From 5affb607720d734ca572b8a77c5c7d62d3042b6f Mon Sep 17 00:00:00 2001
From: Gregory Bean <gbean@codeaurora.org>
Date: Thu, 9 Sep 2010 16:38:02 -0700
Subject: gpio: sx150x: correct and refine reset-on-probe behavior
Replace the arbitrary software-reset call from the device-probe
method, because:
- It is defective. To work correctly, it should be two byte writes,
not a single word write. As it stands, it does nothing.
- Some devices with sx150x expanders installed have their NRESET pins
ganged on the same line, so resetting one causes the others to reset -
not a nice thing to do arbitrarily!
- The probe, usually taking place at boot, implies a recent hard-reset,
so a software reset at this point is just a waste of energy anyway.
Therefore, make it optional, defaulting to off, as this will match the
common case of probing at powerup and also matches the current broken
no-op behavior.
Signed-off-by: Gregory Bean <gbean@codeaurora.org>
Reviewed-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/i2c/sx150x.h | 4 ++++
1 file changed, 4 insertions(+)
(limited to 'include/linux/i2c')
diff --git a/include/linux/i2c/sx150x.h b/include/linux/i2c/sx150x.h
index ee3049cb9ba5..52baa79d69a7 100644
--- a/include/linux/i2c/sx150x.h
+++ b/include/linux/i2c/sx150x.h
@@ -63,6 +63,9 @@
* IRQ lines will appear. Similarly to gpio_base, the expander
* will create a block of irqs beginning at this number.
* This value is ignored if irq_summary is < 0.
+ * @reset_during_probe: If set to true, the driver will trigger a full
+ * reset of the chip at the beginning of the probe
+ * in order to place it in a known state.
*/
struct sx150x_platform_data {
unsigned gpio_base;
@@ -73,6 +76,7 @@ struct sx150x_platform_data {
u16 io_polarity;
int irq_summary;
unsigned irq_base;
+ bool reset_during_probe;
};
#endif /* __LINUX_I2C_SX150X_H */
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