From fd3bb8f54a88107570334c156efb0c724a261003 Mon Sep 17 00:00:00 2001 From: Evan Green Date: Fri, 27 Nov 2020 10:28:34 +0000 Subject: nvmem: core: Add support for keepout regions Introduce support into the nvmem core for arrays of register ranges that should not result in actual device access. For these regions a constant byte (repeated) is returned instead on read, and writes are quietly ignored and returned as successful. This is useful for instance if certain efuse regions are protected from access by Linux because they contain secret info to another part of the system (like an integrated modem). Signed-off-by: Evan Green Signed-off-by: Srinivas Kandagatla Link: https://lore.kernel.org/r/20201127102837.19366-3-srinivas.kandagatla@linaro.org Signed-off-by: Greg Kroah-Hartman --- drivers/nvmem/core.c | 153 +++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 149 insertions(+), 4 deletions(-) (limited to 'drivers/nvmem/core.c') diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index a09ff8409f60..177f5bf27c6d 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -34,6 +34,8 @@ struct nvmem_device { struct bin_attribute eeprom; struct device *base_dev; struct list_head cells; + const struct nvmem_keepout *keepout; + unsigned int nkeepout; nvmem_reg_read_t reg_read; nvmem_reg_write_t reg_write; struct gpio_desc *wp_gpio; @@ -66,8 +68,8 @@ static LIST_HEAD(nvmem_lookup_list); static BLOCKING_NOTIFIER_HEAD(nvmem_notifier); -static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset, - void *val, size_t bytes) +static int __nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset, + void *val, size_t bytes) { if (nvmem->reg_read) return nvmem->reg_read(nvmem->priv, offset, val, bytes); @@ -75,8 +77,8 @@ static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset, return -EINVAL; } -static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset, - void *val, size_t bytes) +static int __nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset, + void *val, size_t bytes) { int ret; @@ -90,6 +92,88 @@ static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset, return -EINVAL; } +static int nvmem_access_with_keepouts(struct nvmem_device *nvmem, + unsigned int offset, void *val, + size_t bytes, int write) +{ + + unsigned int end = offset + bytes; + unsigned int kend, ksize; + const struct nvmem_keepout *keepout = nvmem->keepout; + const struct nvmem_keepout *keepoutend = keepout + nvmem->nkeepout; + int rc; + + /* + * Skip all keepouts before the range being accessed. + * Keepouts are sorted. + */ + while ((keepout < keepoutend) && (keepout->end <= offset)) + keepout++; + + while ((offset < end) && (keepout < keepoutend)) { + /* Access the valid portion before the keepout. */ + if (offset < keepout->start) { + kend = min(end, keepout->start); + ksize = kend - offset; + if (write) + rc = __nvmem_reg_write(nvmem, offset, val, ksize); + else + rc = __nvmem_reg_read(nvmem, offset, val, ksize); + + if (rc) + return rc; + + offset += ksize; + val += ksize; + } + + /* + * Now we're aligned to the start of this keepout zone. Go + * through it. + */ + kend = min(end, keepout->end); + ksize = kend - offset; + if (!write) + memset(val, keepout->value, ksize); + + val += ksize; + offset += ksize; + keepout++; + } + + /* + * If we ran out of keepouts but there's still stuff to do, send it + * down directly + */ + if (offset < end) { + ksize = end - offset; + if (write) + return __nvmem_reg_write(nvmem, offset, val, ksize); + else + return __nvmem_reg_read(nvmem, offset, val, ksize); + } + + return 0; +} + +static int nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset, + void *val, size_t bytes) +{ + if (!nvmem->nkeepout) + return __nvmem_reg_read(nvmem, offset, val, bytes); + + return nvmem_access_with_keepouts(nvmem, offset, val, bytes, false); +} + +static int nvmem_reg_write(struct nvmem_device *nvmem, unsigned int offset, + void *val, size_t bytes) +{ + if (!nvmem->nkeepout) + return __nvmem_reg_write(nvmem, offset, val, bytes); + + return nvmem_access_with_keepouts(nvmem, offset, val, bytes, true); +} + #ifdef CONFIG_NVMEM_SYSFS static const char * const nvmem_type_str[] = { [NVMEM_TYPE_UNKNOWN] = "Unknown", @@ -533,6 +617,59 @@ nvmem_find_cell_by_name(struct nvmem_device *nvmem, const char *cell_id) return cell; } +static int nvmem_validate_keepouts(struct nvmem_device *nvmem) +{ + unsigned int cur = 0; + const struct nvmem_keepout *keepout = nvmem->keepout; + const struct nvmem_keepout *keepoutend = keepout + nvmem->nkeepout; + + while (keepout < keepoutend) { + /* Ensure keepouts are sorted and don't overlap. */ + if (keepout->start < cur) { + dev_err(&nvmem->dev, + "Keepout regions aren't sorted or overlap.\n"); + + return -ERANGE; + } + + if (keepout->end < keepout->start) { + dev_err(&nvmem->dev, + "Invalid keepout region.\n"); + + return -EINVAL; + } + + /* + * Validate keepouts (and holes between) don't violate + * word_size constraints. + */ + if ((keepout->end - keepout->start < nvmem->word_size) || + ((keepout->start != cur) && + (keepout->start - cur < nvmem->word_size))) { + + dev_err(&nvmem->dev, + "Keepout regions violate word_size constraints.\n"); + + return -ERANGE; + } + + /* Validate keepouts don't violate stride (alignment). */ + if (!IS_ALIGNED(keepout->start, nvmem->stride) || + !IS_ALIGNED(keepout->end, nvmem->stride)) { + + dev_err(&nvmem->dev, + "Keepout regions violate stride.\n"); + + return -EINVAL; + } + + cur = keepout->end; + keepout++; + } + + return 0; +} + static int nvmem_add_cells_from_of(struct nvmem_device *nvmem) { struct device_node *parent, *child; @@ -647,6 +784,8 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) nvmem->type = config->type; nvmem->reg_read = config->reg_read; nvmem->reg_write = config->reg_write; + nvmem->keepout = config->keepout; + nvmem->nkeepout = config->nkeepout; if (!config->no_of_node) nvmem->dev.of_node = config->dev->of_node; @@ -671,6 +810,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) nvmem->dev.groups = nvmem_dev_groups; #endif + if (nvmem->nkeepout) { + rval = nvmem_validate_keepouts(nvmem); + if (rval) + goto err_put_device; + } + dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name); rval = device_register(&nvmem->dev); -- cgit v1.2.3