Re: [PATCH 3/5] rc: img-ir: biphase enabled with workaround

[James Hogan <james.hogan@imgtec.com>]

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On 04/12/14 15:38, Sifan Naeem wrote:
> Biphase decoding in the current img-ir has got a quirk, where multiple
> Interrupts are generated when an incomplete IR code is received by the
> decoder.
> 
> Patch adds a work around for the quirk and enables biphase decoding.
> 
> Signed-off-by: Sifan Naeem <sifan.naeem@imgtec.com>
> ---
>  drivers/media/rc/img-ir/img-ir-hw.c |   56 +++++++++++++++++++++++++++++++++--
>  drivers/media/rc/img-ir/img-ir-hw.h |    2 ++
>  2 files changed, 55 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/rc/img-ir/img-ir-hw.c b/drivers/media/rc/img-ir/img-ir-hw.c
> index 4a1407b..a977467 100644
> --- a/drivers/media/rc/img-ir/img-ir-hw.c
> +++ b/drivers/media/rc/img-ir/img-ir-hw.c
> @@ -52,6 +52,11 @@ static struct img_ir_decoder *img_ir_decoders[] = {
>  
>  #define IMG_IR_QUIRK_CODE_BROKEN	0x1	/* Decode is broken */
>  #define IMG_IR_QUIRK_CODE_LEN_INCR	0x2	/* Bit length needs increment */
> +/*
> + * The decoder generates rapid interrupts without actually having
> + * received any new data after an incomplete IR code is decoded.
> + */
> +#define IMG_IR_QUIRK_CODE_IRQ		0x4
>  
>  /* functions for preprocessing timings, ensuring max is set */
>  
> @@ -547,6 +552,7 @@ static void img_ir_set_decoder(struct img_ir_priv *priv,
>  
>  	/* stop the end timer and switch back to normal mode */
>  	del_timer_sync(&hw->end_timer);
> +	del_timer_sync(&hw->suspend_timer);

FYI, this'll need rebasing due to conflicting with "img-ir/hw: Fix
potential deadlock stopping timer". The new del_timer_sync will need to
be when spin lock isn't held, i.e. still next to the other one, and
don't forget to ensure that suspend_timer doesn't get started if
hw->stopping.

>  	hw->mode = IMG_IR_M_NORMAL;
>  
>  	/* clear the wakeup scancode filter */
> @@ -843,6 +849,26 @@ static void img_ir_end_timer(unsigned long arg)
>  	spin_unlock_irq(&priv->lock);
>  }
>  
> +/*
> + * Timer function to re-enable the current protocol after it had been
> + * cleared when invalid interrupts were generated due to a quirk in the
> + * img-ir decoder.
> + */
> +static void img_ir_suspend_timer(unsigned long arg)
> +{
> +	struct img_ir_priv *priv = (struct img_ir_priv *)arg;
> +

You should take the spin lock for most of this function now that
"img-ir/hw: Fix potential deadlock stopping timer" is applied and it is
safe to do so.

> +	img_ir_write(priv, IMG_IR_IRQ_CLEAR,
> +			IMG_IR_IRQ_ALL & ~IMG_IR_IRQ_EDGE);
> +
> +	/* Don't set IRQ if it has changed in a different context. */

Wouldn't hurt to clarify this while you're at it (it confused me for a
moment thinking it was concerned about the enabled raw event IRQs
(IMG_IR_IRQ_EDGE) changing).

Maybe "Don't overwrite enabled valid/match IRQs if they have already
been changed by e.g. a filter change".

Should you even be clearing IRQs in that case? Maybe safer to just treat
that case as a "return immediately without touching anything" sort of
situation.

> +	if ((priv->hw.suspend_irqen & IMG_IR_IRQ_EDGE) ==
> +				img_ir_read(priv, IMG_IR_IRQ_ENABLE))
> +		img_ir_write(priv, IMG_IR_IRQ_ENABLE, priv->hw.suspend_irqen);
> +	/* enable */
> +	img_ir_write(priv, IMG_IR_CONTROL, priv->hw.reg_timings.ctrl);
> +}
> +
>  #ifdef CONFIG_COMMON_CLK
>  static void img_ir_change_frequency(struct img_ir_priv *priv,
>  				    struct clk_notifier_data *change)
> @@ -908,15 +934,37 @@ void img_ir_isr_hw(struct img_ir_priv *priv, u32 irq_status)
>  	if (!hw->decoder)
>  		return;
>  
> +	ct = hw->decoder->control.code_type;
> +
>  	ir_status = img_ir_read(priv, IMG_IR_STATUS);
> -	if (!(ir_status & (IMG_IR_RXDVAL | IMG_IR_RXDVALD2)))
> +	if (!(ir_status & (IMG_IR_RXDVAL | IMG_IR_RXDVALD2))) {
> +		if (!(priv->hw.ct_quirks[ct] & IMG_IR_QUIRK_CODE_IRQ))

(I suggest adding "|| hw->stopping" to this case)

> +			return;
> +		/*
> +		 * The below functionality is added as a work around to stop
> +		 * multiple Interrupts generated when an incomplete IR code is
> +		 * received by the decoder.
> +		 * The decoder generates rapid interrupts without actually
> +		 * having received any new data. After a single interrupt it's
> +		 * expected to clear up, but instead multiple interrupts are
> +		 * rapidly generated. only way to get out of this loop is to
> +		 * reset the control register after a short delay.
> +		 */
> +		img_ir_write(priv, IMG_IR_CONTROL, 0);
> +		hw->suspend_irqen = img_ir_read(priv, IMG_IR_IRQ_ENABLE);

You're reusing hw->suspend_irqen. What if you get this workaround being
activated between img_ir_enable_wake() and img_ir_disable_wake()? I
suggest just using a new img_ir_priv_hw member.

The rest looks reasonable to me, even if unfortunate that it is
necessary in the first place.

Thanks for the hard work!

Cheers
James

> +		img_ir_write(priv, IMG_IR_IRQ_ENABLE,
> +			     hw->suspend_irqen & IMG_IR_IRQ_EDGE);
> +
> +		/* Timer activated to re-enable the protocol. */
> +		mod_timer(&hw->suspend_timer,
> +			  jiffies + msecs_to_jiffies(5));
>  		return;
> +	}
>  	ir_status &= ~(IMG_IR_RXDVAL | IMG_IR_RXDVALD2);
>  	img_ir_write(priv, IMG_IR_STATUS, ir_status);
>  
>  	len = (ir_status & IMG_IR_RXDLEN) >> IMG_IR_RXDLEN_SHIFT;
>  	/* some versions report wrong length for certain code types */
> -	ct = hw->decoder->control.code_type;
>  	if (hw->ct_quirks[ct] & IMG_IR_QUIRK_CODE_LEN_INCR)
>  		++len;
>  
> @@ -958,7 +1006,7 @@ static void img_ir_probe_hw_caps(struct img_ir_priv *priv)
>  	hw->ct_quirks[IMG_IR_CODETYPE_PULSELEN]
>  		|= IMG_IR_QUIRK_CODE_LEN_INCR;
>  	hw->ct_quirks[IMG_IR_CODETYPE_BIPHASE]
> -		|= IMG_IR_QUIRK_CODE_BROKEN;
> +		|= IMG_IR_QUIRK_CODE_IRQ;
>  	hw->ct_quirks[IMG_IR_CODETYPE_2BITPULSEPOS]
>  		|= IMG_IR_QUIRK_CODE_BROKEN;
>  }
> @@ -977,6 +1025,8 @@ int img_ir_probe_hw(struct img_ir_priv *priv)
>  
>  	/* Set up the end timer */
>  	setup_timer(&hw->end_timer, img_ir_end_timer, (unsigned long)priv);
> +	setup_timer(&hw->suspend_timer, img_ir_suspend_timer,
> +				(unsigned long)priv);
>  
>  	/* Register a clock notifier */
>  	if (!IS_ERR(priv->clk)) {
> diff --git a/drivers/media/rc/img-ir/img-ir-hw.h b/drivers/media/rc/img-ir/img-ir-hw.h
> index 5e59e8e..8578aa7 100644
> --- a/drivers/media/rc/img-ir/img-ir-hw.h
> +++ b/drivers/media/rc/img-ir/img-ir-hw.h
> @@ -221,6 +221,7 @@ enum img_ir_mode {
>   * @rdev:		Remote control device
>   * @clk_nb:		Notifier block for clock notify events.
>   * @end_timer:		Timer until repeat timeout.
> + * @suspend_timer:	Timer to re-enable protocol.
>   * @decoder:		Current decoder settings.
>   * @enabled_protocols:	Currently enabled protocols.
>   * @clk_hz:		Current core clock rate in Hz.
> @@ -235,6 +236,7 @@ struct img_ir_priv_hw {
>  	struct rc_dev			*rdev;
>  	struct notifier_block		clk_nb;
>  	struct timer_list		end_timer;
> +	struct timer_list		suspend_timer;
>  	const struct img_ir_decoder	*decoder;
>  	u64				enabled_protocols;
>  	unsigned long			clk_hz;
> 


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