[PATCH 2/2] m25p80: if supported put chip to deep power down if not used

[Heiner Kallweit]

Depending on the chip type the difference in power consumption between
standby and deep power down might be relevant for embedded devices.

This patch implements deep power down for few chip types. Most likely
more support this feature.

It was successfully tested on a i.mx6 based mini-pc with m25px16.

Signed-off-by: Heiner Kallweit <hkallweit1 at gmail.com>
---
 drivers/mtd/devices/m25p80.c | 112 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 111 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 85e3546..c1e1841 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -19,6 +19,7 @@
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/device.h>
+#include <linux/delay.h>
 
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
@@ -33,8 +34,22 @@ struct m25p {
 	struct spi_nor		spi_nor;
 	struct mtd_info		mtd;
 	u8			command[MAX_CMD_SIZE];
+	int			pm_list_index;
 };
 
+struct m25p_pm {
+	const char *name;
+	int (*resume)(struct spi_nor *nor, enum spi_nor_ops ops);
+	void (*suspend)(struct spi_nor *nor, enum spi_nor_ops ops);
+};
+
+#define PM_ENTRY(_n, _r, _s)		\
+	{				\
+		.name = (_n),		\
+		.resume = (_r),		\
+		.suspend = (_s),	\
+	}
+
 static int m25p80_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
 {
 	struct m25p *flash = nor->priv;
@@ -170,6 +185,70 @@ static int m25p80_erase(struct spi_nor *nor, loff_t offset)
 	return 0;
 }
 
+static inline int m25p_gen_resume(struct spi_nor *nor, unsigned long udelay)
+{
+	int ret;
+
+	ret = m25p80_write_reg(nor, 0xAB, NULL, 0, 0);
+	if (ret)
+		return ret;
+
+	if (udelay < 10)
+		udelay(udelay);
+	else
+		usleep_range(udelay, udelay + 10);
+
+	return 0;
+}
+
+static void m25p_gen_suspend(struct spi_nor *nor, enum spi_nor_ops ops)
+{
+	m25p80_write_reg(nor, 0xB9, NULL, 0, 0);
+}
+
+static int m25p_m25px16_resume(struct spi_nor *nor, enum spi_nor_ops ops)
+{
+	return m25p_gen_resume(nor, 30);
+}
+
+static int m25p_en25q64_resume(struct spi_nor *nor, enum spi_nor_ops ops)
+{
+	return m25p_gen_resume(nor, 3);
+}
+
+static int m25p_s25fl129p1_resume(struct spi_nor *nor, enum spi_nor_ops ops)
+{
+	return m25p_gen_resume(nor, 30);
+}
+
+static const struct m25p_pm m25p_pm_list[] = {
+	PM_ENTRY("m25px16",	m25p_m25px16_resume,	m25p_gen_suspend),
+	PM_ENTRY("en25q64",	m25p_en25q64_resume,	m25p_gen_suspend),
+	PM_ENTRY("s25fl129p1",	m25p_s25fl129p1_resume,	m25p_gen_suspend),
+};
+
+static int m25p80_resume(struct spi_nor *nor, enum spi_nor_ops ops)
+{
+	struct m25p *flash = nor->priv;
+	int idx = flash->pm_list_index;
+
+	if (idx == -1)
+		return 0;
+
+	return m25p_pm_list[idx].resume(nor, ops);
+}
+
+static void m25p80_suspend(struct spi_nor *nor, enum spi_nor_ops ops)
+{
+	struct m25p *flash = nor->priv;
+	int idx = flash->pm_list_index;
+
+	if (idx == -1)
+		return;
+
+	m25p_pm_list[idx].suspend(nor, ops);
+}
+
 /*
  * board specific setup should have ensured the SPI clock used here
  * matches what the READ command supports, at least until this driver
@@ -183,7 +262,7 @@ static int m25p_probe(struct spi_device *spi)
 	struct spi_nor *nor;
 	enum read_mode mode = SPI_NOR_NORMAL;
 	char *flash_name = NULL;
-	int ret;
+	int i, ret;
 
 	data = dev_get_platdata(&spi->dev);
 
@@ -199,6 +278,8 @@ static int m25p_probe(struct spi_device *spi)
 	nor->erase = m25p80_erase;
 	nor->write_reg = m25p80_write_reg;
 	nor->read_reg = m25p80_read_reg;
+	nor->prepare = m25p80_resume;
+	nor->unprepare = m25p80_suspend;
 
 	nor->dev = &spi->dev;
 	nor->mtd = &flash->mtd;
@@ -207,6 +288,7 @@ static int m25p_probe(struct spi_device *spi)
 	spi_set_drvdata(spi, flash);
 	flash->mtd.priv = nor;
 	flash->spi = spi;
+	flash->pm_list_index = -1;
 
 	if (spi->mode & SPI_RX_QUAD)
 		mode = SPI_NOR_QUAD;
@@ -230,6 +312,18 @@ static int m25p_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
+	/* look for power management hooks */
+	for (i = 0; i < ARRAY_SIZE(m25p_pm_list); i++) {
+		if (!strcmp(nor->chip_name, m25p_pm_list[i].name)) {
+			flash->pm_list_index = i;
+			break;
+		}
+	}
+	/* if supported go to deep power down
+	 * until somebody needs to access the flash
+	 */
+	m25p80_suspend(nor, SPI_NOR_OPS_READ);
+
 	ppdata.of_node = spi->dev.of_node;
 
 	return mtd_device_parse_register(&flash->mtd, NULL, &ppdata,
@@ -241,11 +335,26 @@ static int m25p_probe(struct spi_device *spi)
 static int m25p_remove(struct spi_device *spi)
 {
 	struct m25p	*flash = spi_get_drvdata(spi);
+	struct spi_nor  *nor = &flash->spi_nor;
+
+	m25p80_resume(nor, SPI_NOR_OPS_READ);
 
 	/* Clean up MTD stuff. */
 	return mtd_device_unregister(&flash->mtd);
 }
 
+/* wake up SPI NOR from deep power down
+ * else in case of reboot the boot loader might not be able
+ * to access the SPI NOR
+ */
+static void m25p_shutdown(struct spi_device *spi)
+{
+	struct m25p     *flash = spi_get_drvdata(spi);
+	struct spi_nor  *nor = &flash->spi_nor;
+
+	m25p80_resume(nor, SPI_NOR_OPS_READ);
+}
+
 /*
  * XXX This needs to be kept in sync with spi_nor_ids.  We can't share
  * it with spi-nor, because if this is built as a module then modpost
@@ -303,6 +412,7 @@ static struct spi_driver m25p80_driver = {
 	.id_table	= m25p_ids,
 	.probe	= m25p_probe,
 	.remove	= m25p_remove,
+	.shutdown = m25p_shutdown,
 
 	/* REVISIT: many of these chips have deep power-down modes, which
 	 * should clearly be entered on suspend() to minimize power use.
-- 
2.2.2