@@ -356,6 +356,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
{
unsigned int tmpbufsize, xferpos = 0, totalxferlen = 0;
struct spi_controller *ctlr = mem->spi->controller;
+ unsigned int xfer_speed = op->max_freq;
struct spi_transfer xfers[4] = { };
struct spi_message msg;
u8 *tmpbuf;
@@ -368,6 +369,9 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
if (!spi_mem_internal_supports_op(mem, op))
return -EOPNOTSUPP;
+ if (!op->max_freq || op->max_freq > mem->spi->max_speed_hz)
+ ((struct spi_mem_op *)op)->max_freq = mem->spi->max_speed_hz;
+
if (ctlr->mem_ops && ctlr->mem_ops->exec_op && !spi_get_csgpiod(mem->spi, 0)) {
ret = spi_mem_access_start(mem);
if (ret)
@@ -407,6 +411,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
xfers[xferpos].tx_buf = tmpbuf;
xfers[xferpos].len = op->cmd.nbytes;
xfers[xferpos].tx_nbits = op->cmd.buswidth;
+ xfers[xferpos].speed_hz = xfer_speed;
spi_message_add_tail(&xfers[xferpos], &msg);
xferpos++;
totalxferlen++;
@@ -421,6 +426,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
xfers[xferpos].tx_buf = tmpbuf + 1;
xfers[xferpos].len = op->addr.nbytes;
xfers[xferpos].tx_nbits = op->addr.buswidth;
+ xfers[xferpos].speed_hz = xfer_speed;
spi_message_add_tail(&xfers[xferpos], &msg);
xferpos++;
totalxferlen += op->addr.nbytes;
@@ -432,6 +438,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
xfers[xferpos].len = op->dummy.nbytes;
xfers[xferpos].tx_nbits = op->dummy.buswidth;
xfers[xferpos].dummy_data = 1;
+ xfers[xferpos].speed_hz = xfer_speed;
spi_message_add_tail(&xfers[xferpos], &msg);
xferpos++;
totalxferlen += op->dummy.nbytes;
@@ -447,6 +454,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
}
xfers[xferpos].len = op->data.nbytes;
+ xfers[xferpos].speed_hz = xfer_speed;
spi_message_add_tail(&xfers[xferpos], &msg);
xferpos++;
totalxferlen += op->data.nbytes;
@@ -68,6 +68,9 @@ enum spi_mem_data_dir {
SPI_MEM_DATA_OUT,
};
+#define SPI_MEM_OP_MAX_FREQ(__freq) \
+ .max_freq = __freq
+
/**
* struct spi_mem_op - describes a SPI memory operation
* @cmd.nbytes: number of opcode bytes (only 1 or 2 are valid). The opcode is
@@ -95,6 +98,9 @@ enum spi_mem_data_dir {
* operation does not involve transferring data
* @data.buf.in: input buffer (must be DMA-able)
* @data.buf.out: output buffer (must be DMA-able)
+ * @max_freq: frequency limitation wrt this operation. 0 means there is no
+ * specific constraint and the highest achievable frequency can be
+ * attempted).
*/
struct spi_mem_op {
struct {
@@ -132,14 +138,17 @@ struct spi_mem_op {
const void *out;
} buf;
} data;
+
+ unsigned int max_freq;
};
-#define SPI_MEM_OP(__cmd, __addr, __dummy, __data) \
+#define SPI_MEM_OP(__cmd, __addr, __dummy, __data, ...) \
{ \
.cmd = __cmd, \
.addr = __addr, \
.dummy = __dummy, \
.data = __data, \
+ __VA_ARGS__ \
}
/**
In the spi subsystem, the bus frequency is derived as follows: - the controller may expose a minimum and maximum operating frequency - the hardware description, through the spi peripheral properties, advise what is the maximum acceptable frequency from a device/wiring point of view. Transfers must be observed at a frequency which fits both (so in practice, the lowest maximum). Actually, this second point mixes two information and already takes the lowest frequency among: - what the spi device is capable of (what is written in the component datasheet) - what the wiring allows (electromagnetic sensibility, crossovers, terminations, antenna effect, etc). This logic works until spi devices are no longer capable of sustaining their highest frequency regardless of the operation. Spi memories are typically subject to such variation. Some devices are capable of spitting their internally stored data (essentially in read mode) at a very fast rate, typically up to 166MHz on Winbond SPI-NAND chips, using "fast" commands. However, some of the low-end operations, such as regular page read-from-cache commands, are more limited and can only be executed at 54MHz at most. This is currently a problem in the SPI-NAND subsystem. Another situation, even if not yet supported, will be with DTR commands, when the data is latched on both edges of the clock. The same chips as mentioned previously are in this case limited to 80MHz. Yet another example might be continuous reads, which, under certain circumstances, can also run at most at 104 or 120MHz. As a matter of fact, the "one frequency per chip" policy is outdated and more fine grain configuration is needed: we need to allow per-operation frequency limitations. So far, all datasheets I encountered advertise a maximum default frequency, which need to be lowered for certain specific operations. So based on the current infrastructure, we can still expect firmware (device trees in general) to continued advertising the same maximum speed which is a mix between the PCB limitations and the chip maximum capability, and expect per-operation lower frequencies when this is relevant. Add a `struct spi_mem_op` member to carry this information. Not providing this field explicitly from upper layers means that there is no further constraint and the default spi device maximum speed will be carried instead. The SPI_MEM_OP() macro is also expanded with an optional frequency argument, because virtually all operations can be subject to such a limitation, and this will allow for a smooth and discrete transition. For controller drivers which do not implement the spi-mem interface, the per-transfer speed is also set acordingly to a lower (than the maximum default) speed, or 0, to comply with the current API. Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> --- drivers/spi/spi-mem.c | 8 ++++++++ include/linux/spi/spi-mem.h | 11 ++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-)