developer | 44e1bbf | 2022-01-28 17:20:00 +0800 | [diff] [blame] | 1 | From 8dc0b1158dcffd78ea2b3a5604b82ee826de687b Mon Sep 17 00:00:00 2001 |
| 2 | From: Zhanyong Wang <zhanyong.wang@mediatek.com> |
| 3 | Date: Mon, 8 Nov 2021 13:58:51 +0800 |
| 4 | Subject: [PATCH 1/5] nvmem: core: Add functions to make number reading easy |
| 5 | |
| 6 | Sometimes the clients of nvmem just want to get a number out of |
| 7 | nvmem. They don't want to think about exactly how many bytes the nvmem |
| 8 | cell took up. They just want the number. Let's make it easy. |
| 9 | |
| 10 | In general this concept is useful because nvmem space is precious and |
| 11 | usually the fewest bits are allocated that will hold a given value on |
| 12 | a given system. However, even though small numbers might be fine on |
| 13 | one system that doesn't mean that logically the number couldn't be |
| 14 | bigger. Imagine nvmem containing a max frequency for a component. On |
| 15 | one system perhaps that fits in 16 bits. On another system it might |
| 16 | fit in 32 bits. The code reading this number doesn't care--it just |
| 17 | wants the number. |
| 18 | |
| 19 | We'll provide two functions: nvmem_cell_read_variable_le_u32() and |
| 20 | nvmem_cell_read_variable_le_u64(). |
| 21 | |
| 22 | Comparing these to the existing functions like nvmem_cell_read_u32(): |
| 23 | * These new functions have no problems if the value was stored in |
| 24 | nvmem in fewer bytes. It's OK to use these function as long as the |
| 25 | value stored will fit in 32-bits (or 64-bits). |
| 26 | * These functions avoid problems that the earlier APIs had with bit |
| 27 | offsets. For instance, you can't use nvmem_cell_read_u32() to read a |
| 28 | value has nbits=32 and bit_offset=4 because the nvmem cell must be |
| 29 | at least 5 bytes big to hold this value. The new API accounts for |
| 30 | this and works fine. |
| 31 | * These functions make it very explicit that they assume that the |
| 32 | number was stored in little endian format. The old functions made |
| 33 | this assumption whenever bit_offset was non-zero (see |
| 34 | nvmem_shift_read_buffer_in_place()) but didn't whenever the |
| 35 | bit_offset was zero. |
| 36 | |
| 37 | NOTE: it's assumed that we don't need an 8-bit or 16-bit version of |
| 38 | this function. The 32-bit version of the function can be used to read |
| 39 | 8-bit or 16-bit data. |
| 40 | |
| 41 | At the moment, I'm only adding the "unsigned" versions of these |
| 42 | functions, but if it ends up being useful someone could add a "signed" |
| 43 | version that did 2's complement sign extension. |
| 44 | |
| 45 | At the moment, I'm only adding the "little endian" versions of these |
| 46 | functions. Adding the "big endian" version would require adding "big |
| 47 | endian" support to nvmem_shift_read_buffer_in_place(). |
| 48 | |
| 49 | Signed-off-by: Douglas Anderson <dianders@chromium.org> |
| 50 | Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> |
| 51 | Link: https://lore.kernel.org/r/20210330111241.19401-7-srinivas.kandagatla@linaro.org |
| 52 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| 53 | Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com> |
| 54 | Signed-off-by: Zhanyong Wang <zhanyong.wang@mediatek.com> |
| 55 | Change-Id: I3e1d96ec1680812d5e24681c79852c9b36899559 |
| 56 | --- |
| 57 | drivers/nvmem/core.c | 161 +++++++++++++++++++++++++++------ |
| 58 | include/linux/nvmem-consumer.h | 15 +++ |
| 59 | 2 files changed, 150 insertions(+), 26 deletions(-) |
| 60 | |
| 61 | diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c |
| 62 | index c0f4324d8f7c..e26b25b5c288 100644 |
| 63 | --- a/drivers/nvmem/core.c |
| 64 | +++ b/drivers/nvmem/core.c |
| 65 | @@ -1102,16 +1102,8 @@ int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len) |
| 66 | } |
| 67 | EXPORT_SYMBOL_GPL(nvmem_cell_write); |
| 68 | |
| 69 | -/** |
| 70 | - * nvmem_cell_read_u16() - Read a cell value as an u16 |
| 71 | - * |
| 72 | - * @dev: Device that requests the nvmem cell. |
| 73 | - * @cell_id: Name of nvmem cell to read. |
| 74 | - * @val: pointer to output value. |
| 75 | - * |
| 76 | - * Return: 0 on success or negative errno. |
| 77 | - */ |
| 78 | -int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val) |
| 79 | +static int nvmem_cell_read_common(struct device *dev, const char *cell_id, |
| 80 | + void *val, size_t count) |
| 81 | { |
| 82 | struct nvmem_cell *cell; |
| 83 | void *buf; |
| 84 | @@ -1126,21 +1118,50 @@ int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val) |
| 85 | nvmem_cell_put(cell); |
| 86 | return PTR_ERR(buf); |
| 87 | } |
| 88 | - if (len != sizeof(*val)) { |
| 89 | + if (len != count) { |
| 90 | kfree(buf); |
| 91 | nvmem_cell_put(cell); |
| 92 | return -EINVAL; |
| 93 | } |
| 94 | - memcpy(val, buf, sizeof(*val)); |
| 95 | + memcpy(val, buf, count); |
| 96 | kfree(buf); |
| 97 | nvmem_cell_put(cell); |
| 98 | |
| 99 | return 0; |
| 100 | } |
| 101 | + |
| 102 | +/** |
| 103 | + * nvmem_cell_read_u8() - Read a cell value as a u8 |
| 104 | + * |
| 105 | + * @dev: Device that requests the nvmem cell. |
| 106 | + * @cell_id: Name of nvmem cell to read. |
| 107 | + * @val: pointer to output value. |
| 108 | + * |
| 109 | + * Return: 0 on success or negative errno. |
| 110 | + */ |
| 111 | +int nvmem_cell_read_u8(struct device *dev, const char *cell_id, u8 *val) |
| 112 | +{ |
| 113 | + return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val)); |
| 114 | +} |
| 115 | +EXPORT_SYMBOL_GPL(nvmem_cell_read_u8); |
| 116 | + |
| 117 | +/** |
| 118 | + * nvmem_cell_read_u16() - Read a cell value as a u16 |
| 119 | + * |
| 120 | + * @dev: Device that requests the nvmem cell. |
| 121 | + * @cell_id: Name of nvmem cell to read. |
| 122 | + * @val: pointer to output value. |
| 123 | + * |
| 124 | + * Return: 0 on success or negative errno. |
| 125 | + */ |
| 126 | +int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val) |
| 127 | +{ |
| 128 | + return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val)); |
| 129 | +} |
| 130 | EXPORT_SYMBOL_GPL(nvmem_cell_read_u16); |
| 131 | |
| 132 | /** |
| 133 | - * nvmem_cell_read_u32() - Read a cell value as an u32 |
| 134 | + * nvmem_cell_read_u32() - Read a cell value as a u32 |
| 135 | * |
| 136 | * @dev: Device that requests the nvmem cell. |
| 137 | * @cell_id: Name of nvmem cell to read. |
| 138 | @@ -1149,32 +1170,120 @@ EXPORT_SYMBOL_GPL(nvmem_cell_read_u16); |
| 139 | * Return: 0 on success or negative errno. |
| 140 | */ |
| 141 | int nvmem_cell_read_u32(struct device *dev, const char *cell_id, u32 *val) |
| 142 | +{ |
| 143 | + return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val)); |
| 144 | +} |
| 145 | +EXPORT_SYMBOL_GPL(nvmem_cell_read_u32); |
| 146 | + |
| 147 | +/** |
| 148 | + * nvmem_cell_read_u64() - Read a cell value as a u64 |
| 149 | + * |
| 150 | + * @dev: Device that requests the nvmem cell. |
| 151 | + * @cell_id: Name of nvmem cell to read. |
| 152 | + * @val: pointer to output value. |
| 153 | + * |
| 154 | + * Return: 0 on success or negative errno. |
| 155 | + */ |
| 156 | +int nvmem_cell_read_u64(struct device *dev, const char *cell_id, u64 *val) |
| 157 | +{ |
| 158 | + return nvmem_cell_read_common(dev, cell_id, val, sizeof(*val)); |
| 159 | +} |
| 160 | +EXPORT_SYMBOL_GPL(nvmem_cell_read_u64); |
| 161 | + |
| 162 | +static const void *nvmem_cell_read_variable_common(struct device *dev, |
| 163 | + const char *cell_id, |
| 164 | + size_t max_len, size_t *len) |
| 165 | { |
| 166 | struct nvmem_cell *cell; |
| 167 | + int nbits; |
| 168 | void *buf; |
| 169 | - size_t len; |
| 170 | |
| 171 | cell = nvmem_cell_get(dev, cell_id); |
| 172 | if (IS_ERR(cell)) |
| 173 | - return PTR_ERR(cell); |
| 174 | + return cell; |
| 175 | |
| 176 | - buf = nvmem_cell_read(cell, &len); |
| 177 | - if (IS_ERR(buf)) { |
| 178 | - nvmem_cell_put(cell); |
| 179 | - return PTR_ERR(buf); |
| 180 | - } |
| 181 | - if (len != sizeof(*val)) { |
| 182 | + nbits = cell->nbits; |
| 183 | + buf = nvmem_cell_read(cell, len); |
| 184 | + nvmem_cell_put(cell); |
| 185 | + if (IS_ERR(buf)) |
| 186 | + return buf; |
| 187 | + |
| 188 | + /* |
| 189 | + * If nbits is set then nvmem_cell_read() can significantly exaggerate |
| 190 | + * the length of the real data. Throw away the extra junk. |
| 191 | + */ |
| 192 | + if (nbits) |
| 193 | + *len = DIV_ROUND_UP(nbits, 8); |
| 194 | + |
| 195 | + if (*len > max_len) { |
| 196 | kfree(buf); |
| 197 | - nvmem_cell_put(cell); |
| 198 | - return -EINVAL; |
| 199 | + return ERR_PTR(-ERANGE); |
| 200 | } |
| 201 | - memcpy(val, buf, sizeof(*val)); |
| 202 | + |
| 203 | + return buf; |
| 204 | +} |
| 205 | + |
| 206 | +/** |
| 207 | + * nvmem_cell_read_variable_le_u32() - Read up to 32-bits of data as a little endian number. |
| 208 | + * |
| 209 | + * @dev: Device that requests the nvmem cell. |
| 210 | + * @cell_id: Name of nvmem cell to read. |
| 211 | + * @val: pointer to output value. |
| 212 | + * |
| 213 | + * Return: 0 on success or negative errno. |
| 214 | + */ |
| 215 | +int nvmem_cell_read_variable_le_u32(struct device *dev, const char *cell_id, |
| 216 | + u32 *val) |
| 217 | +{ |
| 218 | + size_t len; |
| 219 | + const u8 *buf; |
| 220 | + int i; |
| 221 | + |
| 222 | + buf = nvmem_cell_read_variable_common(dev, cell_id, sizeof(*val), &len); |
| 223 | + if (IS_ERR(buf)) |
| 224 | + return PTR_ERR(buf); |
| 225 | + |
| 226 | + /* Copy w/ implicit endian conversion */ |
| 227 | + *val = 0; |
| 228 | + for (i = 0; i < len; i++) |
| 229 | + *val |= buf[i] << (8 * i); |
| 230 | |
| 231 | kfree(buf); |
| 232 | - nvmem_cell_put(cell); |
| 233 | + |
| 234 | return 0; |
| 235 | } |
| 236 | -EXPORT_SYMBOL_GPL(nvmem_cell_read_u32); |
| 237 | +EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u32); |
| 238 | + |
| 239 | +/** |
| 240 | + * nvmem_cell_read_variable_le_u64() - Read up to 64-bits of data as a little endian number. |
| 241 | + * |
| 242 | + * @dev: Device that requests the nvmem cell. |
| 243 | + * @cell_id: Name of nvmem cell to read. |
| 244 | + * @val: pointer to output value. |
| 245 | + * |
| 246 | + * Return: 0 on success or negative errno. |
| 247 | + */ |
| 248 | +int nvmem_cell_read_variable_le_u64(struct device *dev, const char *cell_id, |
| 249 | + u64 *val) |
| 250 | +{ |
| 251 | + size_t len; |
| 252 | + const u8 *buf; |
| 253 | + int i; |
| 254 | + |
| 255 | + buf = nvmem_cell_read_variable_common(dev, cell_id, sizeof(*val), &len); |
| 256 | + if (IS_ERR(buf)) |
| 257 | + return PTR_ERR(buf); |
| 258 | + |
| 259 | + /* Copy w/ implicit endian conversion */ |
| 260 | + *val = 0; |
| 261 | + for (i = 0; i < len; i++) |
| 262 | + *val |= (uint64_t)buf[i] << (8 * i); |
| 263 | + |
| 264 | + kfree(buf); |
| 265 | + |
| 266 | + return 0; |
| 267 | +} |
| 268 | +EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u64); |
| 269 | |
| 270 | /** |
| 271 | * nvmem_device_cell_read() - Read a given nvmem device and cell |
| 272 | diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h |
| 273 | index 5c17cb733224..e328c0f7eef3 100644 |
| 274 | --- a/include/linux/nvmem-consumer.h |
| 275 | +++ b/include/linux/nvmem-consumer.h |
| 276 | @@ -63,6 +63,10 @@ void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len); |
| 277 | int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len); |
| 278 | int nvmem_cell_read_u16(struct device *dev, const char *cell_id, u16 *val); |
| 279 | int nvmem_cell_read_u32(struct device *dev, const char *cell_id, u32 *val); |
| 280 | +int nvmem_cell_read_variable_le_u32(struct device *dev, const char *cell_id, |
| 281 | + u32 *val); |
| 282 | +int nvmem_cell_read_variable_le_u64(struct device *dev, const char *cell_id, |
| 283 | + u64 *val); |
| 284 | |
| 285 | /* direct nvmem device read/write interface */ |
| 286 | struct nvmem_device *nvmem_device_get(struct device *dev, const char *name); |
| 287 | @@ -134,6 +138,17 @@ static inline int nvmem_cell_read_u32(struct device *dev, |
| 288 | { |
| 289 | return -EOPNOTSUPP; |
| 290 | } |
| 291 | +static inline int nvmem_cell_read_variable_le_u32(struct device *dev, |
| 292 | + const char *cell_id, u32 *val) |
| 293 | +{ |
| 294 | + return -ENOSYS; |
| 295 | +} |
| 296 | + |
| 297 | +static inline int nvmem_cell_read_variable_le_u64(struct device *dev, |
| 298 | + const char *cell_id, u64 *val); |
| 299 | +{ |
| 300 | + return -ENOSYS; |
| 301 | +} |
| 302 | |
| 303 | static inline struct nvmem_device *nvmem_device_get(struct device *dev, |
| 304 | const char *name) |
| 305 | -- |
| 306 | 2.18.0 |
| 307 | |