Re: [PATCH] Input: elants_i2c - Fix sw reset delays

On Fri, Aug 24, 2018 at 4:07 PM dbasehore . [off-list ref] wrote:

On Fri, Aug 24, 2018 at 1:49 AM Andi Shyti [off-list ref] wrote:

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Hi Derek,

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On Thu, Aug 23, 2018 at 04:10:13PM -0700, Derek Basehore wrote:

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We only need to wait 10ms instead of 30ms before starting fastboot or
sending IAP on the touchscreen. Also, instead of delaying everytime
sw_reset is called, this delays 10ms in the function that starts
fastboot. There's also an explicit 20ms delay before sending IAP when
updating the firmware, so no additional delay is needed there. This
change also has the benefit of not delaying when wakeup is enabled
during suspend. This is because sw_reset is called, yet fastboot
isn't.

...

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-       /*
-        * We should wait at least 10 msec (but no more than 40) before
-        * sending fastboot or IAP command to the device.
-        */
-       msleep(30);
-

moving from 30 to 0 is a bit alarming... what does the datasheet
say?

We're moving from 30msec to 10msec. We used to do this in an older kernel.

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Sometimes delays are implicit in the system where you are testing
the driver, so that without any msleep it might work in your
system but it might not on others.

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+             /*
+              * We should wait at least 10 msec (but no more than 40) before
+              * sending IAP command to the device.
+              */
              msleep(20);

I agree though that it's not nice to wait twice here (even though
as Dmitry says it doesn't hurt so much). Wouldn't it make more
sense to remove this msleep instead?
This way...

We still need this if the delay is removed from the sw_reset function. We have a total of 20msecs delayed between sw_reset and sending IAP in our old kernel which should be well tested. There seems to be no reason why the delays increased.

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+     /*
+      * We should wait at least 10 msec (but no more than 40) before sending
+      * fastboot command to the device.
+      */
+     usleep_range(10 * 1000, 11 * 1000);
+
      error = elants_i2c_send(client, boot_cmd, sizeof(boot_cmd));

... you do not need to add an extra sleep here.

I added it here since I removed the 30msec sleep in sw_reset. This prevents us from sleeping on resume when the touch controller is already on for wake up capabilities. This is the same delay that we have in our old 3.8 kernel, so it's pretty well tested and shipped in production.

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Andi

Resending since it seems my plain text setting was removed...