1 files changed, 31 insertions, 6 deletions

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index a31a1db07aa4..064b99204d9a 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -265,6 +265,9 @@ static bool spi_mem_internal_supports_op(struct spi_mem *mem,
  */
 bool spi_mem_supports_op(struct spi_mem *mem, const struct spi_mem_op *op)
 {
+	/* Make sure the operation frequency is correct before going futher */
+	spi_mem_adjust_op_freq(mem, (struct spi_mem_op *)op);
+
 	if (spi_mem_check_op(op))
 		return false;
 
@@ -577,6 +580,7 @@ EXPORT_SYMBOL_GPL(spi_mem_adjust_op_freq);
  * spi_mem_calc_op_duration() - Derives the theoretical length (in ns) of an
  *			        operation. This helps finding the best variant
  *			        among a list of possible choices.
+ * @mem: the SPI memory
  * @op: the operation to benchmark
  *
  * Some chips have per-op frequency limitations, PCBs usually have their own
@@ -586,20 +590,41 @@ EXPORT_SYMBOL_GPL(spi_mem_adjust_op_freq);
  * accurate, all these combinations should be rated (eg. with a time estimate)
  * and the best pick should be taken based on these calculations.
  *
- * Returns a ns estimate for the time this op would take.
+ * Returns a ns estimate for the time this op would take, except if no
+ * frequency limit has been set, in this case we return the number of
+ * cycles nevertheless to allow callers to distinguish which operation
+ * would be the fastest at iso-frequency.
  */
-u64 spi_mem_calc_op_duration(struct spi_mem_op *op)
+u64 spi_mem_calc_op_duration(struct spi_mem *mem, struct spi_mem_op *op)
 {
 	u64 ncycles = 0;
-	u32 ns_per_cycles;
+	u64 ps_per_cycles, duration;
+
+	spi_mem_adjust_op_freq(mem, op);
+
+	if (op->max_freq) {
+		ps_per_cycles = 1000000000000ULL;
+		do_div(ps_per_cycles, op->max_freq);
+	} else {
+		/* In this case, the unit is no longer a time unit */
+		ps_per_cycles = 1;
+	}
 
-	ns_per_cycles = 1000000000 / op->max_freq;
 	ncycles += ((op->cmd.nbytes * 8) / op->cmd.buswidth) / (op->cmd.dtr ? 2 : 1);
 	ncycles += ((op->addr.nbytes * 8) / op->addr.buswidth) / (op->addr.dtr ? 2 : 1);
-	ncycles += ((op->dummy.nbytes * 8) / op->dummy.buswidth) / (op->dummy.dtr ? 2 : 1);
+
+	/* Dummy bytes are optional for some SPI flash memory operations */
+	if (op->dummy.nbytes)
+		ncycles += ((op->dummy.nbytes * 8) / op->dummy.buswidth) / (op->dummy.dtr ? 2 : 1);
+
 	ncycles += ((op->data.nbytes * 8) / op->data.buswidth) / (op->data.dtr ? 2 : 1);
 
-	return ncycles * ns_per_cycles;
+	/* Derive the duration in ps */
+	duration = ncycles * ps_per_cycles;
+	/* Convert into ns */
+	do_div(duration, 1000);
+
+	return duration;
 }
 EXPORT_SYMBOL_GPL(spi_mem_calc_op_duration);