[PATCH v3 1/3] spi: spi-mem: add automatic poll status functions

patrice.chotard
2021-05-18T09:42:32Z

From: Patrice Chotard <patrice.chotard@foss.st.com>

With STM32 QSPI, it is possible to poll the status register of the device.
This could be done to offload the CPU during an operation (erase or
program a SPI NAND for example).

spi_mem_poll_status API has been added to handle this feature.
This new function take care of the offload/non-offload cases.

For the non-offload case, use read_poll_timeout() to poll the status in
order to release CPU during this phase.
For example, previously, when erasing large area, in non-offload case,
CPU load can reach ~50%, now it decrease to ~35%.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
---
Changes in v3:
- Add spi_mem_read_status() which allows to read 8 or 16 bits status.
- Add initial_delay_us and polling_delay_us parameters to spi_mem_poll_status()
and also to poll_status() callback.
- Move spi_mem_supports_op() in SW-based polling case.
- Add delay before invoking read_poll_timeout().
- Remove the reinit/wait_for_completion() added in v2.

Changes in v2:
- Indicates the spi_mem_poll_status() timeout unit
- Use 2-byte wide status register
- Add spi_mem_supports_op() call in spi_mem_poll_status()
- Add completion management in spi_mem_poll_status()
- Add offload/non-offload case management in spi_mem_poll_status()
- Optimize the non-offload case by using read_poll_timeout()

drivers/spi/spi-mem.c | 85 +++++++++++++++++++++++++++++++++++++
include/linux/spi/spi-mem.h | 14 ++++++
2 files changed, 99 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 1513553e4080..257dc501d5df 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -6,6 +6,7 @@
* Author: Boris Brezillon <boris.brezillon@bootlin.com>
*/
#include <linux/dmaengine.h>
+#include <linux/iopoll.h>
#include <linux/pm_runtime.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi-mem.h>
@@ -743,6 +744,89 @@ static inline struct spi_mem_driver *to_spi_mem_drv(struct device_driver *drv)
return container_of(drv, struct spi_mem_driver, spidrv.driver);
}

+int spi_mem_read_status(struct spi_mem *mem,
+ const struct spi_mem_op *op,
+ u16 *status)
+{
+ const u8 *bytes = (u8 *)op->data.buf.in;
+ int ret;
+
+ ret = spi_mem_exec_op(mem, op);
+ if (ret)
+ return ret;
+
+ if (op->data.nbytes > 1)
+ *status = ((u16)bytes[0] << 8) | bytes[1];
+ else
+ *status = bytes[0];
+
+ return 0;
+}
+
+/**
+ * spi_mem_poll_status() - Poll memory device status
+ * @mem: SPI memory device
+ * @op: the memory operation to execute
+ * @mask: status bitmask to ckeck
+ * @match: (status & mask) expected value
+ * @initial_delay_us: delay in us before starting to poll
+ * @polling_delay_us: time to sleep between reads in us
+ * @timeout_ms: timeout in milliseconds
+ *
+ * This function send a polling status request to the controller driver
+ *
+ * Return: 0 in case of success, -ETIMEDOUT in case of error,
+ * -EOPNOTSUPP if not supported.
+ */
+int spi_mem_poll_status(struct spi_mem *mem,
+ const struct spi_mem_op *op,
+ u16 mask, u16 match,
+ unsigned long initial_delay_us,
+ unsigned long polling_delay_us,
+ u16 timeout_ms)
+{
+ struct spi_controller *ctlr = mem->spi->controller;
+ int ret = -EOPNOTSUPP;
+ int read_status_ret;
+ u16 status;
+
+ if (op->data.nbytes < 1 || op->data.nbytes > 2)
+ return -EINVAL;
+
+ if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
+ ret = spi_mem_access_start(mem);
+ if (ret)
+ return ret;
+
+ ret = ctlr->mem_ops->poll_status(mem, op, mask, match,
+ initial_delay_us, polling_delay_us,
+ timeout_ms);
+
+ spi_mem_access_end(mem);
+ }
+
+ if (ret == -EOPNOTSUPP) {
+ if (!spi_mem_supports_op(mem, op))
+ return ret;
+
+ if (initial_delay_us < 10)
+ udelay(initial_delay_us);
+ else
+ usleep_range((initial_delay_us >> 2) + 1,
+ initial_delay_us);
+
+ ret = read_poll_timeout(spi_mem_read_status, read_status_ret,
+ (read_status_ret || ((status) & mask) == match),
+ polling_delay_us, timeout_ms * 1000, false, mem,
+ op, &status);
+ if (read_status_ret)
+ return read_status_ret;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(spi_mem_poll_status);
+
static int spi_mem_probe(struct spi_device *spi)
{
struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);
@@ -763,6 +847,7 @@ static int spi_mem_probe(struct spi_device *spi)
if (IS_ERR_OR_NULL(mem->name))
return PTR_ERR_OR_ZERO(mem->name);

+ init_completion(&ctlr->xfer_completion);
spi_set_drvdata(spi, mem);

return memdrv->probe(mem);
diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
index 2b65c9edc34e..10375d9ad747 100644
--- a/include/linux/spi/spi-mem.h
+++ b/include/linux/spi/spi-mem.h
@@ -250,6 +250,7 @@ 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.
+ * @poll_status: poll memory device status
*
* This interface should be implemented by SPI controllers providing an
* high-level interface to execute SPI memory operation, which is usually the
@@ -274,6 +275,12 @@ 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);
+ int (*poll_status)(struct spi_mem *mem,
+ const struct spi_mem_op *op,
+ u16 mask, u16 match,
+ unsigned long initial_delay_us,
+ unsigned long polling_rate_us,
+ unsigned long timeout_ms);
};

/**
@@ -369,6 +376,13 @@ devm_spi_mem_dirmap_create(struct device *dev, struct spi_mem *mem,
void devm_spi_mem_dirmap_destroy(struct device *dev,
struct spi_mem_dirmap_desc *desc);

+int spi_mem_poll_status(struct spi_mem *mem,
+ const struct spi_mem_op *op,
+ u16 mask, u16 match,
+ unsigned long initial_delay_us,
+ unsigned long polling_delay_us,
+ u16 timeout);
+
int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
struct module *owner);

--
2.17.1