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

[Michael Walle]

Hi Pratyush,

Am 2021-03-11 20:12, schrieb Pratyush Yadav:

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.ya...@ti.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);

Can't a calibration fail?

+       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);

--
-michael