Hi Wolfram,
On 06/02/2014 06:31 PM, Wolfram Sang wrote:
On Fri, May 16, 2014 at 05:32:10PM +0200, Maxime COQUELIN wrote:
The i2c timing values specified in the driver are the minimun
values defined in the I2C specifications.
The I2C specification does not specify any default or maximum values.
Some I2C devices are out of spec, and might not work properly with minimum
values.
Can you give names here? Would be interesting to know since a few
drivers implement the minimum timings.
I don't have the name actually.
The request to implement this change came from hw guys.
This patch adds a 10% margin on all the timings.
Is there a safety margin or do the devices start to work exactly at 10%?
10% is a safety margin, I don't know what is the limit.
Signed-off-by: Maxime Coquelin <maxime.coquelin@xxxxxx>
---
drivers/i2c/busses/i2c-st.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/drivers/i2c/busses/i2c-st.c b/drivers/i2c/busses/i2c-st.c
index 8720161..09142f1 100644
--- a/drivers/i2c/busses/i2c-st.c
+++ b/drivers/i2c/busses/i2c-st.c
@@ -210,21 +210,21 @@ static inline void st_i2c_clr_bits(void __iomem *reg, u32 mask)
static struct st_i2c_timings i2c_timings[] = {
That needs a comment about the margin, otherwise people will wonder
where these values come from.
Ok, I will add a comment in the v2.
[I2C_MODE_STANDARD] = {
.rate = 100000,
- .rep_start_hold = 4000,
- .rep_start_setup = 4700,
- .start_hold = 4000,
- .data_setup_time = 250,
- .stop_setup_time = 4000,
- .bus_free_time = 4700,
+ .rep_start_hold = 4400,
+ .rep_start_setup = 5170,
+ .start_hold = 4400,
+ .data_setup_time = 275,
+ .stop_setup_time = 4400,
+ .bus_free_time = 5170,
},
[I2C_MODE_FAST] = {
.rate = 400000,
- .rep_start_hold = 600,
- .rep_start_setup = 600,
- .start_hold = 600,
- .data_setup_time = 100,
- .stop_setup_time = 600,
- .bus_free_time = 1300,
+ .rep_start_hold = 660,
+ .rep_start_setup = 660,
+ .start_hold = 660,
+ .data_setup_time = 110,
+ .stop_setup_time = 660,
+ .bus_free_time = 1430,
},
};
--
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
