[RFC PATCH 01/10] spi: spi-mem: Introduce support for tuning controller

[Santhosh Kumar K]

From: Pratyush Yadav <pratyush@xxxxxxxxxx>

Some controllers like the Cadence OSPI controller need to perform a
tuning sequence to operate at high data rates. Tuning is needs to happen
once the device is switched to appropriate mode (say 8S-8S-8S or
8D-8D-8D). Add a hook that spi-mem client devices can call in order to tune
the controller to operate in a given mode and data rate.

This is somewhat similar to eMMC/SD tuning for higher speed modes like
HS200, but there isn't a standard specification around the same though.

Signed-off-by: Pratyush Yadav <pratyush@xxxxxxxxxx>
Signed-off-by: Santhosh Kumar K <s-k6@xxxxxx>
---
 drivers/spi/spi-mem.c       | 11 +++++++++++
 include/linux/spi/spi-mem.h |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 064b99204d9a..6c254291ee23 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -559,6 +559,17 @@ int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
 }
 EXPORT_SYMBOL_GPL(spi_mem_adjust_op_size);
 
+int spi_mem_execute_tuning(struct spi_mem *mem, const struct spi_mem_op *op)
+{
+	struct spi_controller *ctlr = mem->spi->controller;
+
+	if (!ctlr->mem_ops || !ctlr->mem_ops->execute_tuning)
+		return -EOPNOTSUPP;
+
+	return ctlr->mem_ops->execute_tuning(mem, op);
+}
+EXPORT_SYMBOL_GPL(spi_mem_execute_tuning);
+
 /**
  * spi_mem_adjust_op_freq() - Adjust the frequency of a SPI mem operation to
  *			      match controller, PCB and chip limitations
diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
index 82390712794c..639fee61251c 100644
--- a/include/linux/spi/spi-mem.h
+++ b/include/linux/spi/spi-mem.h
@@ -314,6 +314,12 @@ static inline void *spi_mem_get_drvdata(struct spi_mem *mem)
  * @poll_status: poll memory device status until (status & mask) == match or
  *               when the timeout has expired. It fills the data buffer with
  *               the last status value.
+ * @execute_tuning: perform PHY tuning to achieve high speed SPI operations.
+ *		    Should be called after the SPI memory device has been
+ *		    completely initialized. The op passed should contain a
+ *		    template for the read operation used for the device so the
+ *		    controller can decide what type of tuning is required
+ *		    for the type of read op passed.
  *
  * This interface should be implemented by SPI controllers providing an
  * high-level interface to execute SPI memory operation, which is usually the
@@ -344,6 +350,8 @@ struct spi_controller_mem_ops {
 			   unsigned long initial_delay_us,
 			   unsigned long polling_rate_us,
 			   unsigned long timeout_ms);
+	int (*execute_tuning)(struct spi_mem *mem,
+			      const struct spi_mem_op *op);
 };
 
 /**
@@ -423,6 +431,7 @@ bool spi_mem_default_supports_op(struct spi_mem *mem,
 #endif /* CONFIG_SPI_MEM */
 
 int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op);
+int spi_mem_execute_tuning(struct spi_mem *mem, const struct spi_mem_op *op);
 void spi_mem_adjust_op_freq(struct spi_mem *mem, struct spi_mem_op *op);
 u64 spi_mem_calc_op_duration(struct spi_mem *mem, struct spi_mem_op *op);
 
-- 
2.34.1