Hi, On Sat, Apr 21, 2018 at 09:11:37PM +0100, Nick Dyer wrote: > 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? I don't get any message (with DEBUG enabled for the driver). The boot process hangs and after a few seconds the watchdog kicks in. > > > > 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. Right. This sleep time is missing for the gpio based reset. The other checks are not required, since the chip initialization routine is called directly afterwards. I will send a PATCHv2, that fixes the patch description and uses the same timeout value for both resets. -- Sebastian
Attachment:
signature.asc
Description: PGP signature
