Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755655AbbHCVES (ORCPT ); Mon, 3 Aug 2015 17:04:18 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:34492 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754533AbbHCVEQ (ORCPT ); Mon, 3 Aug 2015 17:04:16 -0400 Date: Mon, 3 Aug 2015 14:04:09 -0700 From: Dmitry Torokhov To: maitysanchayan@gmail.com Cc: Stefan Agner , linux-input@vger.kernel.org, devicetree@vger.kernel.org, mark.rutland@arm.com, pawel.moll@arm.com, ijc+devicetree@hellion.org.uk, linux-kernel@vger.kernel.org, robh+dt@kernel.org, kernel@pengutronix.de, galak@codeaurora.org, shawn.guo@linaro.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 3/4] touchscreen: colibri-vf50-ts: Add touchscreen support for Colibri VF50 Message-ID: <20150803210409.GG38878@dtor-ws> References: <26748bd9a7bde7c2304b6b971f1150bb575e4938.1437058481.git.maitysanchayan@gmail.com> <20150717234242.GJ39282@dtor-ws> <40d7c372e64c7f25b7df3e48930386de@agner.ch> <20150721172044.GC39076@dtor-ws> <20150803152544.GA9716@Sanchayan-Arch.toradex.int> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150803152544.GA9716@Sanchayan-Arch.toradex.int> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5490 Lines: 137 Hi Sanchayan, On Mon, Aug 03, 2015 at 08:55:44PM +0530, maitysanchayan@gmail.com wrote: > Hello Dmitry, > > On 15-07-21 10:20:44, Dmitry Torokhov wrote: > > Hi Stefan, > > > > On Tue, Jul 21, 2015 at 04:43:36PM +0200, Stefan Agner wrote: > > > Hi Dmitry, > > > > > > As the original author of the driver I have some remarks to your review > > > > > > On 2015-07-18 01:42, Dmitry Torokhov wrote: > > > >> + /* > > > >> + * If touch pressure is too low, stop measuring and reenable > > > >> + * touch detection > > > >> + */ > > > >> + if (val_p < min_pressure || val_p > 2000) > > > >> + break; > > > > > > This is where the modules touch pressure is used to stop the measurement > > > process and switch back to interrupt mode. See my remarks at the end. > > > > > > >> + > > > >> + /* > > > >> + * The pressure may not be enough for the first x and the > > > >> + * second y measurement, but, the pressure is ok when the > > > >> + * driver is doing the third and fourth measurement. To > > > >> + * take care of this, we drop the first measurement always. > > > >> + */ > > > >> + if (discard_val_on_start) { > > > >> + discard_val_on_start = false; > > > >> + } else { > > > >> + /* > > > >> + * Report touch position and sleep for > > > >> + * next measurement > > > >> + */ > > > >> + input_report_abs(vf50_ts->ts_input, > > > >> + ABS_X, VF_ADC_MAX - val_x); > > > >> + input_report_abs(vf50_ts->ts_input, > > > >> + ABS_Y, VF_ADC_MAX - val_y); > > > >> + input_report_abs(vf50_ts->ts_input, > > > >> + ABS_PRESSURE, val_p); > > > >> + input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1); > > > >> + input_sync(vf50_ts->ts_input); > > > >> + } > > > >> + > > > >> + msleep(10); > > > >> + } > > > >> + > > > >> + /* Report no more touch, reenable touch detection */ > > > >> + input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0); > > > >> + input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0); > > > >> + input_sync(vf50_ts->ts_input); > > > >> + > > > >> + vf50_ts_enable_touch_detection(vf50_ts); > > > >> + > > > >> + /* Wait for the pull-up to be stable on high */ > > > >> + msleep(10); > > > >> + > > > >> + /* Reenable IRQ to detect touch */ > > > >> + enable_irq(vf50_ts->pen_irq); > > > >> + > > > >> + dev_dbg(dev, "Reenabled touch detection interrupt\n"); > > > >> +} > > > >> + > > > >> +static irqreturn_t vf50_ts_touched(int irq, void *dev_id) > > > >> +{ > > > >> + struct vf50_touch_device *vf50_ts = (struct vf50_touch_device *)dev_id; > > > >> + struct device *dev = &vf50_ts->pdev->dev; > > > >> + > > > >> + dev_dbg(dev, "Touch detected, start worker thread\n"); > > > >> + > > > >> + disable_irq_nosync(irq); > > > >> + > > > >> + /* Disable the touch detection plates */ > > > >> + gpiod_set_value(vf50_ts->gpio_ym, 0); > > > >> + > > > >> + /* Let the platform mux to default state in order to mux as ADC */ > > > >> + pinctrl_pm_select_default_state(dev); > > > >> + > > > >> + queue_work(vf50_ts->ts_workqueue, &vf50_ts->ts_work); > > > > > > > > If you convert this to a threaded interrupt you won't need to > > > > disable/reenable interrupt or queue work. You should also be able to use > > > > gpiod_set_value_cansleep() extending the range of ways the controller > > > > could be connected to systems. > > > > > > > > > > I'm not sure if a threaded interrupt is the right thing here. While the > > > pen is on the touchscreen (which can be for several seconds) > > > measurements have to be made in a continuous loop. Is it ok for a > > > threaded interrupt to run that long? > > > > Yes, why not? Threaded interrupt is simply a kernel thread that is woken > > when hard interrupt handler tells it to wake up. Very similar to > > interrupt + work queue, except that the kernel manages interactions > > properly for you. There are several drivers in kernel that do that, for > > example auo-pixcir-ts.c or tsc2007.c > > > > > > > > I'm also not sure if it is really safe to _not_ disable the pen down > > > GPIO interrupt. If we get a interrupt while measuring, we should ignore > > > that interrupt. > > > > The interrupt management core (you'll have to annotate it as > > IRQF_ONESHOT) will make sure it stays masked properly until the threaded > > handler completes so you do not need to disable it explicitly. > > After working some more on threaded irq implementation, if IRQ_ONESHOT > flag is used while requesting threaded irq, on entering the IRQ handler > the vf610_gpio_irq_mask is not called and vf610_gpio_irq_unmask is not > called on exiting the thread function, not something we expected. > > In contrast, using explicit disable_irq_nosync and enable_irq in the IRQ > handler and thread respectively results in the respective mask and unmask > function being called. > > The vf610_gpio_irq_*mask functions are in the gpio driver for Vybrid in > drivers/gpio/gpio-vf610.c. Well, for edge interrupts we normally do not mask/unmask IRQ as we expect the controller to latch onto the state and not re-raise intil interrupt is acked and I believe goes through edge condition again. For level-triggered IRQs we do mask the interrupt line. See kernel/irq/handle.c::handle_level_irq() and handle_edge_irq(). Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/