linux-kernel - [RFC PATCH 1/6] spi: spi-mem: Tell controller when device is ready for calibration

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Date:   Fri, 12 Mar 2021 00:42:11 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Michael Walle <michael@...le.cc>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mtd@...ts.infradead.org>, <linux-spi@...r.kernel.org>
CC:     Pratyush Yadav <p.yadav@...com>, Lokesh Vutla <lokeshvutla@...com>
Subject: [RFC PATCH 1/6] spi: spi-mem: Tell controller when device is ready for calibration

Some controllers like the Cadence OSPI controller need to perform a
calibration sequence to operate at high clock speeds. This calibration
should happen after the flash is fully initialized otherwise the
calibration might happen in a different SPI mode from the one the flash
is finally set to. Add a hook that can be used to tell the controller
when the flash is ready for calibration. Whether calibration is needed
depends on the controller.

Signed-off-by: Pratyush Yadav <p.yadav@...com>
---
 drivers/spi/spi-mem.c       | 12 ++++++++++++
 include/linux/spi/spi-mem.h |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index dc713b0c3c4d..e2f05ad3f4dc 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -464,6 +464,18 @@ 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_do_calibration(struct spi_mem *mem, struct spi_mem_op *op)
+{
+	struct spi_controller *ctlr = mem->spi->controller;
+
+	if (!ctlr->mem_ops || !ctlr->mem_ops->do_calibration)
+		return -EOPNOTSUPP;
+
+	ctlr->mem_ops->do_calibration(mem, op);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_mem_do_calibration);
+
 static ssize_t spi_mem_no_dirmap_read(struct spi_mem_dirmap_desc *desc,
 				      u64 offs, size_t len, void *buf)
 {
diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
index 2b65c9edc34e..97a2d280f2d0 100644
--- a/include/linux/spi/spi-mem.h
+++ b/include/linux/spi/spi-mem.h
@@ -250,6 +250,12 @@ static inline void *spi_mem_get_drvdata(struct spi_mem *mem)
  *		  the currently mapped area), and the caller of
  *		  spi_mem_dirmap_write() is responsible for calling it again in
  *		  this case.
+ * @do_calibration: perform calibration needed for high SPI clock speed
+ *		    operation. 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 calibration is
+ *		    required for this type of read.
  *
  * This interface should be implemented by SPI controllers providing an
  * high-level interface to execute SPI memory operation, which is usually the
@@ -274,6 +280,7 @@ struct spi_controller_mem_ops {
 			       u64 offs, size_t len, void *buf);
 	ssize_t (*dirmap_write)(struct spi_mem_dirmap_desc *desc,
 				u64 offs, size_t len, const void *buf);
+	void (*do_calibration)(struct spi_mem *mem, struct spi_mem_op *op);
 };
 
 /**
@@ -346,6 +353,7 @@ bool spi_mem_dtr_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_do_calibration(struct spi_mem *mem, struct spi_mem_op *op);
 
 bool spi_mem_supports_op(struct spi_mem *mem,
 			 const struct spi_mem_op *op);
-- 
2.30.0