On Fri, Apr 20, 2018 at 09:42:07PM +0200, Sebastian Reichel wrote: > On Fri, Apr 20, 2018 at 02:44:02PM -0300, Ezequiel Garcia wrote: > > Hi Sebastian, > > > > On Fri, 2018-04-20 at 19:24 +0200, Sebastian Reichel wrote: > > > The current reset-gpio support triggers an interrupt storm on platforms > > > using the maxtouch with level based interrupt. The Motorola Droid 4, > > > which I used for some of the tests is not affected, since it uses a level > > > based interrupt. > > > > > > > I found this confusing. Interrupt storm happen with level-based interrupts, > > but the Droid4 is not affected? Can I ask what happens during the interrupt storm. Are you getting lots of the "failed to read T44 and T5" message, or something else? > > > This change avoids the interrupt storm by enabling the device while > > > its interrupt is disabled. The following mxt_initialize() requires, > > > that the device is responsive (at least mxt224E is unresponsive for > > > ~22ms), so we wait some time. We don't wait for leaving bootloader > > > mode anymore, since mxt_initialize() checks for it anyways. > > > > > > > IMHO, having some more or less arbritrary sleeps is almost > > always a problem. This value might be enough for some platform, > > might be too short for some other, and then it might get too large > > for someone else. > > The 22ms chip-being-unresponsive are not newly introduced. The > same 22ms are also required for soft-reset. I did introduce a > new time (MXT_RESET_GPIO_TIME) for the "chip being reset" state, > since my randomly chosen 200ms from before were exaggerated > considering all mxt datasheets I checked stated only a few nano > seconds. According to the data sheets there is a period after a reset where the CHG line is temporarily set as an input, during which the host should ignore it. If you don't, you might get a stray interrupt and try and communicate with the device, which might leave it in a bad state. I think you mentioned that later in your email. The reset time varies per chip, but the 100ms in mxt_soft_reset() was based on discussions with app support at Atmel, so should be correct in most cases. -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
