[PATCH v3 1/3] mtd: rawnand: Provide helper for polling GPIO R/B pin

Janusz Krzysztofik
2018-10-15T19:40:08Z

Each controller driver having access to NAND R/B pin over GPIO would
have to reimplement the polling loop otherwise.

Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
---
Changelog:
v3:
- don't surround added code with #ifdef CONFIG_GPIOLIB - sugeested by
Boris Brezillon - thanks,
- drop inadequate comment on calling ->exec_op() recursively - catched
by Boris Brezillon, thanks,
- drop redundant commend from header file - suggensted by Boris
Brezillon - thanks,
- update comment on waiting for R/B pin rather than command completion
v2:
New patch - v1 consisted of only one patch reusing legacy helper

drivers/mtd/nand/raw/nand_base.c | 31 +++++++++++++++++++++++++++++++
include/linux/mtd/rawnand.h | 4 ++++
2 files changed, 35 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 05bd0779fe9b..0d5a2dc59b8d 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -45,6 +45,7 @@
#include <linux/io.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>
+#include <linux/gpio/consumer.h>

#include "internals.h"

@@ -531,6 +532,36 @@ int nand_soft_waitrdy(struct nand_chip *chip, unsigned long timeout_ms)
};
EXPORT_SYMBOL_GPL(nand_soft_waitrdy);

+/**
+ * nand_gpio_waitrdy - Poll R/B GPIO pin until ready
+ * @chip: NAND chip structure
+ * @gpiod: GPIO descriptor of R/B pin
+ * @timeout_ms: Timeout in ms
+ *
+ * Poll the R/B GPIO pin until it becomes ready. If that does not happen
+ * whitin the specified timeout, -ETIMEDOUT is returned.
+ *
+ * This helper is intended to be used when the controller has access to the
+ * NAND R/B pin over GPIO.
+ *
+ * Return 0 if the R/B pin indicates chip is ready, a negative error otherwise.
+ */
+int nand_gpio_waitrdy(struct nand_chip *chip, struct gpio_desc *gpiod,
+ unsigned long timeout_ms)
+{
+ /* Wait until R/B pin indicates chip is ready or timeout occurs */
+ timeout_ms = jiffies + msecs_to_jiffies(timeout_ms);
+ do {
+ if (gpiod_get_value_cansleep(gpiod))
+ return 0;
+
+ cond_resched();
+ } while (time_before(jiffies, timeout_ms));
+
+ return gpiod_get_value_cansleep(gpiod) ? 0 : -ETIMEDOUT;
+};
+EXPORT_SYMBOL_GPL(nand_gpio_waitrdy);
+
/**
* panic_nand_get_device - [GENERIC] Get chip for selected access
* @chip: the nand chip descriptor
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index e10b126e148f..4e91a70ede10 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -1346,4 +1346,8 @@ void nand_release(struct nand_chip *chip);
*/
int nand_soft_waitrdy(struct nand_chip *chip, unsigned long timeout_ms);

+struct gpio_desc;
+int nand_gpio_waitrdy(struct nand_chip *chip, struct gpio_desc *gpiod,
+ unsigned long timeout_ms);
+
#endif /* __LINUX_MTD_RAWNAND_H */
--
2.16.4