[PATCH v2 02/27] spi: spi-mem: Add a new controller capability

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

There are spi devices with multiple frequency limitations depending on
the invoked command. We probably do not want to afford running at the
lowest supported frequency all the time, so if we want to get the most
of our hardware, we need to allow per-operation frequency limitations.

Among all the SPI memory controllers, I believe all are capable of
changing the spi frequency on the fly. Some of the drivers do not make
any frequency setup though. And some others will derive a per chip
prescaler value which will be used forever.

Actually changing the frequency on the fly is something new in Linux, so
we need to carefully flag the drivers which do and do not support it. A
controller capability is created for that, and the presence for this
capability will always be checked before accepting such pattern.

Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
---
 drivers/spi/spi-mem.c       | 6 ++++++
 include/linux/spi/spi-mem.h | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 12299ce89a1cc80495858dbbbaa822f2968bb7ab..96374afd0193ca2cf4f50004f66c36dce32894e8 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -191,6 +191,12 @@ bool spi_mem_default_supports_op(struct spi_mem *mem,
 	    op->max_freq < mem->spi->controller->min_speed_hz)
 		return false;
 
+	if (op->max_freq &&
+	    op->max_freq < mem->spi->max_speed_hz) {
+		if (!spi_mem_controller_is_capable(ctlr, per_op_freq))
+			return false;
+	}
+
 	return spi_mem_check_buswidth(mem, op);
 }
 EXPORT_SYMBOL_GPL(spi_mem_default_supports_op);
diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
index 84ec524987921a95963235de4b6f728ef2fc5987..c7a7719c264846ad9fce613ba96d9284ad7893e7 100644
--- a/include/linux/spi/spi-mem.h
+++ b/include/linux/spi/spi-mem.h
@@ -311,11 +311,13 @@ struct spi_controller_mem_ops {
  * @ecc: Supports operations with error correction
  * @swap16: Supports swapping bytes on a 16 bit boundary when configured in
  *	    Octal DTR
+ * @per_op_freq: Supports per operation frequency switching
  */
 struct spi_controller_mem_caps {
 	bool dtr;
 	bool ecc;
 	bool swap16;
+	bool per_op_freq;
 };
 
 #define spi_mem_controller_is_capable(ctlr, cap)	\

-- 
2.47.0