ u8 type;
+ u8 success;
+ u8 data[RAVE_SP_EEPROM_PAGE_SIZE];
+} __packed;
+
+/**
+ * struct rave_sp_eeprom - RAVE SP EEPROM device
+ *
+ * @sp: Pointer to parent RAVE SP device
+ * @mutex: Lock protecting access to EEPROM
+ * @address: EEPROM device address
+ * @header_size: Size of EEPROM command header for this device
+ * @dev: Pointer to corresponding struct device used for logging
+ */
+struct rave_sp_eeprom {
+ struct rave_sp *sp;
+ struct mutex mutex;
+ u8 address;
+ unsigned int header_size;
+ struct device *dev;
+};
+
+/**
+ * rave_sp_eeprom_io - Low-level part of EEPROM page access
+ *
+ * @eeprom: EEPROM device to write to
+ * @type: EEPROM access type (read or write)
+ * @idx: number of the EEPROM page
+ * @page: Data to write or buffer to store result (via page->data)
+ *
+ * This function does all of the low-level work required to perform a
+ * EEPROM access. This includes formatting correct command payload,
+ * sending it and checking received results.
+ *
+ * Returns zero in case of success or negative error code in
+ * case of failure.
+ */
+static int rave_sp_eeprom_io(struct rave_sp_eeprom *eeprom,
+ enum rave_sp_eeprom_access_type type,
+ u16 idx,
+ struct rave_sp_eeprom_page *page)
+{
+ const bool is_write = type == RAVE_SP_EEPROM_WRITE;
+ const unsigned int data_size = is_write ? sizeof(page->data) : 0;
+ const unsigned int cmd_size = eeprom->header_size + data_size;
+ const unsigned int rsp_size =
+ is_write ? sizeof(*page) - sizeof(page->data) : sizeof(*page);
+ unsigned int offset = 0;
+ u8 cmd[cmd_size];
+ int ret;
+
+ cmd[offset++] = eeprom->address;
+ cmd[offset++] = 0;
+ cmd[offset++] = type;
+ cmd[offset++] = idx;
+
+ /*
+ * If there's still room in this command's header it means we
+ * are talkin to EEPROM that uses 16-bit page numbers and we
+ * have to specify index's MSB in payload as well.
+ */
+ if (offset < eeprom->header_size)
+ cmd[offset++] = idx >> 8;
+ /*
+ * Copy our data to write to command buffer first. In case of
+ * a read data_size should be zero and memcpy would become a
+ * no-op
+ */
+ memcpy(&cmd[offset], page->data, data_size);
+
+ ret = rave_sp_exec(eeprom->sp, cmd, cmd_size, page, rsp_size);
+ if (ret)
+ return ret;
+
+ if (page->type != type)
+ return -EPROTO;
+
+ if (!page->success)
+ return -EIO;
+
+ return 0;
+}
+
+/**
+ * rave_sp_eeprom_page_access - Access single EEPROM page
+ *
+ * @eeprom: EEPROM device to access
+ * @type: Access type to perform (read or write)
+ * @offset: Offset within EEPROM to access
+ * @data: Data buffer
+ * @data_len: Size of the data buffer
+ *
+ * This function performs a generic access to a single page or a
+ * portion thereof. Requested access MUST NOT cross the EEPROM page
+ * boundary.
+ *
+ * Returns zero in case of success or negative error code in
+ * case of failure.
+ */
+static int
+rave_sp_eeprom_page_access(struct rave_sp_eeprom *eeprom,
+ enum rave_sp_eeprom_access_type type,
+ unsigned int offset, u8 *data,
+ size_t data_len)
+{
+ const unsigned int page_offset = offset % RAVE_SP_EEPROM_PAGE_SIZE;
+ const unsigned int page_nr = offset / RAVE_SP_EEPROM_PAGE_SIZE;
+ struct rave_sp_eeprom_page page;
+ int ret;
+
+ /*
+ * This function will not work if data access we've been asked
+ * to do is crossing EEPROM page boundary. Normally this
+ * should never happen and getting here would indicate a bug
+ * in the code.
+ */
+ if (WARN_ON(data_len > sizeof(page.data) - page_offset))
+ return -EINVAL;
+
+ if (type == RAVE_SP_EEPROM_WRITE) {
+ /*
+ * If doing a partial write we need to do a read first
+ * to fill the rest of the page with correct data.
+ */
+ if (data_len < RAVE_SP_EEPROM_PAGE_SIZE) {
+ ret = rave_sp_eeprom_io(eeprom, RAVE_SP_EEPROM_READ,
+ page_nr, &page);
+ if (ret)
+ return ret;
+ }
+
+ memcpy(&page.data[page_offset], data, data_len);
+ }
+
+ ret = rave_sp_eeprom_io(eeprom, type, page_nr, &page);
+ if (ret)
+ return ret;
+
+ /*
+ * Since we receive the result of the read via 'page.data'
+ * buffer we need to copy that to 'data'
+ */
+ if (type == RAVE_SP_EEPROM_READ)
+ memcpy(data, &page.data[page_offset], data_len);
+
+ return 0;
+}
+
+/**
+ * rave_sp_eeprom_access - Access EEPROM data
+ *
+ * @eeprom: EEPROM device to access
+ * @type: Access type to perform (read or write)
+ * @offset: Offset within EEPROM to access
+ * @data: Data buffer
+ * @data_len: Size of the data buffer
+ *
+ * This function performs a generic access (either read or write) at
+ * arbitrary offset (not necessary page aligned) of arbitrary length
+ * (is not constrained by EEPROM page size).
+ *
+ * Returns zero in case of success or negative error code in case of
+ * failure.
+ */
+static int rave_sp_eeprom_access(struct rave_sp_eeprom *eeprom,
+ enum rave_sp_eeprom_access_type type,
+ unsigned int offset, u8 *data,
+ unsigned int data_len)
+{
+ unsigned int residue;
+ unsigned int chunk;
+ unsigned int head;
+ int ret;
+
+ mutex_lock(&eeprom->mutex);
+
+ head = offset % RAVE_SP_EEPROM_PAGE_SIZE;
+ residue = data_len;
+
+ do {
+ /*
+ * First iteration, if we are doing an access that is
+ * not 32-byte aligned, we need to access only data up
+ * to a page boundary to avoid corssing it in
+ * rave_sp_eeprom_page_access()
+ */
+ if (unlikely(head)) {
+ chunk = RAVE_SP_EEPROM_PAGE_SIZE - head;
+ /*
+ * This can only happen once per
+ * rave_sp_eeprom_access() call, so we set
+ * head to zero to process all the other
+ * iterations normally.
+ */
+ head = 0;
+ } else {
+ chunk = RAVE_SP_EEPROM_PAGE_SIZE;
+ }
+
+ /*
+ * We should never read more that 'residue' bytes
+ */
+ chunk = min(chunk, residue);
+ ret = rave_sp_eeprom_page_access(eeprom, type, offset,
+ data, chunk);
+ if (ret)
+ goto out;
+
+ residue -= chunk;
+ offset += chunk;
+ data += chunk;
+ } while (residue);
+out:
+ mutex_unlock(&eeprom->mutex);
+ return ret;
+}
+
+static int rave_sp_eeprom_reg_read(void *eeprom, unsigned int offset,
+ void *val, size_t bytes)
+{
+ return rave_sp_eeprom_access(eeprom, RAVE_SP_EEPROM_READ,
+ offset, val, bytes);
+}
+
+static int rave_sp_eeprom_reg_write(void *eeprom, unsigned int offset,
+ void *val, size_t bytes)
+{
+ return rave_sp_eeprom_access(eeprom, RAVE_SP_EEPROM_WRITE,
+ offset, val, bytes);
+}
+
+static int rave_sp_eeprom_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct rave_sp *sp = dev_get_drvdata(dev->parent);
+ struct device_node *np = dev->of_node;
+ struct nvmem_config config = { 0 };
+ struct rave_sp_eeprom *eeprom;
+ struct nvmem_device *nvmem;
+ u32 reg[2], size;
+
+ if (of_property_read_u32_array(np, "reg", reg, ARRAY_SIZE(reg))) {
+ dev_err(dev, "Failed to parse \"reg\" property\n");
+ return -EINVAL;
+ }
+
+ size = reg[1];
+ /*
+ * Per ICD, we have no more than 2 bytes to specify EEPROM
+ * page.
+ */
+ if (size > U16_MAX * RAVE_SP_EEPROM_PAGE_SIZE) {
+ dev_err(dev, "Specified size is too big\n");
+ return -EINVAL;
+ }
+
+ eeprom = devm_kzalloc(dev, sizeof(*eeprom), GFP_KERNEL);
+ if (!eeprom)
+ return -ENOMEM;
+
+ eeprom->address = reg[0];
+ eeprom->sp = sp;
+ eeprom->dev = dev;
+
+ if (size > SZ_8K)
+ eeprom->header_size = RAVE_SP_EEPROM_HEADER_BIG;
+ else
+ eeprom->header_size = RAVE_SP_EEPROM_HEADER_SMALL;
+
+ mutex_init(&eeprom->mutex);
+
+ config.id = -1;
+ of_property_read_string(np, "zii,eeprom-name", &config.name);
+ config.priv = eeprom;
+ config.dev = dev;
+ config.size = size;
+ config.reg_read = rave_sp_eeprom_reg_read;
+ config.reg_write = rave_sp_eeprom_reg_write;
+ config.word_size = 1;
+ config.stride = 1;
+
+ nvmem = devm_nvmem_register(dev, &config);
+
+ return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id rave_sp_eeprom_of_match[] = {
+ { .compatible = "zii,rave-sp-eeprom" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, rave_sp_eeprom_of_match);
+
+static struct platform_driver rave_sp_eeprom_driver = {
+ .probe = rave_sp_eeprom_probe,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = rave_sp_eeprom_of_match,
+ },
+};
+module_platform_driver(rave_sp_eeprom_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Andrey Vostrikov <andrey.vostrikov@cogentembedded.com>");
+MODULE_AUTHOR("Nikita Yushchenko <nikita.yoush@cogentembedded.com>");
+MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@gmail.com>");
+MODULE_DESCRIPTION("RAVE SP EEPROM driver");
--
2.16.2
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