* [PATCH] i2c: busses: i2c-bcm2835: S-Register clear reserved bits
@ 2015-06-16 15:40 Silvan Wicki
[not found] ` <1434469259-6474-1-git-send-email-linux_wi-ADq4ffItWIY@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Silvan Wicki @ 2015-06-16 15:40 UTC (permalink / raw)
To: wsa-z923LK4zBo2bacvFa/9K2g
Cc: swarren-3lzwWm7+Weoh9ZMKESR00Q, linux-i2c-u79uwXL29TY76Z2rM5mHXA,
linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r,
linux_wi-ADq4ffItWIY
The Datasheet mentions on page 31 that the bits 10-31 must be read as
don't care and written as 0.
https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
We cannot guarantee that we reed bits 10-31 as always 0 (becuase the
datasheet says read as don't care). We clear the bits with a bitmask to
prevent writing back unknown data at the reserved bits.
Signed-off-by: Silvan Wicki <linux_wi-ADq4ffItWIY@public.gmane.org>
---
drivers/i2c/busses/i2c-bcm2835.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index c9336a3..aa06da1 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -50,6 +50,8 @@
#define BCM2835_I2C_S_CLKT BIT(9)
#define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */
+#define BCM2835_I2C_BITMSK_S 0x03FF
+
#define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
struct bcm2835_i2c_dev {
@@ -111,6 +113,7 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
u32 val, err;
val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
+ val &= BCM2835_I2C_BITMSK_S;
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
--
2.1.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] i2c: busses: i2c-bcm2835: S-Register clear reserved bits
[not found] ` <1434469259-6474-1-git-send-email-linux_wi-ADq4ffItWIY@public.gmane.org>
@ 2015-06-17 1:34 ` Stephen Warren
2015-06-17 12:10 ` Wolfram Sang
1 sibling, 0 replies; 3+ messages in thread
From: Stephen Warren @ 2015-06-17 1:34 UTC (permalink / raw)
To: Silvan Wicki, wsa-z923LK4zBo2bacvFa/9K2g
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA,
linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r
On 06/16/2015 09:40 AM, Silvan Wicki wrote:
> The Datasheet mentions on page 31 that the bits 10-31 must be read as
> don't care and written as 0.
> https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
>
> We cannot guarantee that we reed bits 10-31 as always 0 (becuase the
> datasheet says read as don't care). We clear the bits with a bitmask to
> prevent writing back unknown data at the reserved bits.
I guess that's true.
Acked-by: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] i2c: busses: i2c-bcm2835: S-Register clear reserved bits
[not found] ` <1434469259-6474-1-git-send-email-linux_wi-ADq4ffItWIY@public.gmane.org>
2015-06-17 1:34 ` Stephen Warren
@ 2015-06-17 12:10 ` Wolfram Sang
1 sibling, 0 replies; 3+ messages in thread
From: Wolfram Sang @ 2015-06-17 12:10 UTC (permalink / raw)
To: Silvan Wicki
Cc: swarren-3lzwWm7+Weoh9ZMKESR00Q, linux-i2c-u79uwXL29TY76Z2rM5mHXA,
linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r
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On Tue, Jun 16, 2015 at 05:40:59PM +0200, Silvan Wicki wrote:
> The Datasheet mentions on page 31 that the bits 10-31 must be read as
> don't care and written as 0.
> https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
>
> We cannot guarantee that we reed bits 10-31 as always 0 (becuase the
> datasheet says read as don't care). We clear the bits with a bitmask to
> prevent writing back unknown data at the reserved bits.
>
> Signed-off-by: Silvan Wicki <linux_wi-ADq4ffItWIY@public.gmane.org>
Applied to for-next, thanks!
If possible, use a spell checker on your commit message.
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2015-06-16 15:40 [PATCH] i2c: busses: i2c-bcm2835: S-Register clear reserved bits Silvan Wicki
[not found] ` <1434469259-6474-1-git-send-email-linux_wi-ADq4ffItWIY@public.gmane.org>
2015-06-17 1:34 ` Stephen Warren
2015-06-17 12:10 ` Wolfram Sang
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