Message-Id: <A89A87E2-E4C4-4DD7-9E51-9FD38D93DC0E@gmail.com>
Date:	Tue, 3 May 2011 10:13:10 -0400
From:	Jean-Francois Dagenais <jeff.dagenais@...il.com>
To:	Jonathan Cameron <jic23@....ac.uk>, Barry Song <21cnbao@...il.com>,
	linux-kernel@...r.kernel.org,
	device-drivers-devel@...ckfin.uclinux.org,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	linux-input@...r.kernel.org
Cc:	Yves.Lapointe@...log.com, Adrian.Flanagan@...log.com,
	Susan.Pratt@...log.com
Subject: Re: ad714x driver help and possible bug


On Apr 29, 2011, at 5:55, Jonathan Cameron wrote:

> Cc'd input, and analog devices driver list...
> 
> On 04/28/11 19:17, Jean-Francois Dagenais wrote:
>> Hi all,
>> 
>> I am having trouble getting the ad714x (i2c) driver to work in my
>> test setup. I am using the VGA i2c bus to talk to the ad7147 I have.
>> I used INTA of a PCI ethernet slot in my PC. I enabled the PCI device
>> without the driver module loaded.  I then give the interrupt number
>> to ad714x through the struct i2c_board_info. I actually tried the
>> same setup on two PCs, one intel graphics, the other nvidia to
>> eliminate the i2c master as a possible cause of my problem.
>> 
>> The device is successfully loaded and I can see the interrupts going.
>> The eventN device created under /dev/input never spit out anything
>> and so I added printks in the threaded ISR handler to see what is
>> going on.
>> 
>> I only have a wheel with 8 stages. In ad714x_wheel_state_machine() I
>> see that upon the first interrupt, the state goes from IDLE to
>> JITTER. After this the JITTER case checks that c_state == mask (with
>> mask being 0xff in our case). This condition is never met and the
>> driver stays indefinitely in this state. After lifting my finger from
>> the wheel, the chip settles down to scanning every so many
>> milliseconds.
>> 
>> The STAGE_COMPLETE_INT_STATUS is always 0 when my finger is off, but
>> varies a lot while my finger is on (while interrupt frequency is
>> high). Looking at the value of STAGE_COMPLETE_INT_STATUS in binary
>> reveals that the set bits are always in groups, e.g. 0x0007 or 0x001C
>> or 0x0081(I imagine a roll-over of our start_stage-end_stage (0-7)).
>> There seems to be a timing aspect here. I added a spin counter in the
>> threaded ISR to delay reading the 3 registers and that seemed to make
>> the c_state change a little.
>> 
>> I modified the code that reads the 3 registers right after the
>> mutex_lock in ad714x_interrupt_thread so that the
>> STAGE_COMPLETE_INT_STATUS is read before the other two (LOW and HIGH
>> regs). The result was surprising. The COMPLETE reg did read 0xff now
>> and the JITTER case went past the "if(c_state == mask)" but later
>> crashed (divide by 0) in ad714x_wheel_cal_abs_pos() called from the
>> JITTER case.
>> 
>> 
>> Here's the initial configuration I give the driver:
>> 
>> static struct ad714x_wheel_plat wheel_platform_data = {
>> 	.start_stage = 0, // int start_stage;
>> 	.end_stage = 7, // int end_stage;
>> 	.max_coord = 128,  // int max_coord;
>> };
>> 
>> static struct ad714x_platform_data wheel_dev_platform_data = {
>> 	.slider_num = 0,
>> 	.wheel_num = 1,
>> 	.touchpad_num = 0,
>> 	.button_num = 0,
>> 	.slider = 0,
>> 	.wheel = &wheel_platform_data, // struct ad714x_wheel_plat *wheel;
>> 	.touchpad = 0, // struct ad714x_touchpad_plat *touchpad;
>> 	.button = 0, // struct ad714x_button_plat *button;
>> 	.stage_cfg_reg =  { /* unsigned short stage_cfg_reg[STAGE_NUM][STAGE_CFGREG_NUM] */
>> 		{0xfffe, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xfffb, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xffef, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xffbf, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xfeff, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xfbff, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xefff, 0x3fff, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 		{0xffff, 0x3ffe, 0, 0x2626, 0x3e8, 0x3e8, 0x1388, 0x1388 },
>> 
>> 		{0xffff, 0x3fff, 0, 0x0606, 0x01f4, 0x01f4, 0x0320, 0x0320},
>> 		{0xffff, 0x3fff, 0, 0x0606, 0x01f4, 0x01f4, 0x0320, 0x0320},
>> 		{0xffff, 0x3fff, 0, 0x0606, 0x01f4, 0x01f4, 0x0320, 0x0320},
>> 		{0xffff, 0x3fff, 0, 0x0606, 0x01f4, 0x01f4, 0x0320, 0x0320},
>> 	},
>> 	.sys_cfg_reg = {0x027e, 0x00ff, 0x3233, 0x0819, 0x0832, 0x0000, 0x00ff, 0}, /* unsigned short sys_cfg_reg[SYS_CFGREG_NUM] */
>> 	//.sys_cfg_reg = {0x2b2, 0xfff, 0x3233, 0x819, 0x832, 0xcff, 0xcff, 0x0}, /* unsigned short sys_cfg_reg[SYS_CFGREG_NUM] */
>> };
>> 
> 
>> 
>> I also had to change the request_threaded_irq flags to specify
>> IRQF_ONESHOT so the kernel keeps the interrupt masked while we are
>> running ad714x_interrupt_thread(). Otherwise we were getting storms
>> of interrupts each time only one was requested. I am wondering if
>> this should be pulled back to the mainline kernel?
>> 
>> Thanks for pointers and clues!
>> 
> 
here's the printk I added to ad714x_wheel_state_machine()

	mask = ((1 << (hw->end_stage + 1)) - 1) - ((1 << hw->start_stage) - 1);

	h_state = ad714x->h_state & mask;
	c_state = ad714x->c_state & mask;
	dev_dbg(ad714x->dev, "interrupt state:%d mask:0x%x l:0x%x h:0x%x c:0x%x\n", 
		sw->state, 
		(u32)mask, 
		(u32)ad714x->l_state, 
		(u32)ad714x->h_state, 
		(u32)ad714x->c_state);

Here what it looks like upon loading a module which does the i2c_new_device of the AD7147:

<7>[58302.186886] my-pci-stub 0000:01:04.0: claimed by my platform module PCI stub
<6>[58302.186903] my-pci-stub 0000:01:04.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
<6>[58302.189815] ad714x_captouch 9-002c: found AD7147(A) captouch, rev:1
<6>[58302.427237] input: Unspecified device as /devices/virtual/input/input8

[ pause here while my hand goes from my mouse and keyboard to the wheel on the AD7147 ]

<7>[58311.646183] ad714x_captouch 9-002c: interrupt state:0 mask:0xff l:0x0 h:0x18 c:0x1c
<7>[58311.646192] ad714x_captouch 9-002c: case IDLE in if
<7>[58311.655436] ad714x_captouch 9-002c: wheel 0 touched
<7>[58311.663087] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x18 c:0x7
<7>[58311.674562] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x18 c:0x81
<7>[58311.686803] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x18 c:0x81
<7>[58311.699147] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x18 c:0x81
<7>[58311.711430] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x18 c:0x81
<7>[58311.723585] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x18 c:0x81
<7>[58311.736017] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x81
<7>[58311.748298] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x81
<7>[58311.760581] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x81
<7>[58311.772800] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x81
<7>[58311.785176] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x81
<7>[58311.797473] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x81
<7>[58311.809651] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x10 c:0x81

[ here I lift my finger ]

<7>[58311.822059] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.834345] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.846582] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.858800] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.871212] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.883517] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.895802] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.908099] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.920381] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58311.932585] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81

[...]

<7>[58313.432218] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81
<7>[58314.157343] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x81

[... after 2 seconds or so, the rhythm slows down to 2 interrupts per second or so ]

<7>[58314.169629] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x80

<7>[58314.976518] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x80

<7>[58315.783342] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x0 c:0x80


There is a clue in what I did next. I added a wait time in the isr thread function like so:

static irqreturn_t ad714x_interrupt_thread(int irq, void *data)
{
	struct ad714x_chip *ad714x = data;
	volatile int i;

	mutex_lock(&ad714x->mutex);

	i=0xffffff;
	while(i)
		--i;

	ad714x->read(ad714x->dev, STG_LOW_INT_STA_REG, &ad714x->l_state);
	ad714x->read(ad714x->dev, STG_HIGH_INT_STA_REG, &ad714x->h_state);
	ad714x->read(ad714x->dev, STG_COM_INT_STA_REG, &ad714x->c_state);
[ ... ]

this changes the above trace to these values:

while touching the wheel:
<7>[63085.414268] ad714x_captouch 9-002c: interrupt state:0 mask:0xff l:0x0 h:0x70 c:0x60
<7>[63085.414277] ad714x_captouch 9-002c: case IDLE in if
<7>[63085.423519] ad714x_captouch 9-002c: wheel 0 touched
<7>[63085.578931] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x70 c:0x18
<7>[63085.736079] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x70 c:0x3
<7>[63085.832304] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x70 c:0x60
<7>[63086.938334] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x30 c:0x60
<7>[63087.030835] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x60
<7>[63087.122909] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x60
<7>[63087.215014] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x60
<7>[63087.307071] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x60
<7>[63087.399367] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x60
<7>[63087.739386] ad714x_captouch 9-002c: interrupt state:1 mask:0xff l:0x0 h:0x38 c:0x83

Again, notice the state going from 0 (IDLE) to 1(JITTER), and never entering the "if" in the JITTER case (needs mask == c_state).  The HIGH register varies a lot while I move my finger around, but the COMPLETE looks like its always going and being cleared. I mentioned before that reading the COMPLETE status reg before the LOW and HIGH produces completely different results.

I am suspecting the register configuration we use is off somehow, I will review them thoroughly. Aside from this we are running out of leads here, anyone has input on this?

Thanks in advance!
JFD



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