linux-kernel - Re: [PATCH 3/5] i2c: omap: handle all irqs befor unblocking omap_i2c_xfer

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Date:	Wed, 19 Jun 2013 21:43:04 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	<balbi@...com>
CC:	Wolfram Sang <wsa@...-dreams.de>, Tony Lindgren <tony@...mide.com>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-i2c@...r.kernel.org>, Kevin Hilman <khilman@...aro.org>
Subject: Re: [PATCH 3/5] i2c: omap: handle all irqs befor unblocking omap_i2c_xfer_msg()

Hi Felipe,
On 06/07/2013 10:05 PM, Felipe Balbi wrote:
> Hi,
>
> On Fri, Jun 07, 2013 at 09:46:06PM +0300, Grygorii Strashko wrote:
>> ARDY|NACK and ARDY|AL are set together in OMAP_I2C_STAT_REG, which will be
> Have you seen that happen ever ? AL is Arbitration Lost, we never put
> OMAP in a multi-master environment before.
This is an example from real life:
[    0.271942] omap_i2c omap_i2c.1: bus 1 rev2.4.0 at 400 kHz
[    1.283416] omap_i2c omap_i2c.1: timeout waiting for bus ready
[    1.300109] OMAP_I2C DEBUG: stat=1001
[    1.300140] omap_i2c omap_i2c.1: Arbitration lost
[    1.300140] OMAP_I2C DEBUG: IE=601F
[    1.300140] OMAP_I2C DEBUG: STAT=1000
[    1.300170] OMAP_I2C DEBUG: IV=636F
[    1.300170] OMAP_I2C DEBUG: WE=636F
[    1.300170] OMAP_I2C DEBUG: SYSS=1
[    1.300170] OMAP_I2C DEBUG: BUF=707
[    1.300201] OMAP_I2C DEBUG: CNT=1
[    1.300201] OMAP_I2C DEBUG: DATA=1
[    1.300201] OMAP_I2C DEBUG: SYSC=215
[    1.300201] OMAP_I2C DEBUG: CON=8200
[    1.300231] OMAP_I2C DEBUG: OA=0
[    1.300231] OMAP_I2C DEBUG: SA=49
[    1.300231] OMAP_I2C DEBUG: PSC=9
[    1.300262] OMAP_I2C DEBUG: SCLL=9
[    1.300262] OMAP_I2C DEBUG: SCLH=3
[    1.300262] OMAP_I2C DEBUG: SYSTEST=1E0
[    1.300262] OMAP_I2C DEBUG: BUFSTAT=4000

and my headache now :..(
>
> ARDY | NACK I also find it a bit hard for those two to happen together
> since ARDY will be set when you can change controller's register
> *again*, mening that a transfer has completed.
There are examples:
[    3.544952] omap_i2c 48060000.i2c: IRQ (ISR = 0x0006)

[   25.574523] omap_i2c 48350000.i2c: IRQ (ISR = 0x0014)
[   25.579925] omap_i2c 48350000.i2c: IRQ (ISR = 0x0012)

to see it - enable debug output in omap_i2c_isr_thread:
         dev_dbg(dev->dev, "IRQ (ISR = 0x%04x)\n", stat);

>
> Also, we need to follow what the programming model says. And, I don't
> have docs with me right now, but IIRC it tells us to bail out if any of
> the error conditions are met.
>
yep, but first of all - all IRQs need to be acked before exit.

Sorry, for delayed reply - I've had problems with my e-mail.

- grygorii

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