[PATCH/RFC 0/2] Add power supply switch in platform data

[PATCH/RFC 0/2] Add power supply switch in platform data

[Stanimir Varbanov]

Hi,

Here are two patches that add a power method in flash platform data
for chips power control. The first patch adding this function and
the second use it in m25p driver.

Comments are welcome !

Stanimir Varbanov (2):
  spi: flash: Add power method into flash platform data
  mtd: m25p80: Call a platform power method in the driver

 drivers/mtd/devices/m25p80.c |   41 +++++++++++++++++++++++++++++++++++++----
 include/linux/spi/flash.h    |    4 ++++
 2 files changed, 41 insertions(+), 4 deletions(-)

-- 
1.7.4.1


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[PATCH/RFC 1/2] spi: flash: Add power method into flash platform data

[Stanimir Varbanov]

For embedded devices or devices sensible to the power consumption
is reasonable to have a way to control the flash chips power. This
change in flash_platform_data makes possible to control the power
supply of the flash memory chip by adding a "power" method to it.

The platform then could attach a callback and control power supply
by it's choice. For example by other regulator driver, GPIO or
do nothing.

Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
---
 include/linux/spi/flash.h |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/include/linux/spi/flash.h b/include/linux/spi/flash.h
index 3f22932..045a6fc 100644
--- a/include/linux/spi/flash.h
+++ b/include/linux/spi/flash.h
@@ -10,6 +10,7 @@ struct mtd_partition;
  * @nr_parts: number of mtd_partitions for static partitoning
  * @type: optional flash device type (e.g. m25p80 vs m25p64), for use
  *	with chips that can't be queried for JEDEC or other IDs
+ * @power: method called to enable or disable Vcc
  *
  * Board init code (in arch/.../mach-xxx/board-yyy.c files) can
  * provide information about SPI flash parts (such as DataFlash) to
@@ -26,6 +27,9 @@ struct flash_platform_data {
 	char		*type;
 
 	/* we'll likely add more ... use JEDEC IDs, etc */
+
+	/* on = 0 disable Vcc, on != 0 enable Vcc */
+	void (*power)(int on);
 };
 
 #endif
-- 
1.7.4.1


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[PATCH/RFC 2/2] mtd: m25p80: Call a platform power method in the driver

[Stanimir Varbanov]

On some devices the flash chip could be powered off when m25p driver
is probed. To avoid erroneous detection the power of the chip must be
turn on, add a power function in m25p_probe to switch on the power by
platform data. The power will be turned off at the probe end.

Also implement a get/put_device callbacks to power on/off the flash
chip.

Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
---
 drivers/mtd/devices/m25p80.c |   41 +++++++++++++++++++++++++++++++++++++----
 1 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index e6ba034..6ab5896 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -806,6 +806,27 @@ static const struct spi_device_id *__devinit jedec_probe(struct spi_device *spi)
 	return ERR_PTR(-ENODEV);
 }
 
+static void m25p_power(struct flash_platform_data *pdata, int on)
+{
+	if (pdata && pdata->power)
+		pdata->power(on);
+}
+
+static int m25p_get_device(struct mtd_info *mtd)
+{
+	struct flash_platform_data *pdata = mtd->dev.parent->platform_data;
+
+	m25p_power(pdata, 1);
+
+	return 0;
+}
+
+static void m25p_put_device(struct mtd_info *mtd)
+{
+	struct flash_platform_data *pdata = mtd->dev.parent->platform_data;
+
+	m25p_power(pdata, 0);
+}
 
 /*
  * board specific setup should have ensured the SPI clock used here
@@ -820,6 +841,7 @@ static int __devinit m25p_probe(struct spi_device *spi)
 	struct flash_info		*info;
 	unsigned			i;
 	struct mtd_part_parser_data	ppdata;
+	int				ret;
 
 	/* Platform data helps sort out which chip type we have, as
 	 * well as how this board partitions it.  If we don't have
@@ -845,12 +867,16 @@ static int __devinit m25p_probe(struct spi_device *spi)
 
 	info = (void *)id->driver_data;
 
+	/* power on device while probing */
+	m25p_power(data, 1);
+
 	if (info->jedec_id) {
 		const struct spi_device_id *jid;
 
 		jid = jedec_probe(spi);
 		if (IS_ERR(jid)) {
-			return PTR_ERR(jid);
+			ret = PTR_ERR(jid);
+			goto out;
 		} else if (jid != id) {
 			/*
 			 * JEDEC knows better, so overwrite platform ID. We
@@ -867,12 +893,15 @@ static int __devinit m25p_probe(struct spi_device *spi)
 	}
 
 	flash = kzalloc(sizeof *flash, GFP_KERNEL);
-	if (!flash)
-		return -ENOMEM;
+	if (!flash) {
+		ret = -ENOMEM;
+		goto out;
+	}
 	flash->command = kmalloc(MAX_CMD_SIZE + FAST_READ_DUMMY_BYTE, GFP_KERNEL);
 	if (!flash->command) {
 		kfree(flash);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto out;
 	}
 
 	flash->spi = spi;
@@ -902,6 +931,8 @@ static int __devinit m25p_probe(struct spi_device *spi)
 	flash->mtd.size = info->sector_size * info->n_sectors;
 	flash->mtd.erase = m25p80_erase;
 	flash->mtd.read = m25p80_read;
+	flash->mtd.get_device = m25p_get_device;
+	flash->mtd.put_device = m25p_put_device;
 
 	/* sst flash chips use AAI word program */
 	if (JEDEC_MFR(info->jedec_id) == CFI_MFR_SST)
@@ -956,6 +987,8 @@ static int __devinit m25p_probe(struct spi_device *spi)
 				flash->mtd.eraseregions[i].erasesize / 1024,
 				flash->mtd.eraseregions[i].numblocks);
 
+out:
+	m25p_power(data, 0);
 
 	/* partitions should match sector boundaries; and it may be good to
 	 * use readonly partitions for writeprotected sectors (BP2..BP0).
-- 
1.7.4.1


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Re: [PATCH/RFC 2/2] mtd: m25p80: Call a platform power method in the driver

[Baruch Siach]

Hi Stanimir,

On Thu, Aug 25, 2011 at 04:29:12PM +0300, Stanimir Varbanov wrote:
> On some devices the flash chip could be powered off when m25p driver
> is probed. To avoid erroneous detection the power of the chip must be
> turn on, add a power function in m25p_probe to switch on the power by
> platform data. The power will be turned off at the probe end.

[snip]

> +	/* power on device while probing */
> +	m25p_power(data, 1);

[snip]

> +out:
> +	m25p_power(data, 0);

Shouldn't you power off in m25p_remove() as well?

baruch

-- 
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Re: [PATCH/RFC 2/2] mtd: m25p80: Call a platform power method in the driver

[Stanimir Varbanov]

Hi, Baruch

Thanks for the comments !

Baruch Siach wrote:
> Hi Stanimir,
> 
> On Thu, Aug 25, 2011 at 04:29:12PM +0300, Stanimir Varbanov wrote:
>> On some devices the flash chip could be powered off when m25p driver
>> is probed. To avoid erroneous detection the power of the chip must be
>> turn on, add a power function in m25p_probe to switch on the power by
>> platform data. The power will be turned off at the probe end.
> 
> [snip]
> 
>> +	/* power on device while probing */
>> +	m25p_power(data, 1);
> 
> [snip]
> 
>> +out:
>> +	m25p_power(data, 0);
> 
> Shouldn't you power off in m25p_remove() as well?
> 

IMO, no, because m25p_power(off) is called from m25p_put_device(). Then 
m25p_put_device() is called from mtdchar::mtd_close(). m25p_remove must
fail if user didn't close mtdchar /dev/mtdX device.

The motivation to use power on/off in m25p_probe is because the flash 
chip might be not powered when driver probe is called. The chip is powered
on on the probe begging and powered off after JEDEC probe pass.

> baruch
> 

regards,
Stan

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