Re: [PATCH 2/4] media: rc: sunxi-cir: add support for the A523

[Justin Suess <utilityemal77@gmail.com>]

On Fri, Jul 03, 2026 at 11:11:59AM +0200, Andre Przywara wrote:
> On Thu,  2 Jul 2026 17:47:48 -0400
> Justin Suess <utilityemal77@gmail.com> wrote:
> 
> Hi Justin,
> 
> many thanks for sending this!
> 
> > The A523 (sun55i) has a newer revision of the CIR receiver IP. Two
> > register fields that do not exist on older SoCs must be programmed
> > for reception to work:
> > 
> >  - CTL bits [7:6] select which pulse polarities are captured into the
> >    RX FIFO. The reset value of 0 captures nothing, so program "both
> >    pulse" mode, which captures regardless of header polarity.
> 
> Are you sure about that? The manual says that *both* the 0b00 (reset
> default) and 0b01 values capture both edges, and actually the H6, A133
> and H616 have the same bits, and it apparently works there.
>
No, actually. I literally just live dumped the registers on the vendor
kernel, (my android tv came pre-rooted for some reason) and interpreted
the purpose from the BSP source.

I am actually unaware there was such a manual. If you could point me to
it that'd be great.
> I don't see those bits documented in the A64 (and earlier), but haven't
> checked yet whether they exist there regardless or have an effect.
> So I think we should force those bits either to 0 or to 1, depending on how
> those bits behave on A64 and before, and how compatible this is with H6,
> A133, H616. I will try to run some experiments on the weekend.
>
Appreciate it!

I'll wait for the results of that experiment, I don't feel confident
enough that I wouldn't break things by even forcing the register to zero
without hardware to test on. So I preserved the existing behavior for the non
X98qpro+ board to be safe.

> >  - SPLCFG (the sample configuration register) bits [1:0] select the
> >    sample clock as a division of the module clock, replacing the
> >    fixed module clock / 64 sample rate of the older IP.
> 
> That's not fully correct: even the A20(!) has these two bits, actually
> there is a third bit, held in bit 24 (because reasons). All those bits
> reset to 0, which is encoded as /64, so this is where the rate comes
> from. And sunxi_ir_probe() sets the IR clock to 8MHz, which should end
> up as 24MHz / 3, on all chips, including the A523.
> 
> So what is going on here? Is the manual wrong, about those bits, or the
> clock sources?
> Can you point to the BSP sources, if you used those?
>

Actually I relied on a script running sunxi-dump on the vendor
kernel and dumping the registers for an initial implementation.

It didn't work, and I was getting stuck. (probably my sampling script
didn't dump the registers fast enough and didn't include all of the ones
needed).

Then I found https://github.com/chainsx/linux-sun55iw3-vendor

And saw this

  #define IR_SAMPLE_DEV		(0x2 << 0)	/* 24MHz/256 =93750Hz (~10.7us)*/

for the clock rate.

And then this one:

  #define IR_BOTH_PULSE		(0x1 << 6)

As and saw it being used as the pulse polarity.

(above are in bsp/drivers/ir-rx/sunxi-ir-rx.c)

And figured to give this one a try because everything I tried before
messing with the existing constants in mainline failed, and this was
the primary construct that didn't match up with mainline. 

Those two things were enough to get it working perfectly on my hardware.

So this is more based on "this is what worked on the hardware" + a
cursory read of the vendor source than based on any hardware technical
document or manual... I should have been more upfront about that.

So please point me to this manual and I can revise and figure out WHY
this works and improve this patch series. 

> >    module clock / 256, which together with the 24 MHz module clock
> 
> Why is the A523 mod clock set to 24 MHz? You seem to do this in the DT,
> overriding the 8MHz default? The driver clearly has a clk_set_rate() call
> with that default 8MHz as an argument, and I don't think we should deviate
> from that, unless there are good reasons. The sample clock should be more of
> a driver/subsystem decision, not a a device one.
> 

See above. This is just what worked on the hardware, and what the vendor
set. And it worked so I sent it. I didn't have access to the manual...

but agreed this needs justification and not just a handwaving "works on
my machine".

> >    used on the A523 gives a 10.7 μs sample period, close to the 8 μs
> >    of the previous 8 MHz / 64 configuration, and keeps the default
> >    125 ms idle timeout representable in the 8-bit idle threshold
> 
> This is some good info that helps people understand the reasoning behind
> those timing values. Please put this in a comment near the top of the file.
> But actually: how does this compute? With an 8us sample clock period, the
> 8-bit ATHR field only covers 2 ms. And I don't see us setting the ATHC bit
> to bump this by 128.
> 
I'll include it and anything else I can glean from your testing, and if
you can point me to the manual.

Thanks for the swift review, sorry should have made more obvious up
front this was a "tweaking until it works" implementation, not a ground
up spec based implementation.

> Cheers,
> Andre
> 
> >    field.
> > 
> > Parameterize the sample divisor in the resolution/timeout
> > calculations, which older SoCs keep at the fixed 64, and add the
> > A523 quirks and compatible.
> > 
> > Signed-off-by: Justin Suess <utilityemal77@gmail.com>
> > ---
> >  drivers/media/rc/sunxi-cir.c | 76 ++++++++++++++++++++++++++++++------
> >  1 file changed, 63 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/media/rc/sunxi-cir.c b/drivers/media/rc/sunxi-cir.c
> > index cb4c56bf0752..82ada9dc0347 100644
> > --- a/drivers/media/rc/sunxi-cir.c
> > +++ b/drivers/media/rc/sunxi-cir.c
> > @@ -31,6 +31,11 @@
> >  /* CIR mode */
> >  #define REG_CTL_MD			(BIT(4) | BIT(5))
> > +/* Pulse mode selector (bits [7:6]) */
> > +#define REG_CTL_PMD(m)			((m) << 6)
> > +/* Capture both pulse polarities */
> > +#define REG_CTL_PMD_BOTH		REG_CTL_PMD(1)
> > +
> >  /* Rx Config */
> >  #define SUNXI_IR_RXCTL_REG    0x10
> >  /* Pulse Polarity Invert flag */
> > @@ -66,6 +71,13 @@
> >  /* IR Sample Config */
> >  #define SUNXI_IR_CIR_REG      0x34
> > +/*
> > + * Sample clock divider select (bits [1:0]), present on newer IP revisions
> > + * (e.g. sun55i). Selects the sample clock as a fraction of the module clock;
> > + * must be programmed for the sampler to run. Older SoCs lack the field and
> > + * use a fixed module-clock/64 sample rate, so they leave it 0.
> > + */
> > +#define REG_CIR_SDIV(val)    ((val) & GENMASK(1, 0))
> >  /* CIR_REG register noise threshold */
> >  #define REG_CIR_NTHR(val)    (((val) << 2) & (GENMASK(7, 2)))
> >  /* CIR_REG register idle threshold */
> > @@ -73,6 +85,8 @@
> >  /* Required frequency for IR0 or IR1 clock in CIR mode (default) */
> >  #define SUNXI_IR_BASE_CLK     8000000
> > +/* Default sample clock divisor: module clock / 64 (legacy fixed rate) */
> > +#define SUNXI_IR_SAMPLE_DIV   64
> >  /* Noise threshold in samples  */
> >  #define SUNXI_IR_RXNOISE      1
> > @@ -81,10 +95,18 @@
> >   *
> >   * @has_reset: SoC needs reset deasserted.
> >   * @fifo_size: size of the fifo.
> > + * @both_pulse: program the CTRL pulse-mode field (newer IP revisions).
> 
> As mentioned above, those bits exist in earlier IP as well. Typically
> non-implemented bits in Allwinner IP as RES0, so I think we can program them
> unconditionally (and should on H6/A133/H616) and don't need a quirks flag.
> 
Yeah, probably just setting them to zero is *fine* for the non-a523
hardware, but I didn't want to send patches for hardware I can't test.

Last thing I want to do is make someones TV remote stop working.

If your experiments reveal forcing zero is OK, than I'll default to
that.

> > + * @sample_div_sel: value for the SPLCFG sample-clock divider field (0 on
> > + *		    legacy SoCs that lack the field).
> 
> Same here: those bits exist back to the A20, even. And their meaning didn't
> change, if I see this correctly. So no quirk needed, instead we should
> program them explicitly to the value we want (probably 0).
> 
Sounds good
> > + * @sample_divisor: module-clock divisor that yields the sample clock; matches
> > + *		    @sample_div_sel on newer IP, or the fixed /64 on legacy SoCs.
> 
> That looks odd: why do we have that value in the first place? Following the
> things I mention above, the divisor shouldn't be different on the A523. And
> also, I think we should just do the math in the driver, and calculate the
> divisor, based on some timing requirement. Which could be something like:
> aim for a clock period of 8us. Though all the parameters seem to be stable:
> the 24 MHz OSC input, the dividers in the mod clock, and the post dividers
> in register 0x34. So there wouldn't be much of a calculation, really. But I
> still think the driver can figure this out itself, and doesn't need explicit
> telling of a divisor.
> 
This is just what worked for me; and what the vendor did. But you're
right, we shouldn't trust it if the quality of the bsp code is anything
to go off of.

> So I think we would need a separate patch to fix up driver operation before
> A523. Then the A523 bits should go on top of this. And maybe make this two
> patches, one for the edge sample bits, one for the clock calculation.
> 
Easy enough. I'll wait on your experiments, please send whatever you
found here while I prepare the seperate patches, and I'll adjust before
resending (no rush on the results, all I'd need is you forcing the
register to zero and verifying it works)

(and please if you could drop me this manual, would have saved me a lot of time!
I couldn't find it anywhere!)

Justin
> Cheers,
> Andre
> 
> >   */
> >  struct sunxi_ir_quirks {
> >  	bool		has_reset;
> >  	int		fifo_size;
> > +	bool		both_pulse;
> > +	u8		sample_div_sel;
> > +	u32		sample_divisor;
> >  };
> >  struct sunxi_ir {
> > @@ -92,6 +114,9 @@ struct sunxi_ir {
> >  	void __iomem    *base;
> >  	int             irq;
> >  	int		fifo_size;
> > +	bool		both_pulse;
> > +	u8		sample_div_sel;
> > +	u32		sample_divisor;
> >  	struct clk      *clk;
> >  	struct clk      *apb_clk;
> >  	struct reset_control *rst;
> > @@ -140,17 +165,19 @@ static irqreturn_t sunxi_ir_irq(int irqno, void *dev_id)
> >  }
> >  /* Convert idle threshold to usec */
> > -static unsigned int sunxi_ithr_to_usec(unsigned int base_clk, unsigned int ithr)
> > +static unsigned int sunxi_ithr_to_usec(unsigned int base_clk, unsigned int div,
> > +				       unsigned int ithr)
> >  {
> >  	return DIV_ROUND_CLOSEST(USEC_PER_SEC * (ithr + 1),
> > -				 base_clk / (128 * 64));
> > +				 base_clk / (128 * div));
> >  }
> >  /* Convert usec to idle threshold */
> > -static unsigned int sunxi_usec_to_ithr(unsigned int base_clk, unsigned int usec)
> > +static unsigned int sunxi_usec_to_ithr(unsigned int base_clk, unsigned int div,
> > +				       unsigned int usec)
> >  {
> >  	/* make sure we don't end up with a timeout less than requested */
> > -	return DIV_ROUND_UP((base_clk / (128 * 64)) * usec,  USEC_PER_SEC) - 1;
> > +	return DIV_ROUND_UP((base_clk / (128 * div)) * usec,  USEC_PER_SEC) - 1;
> >  }
> >  static int sunxi_ir_set_timeout(struct rc_dev *rc_dev, unsigned int timeout)
> > @@ -158,15 +185,17 @@ static int sunxi_ir_set_timeout(struct rc_dev *rc_dev, unsigned int timeout)
> >  	struct sunxi_ir *ir = rc_dev->priv;
> >  	unsigned int base_clk = clk_get_rate(ir->clk);
> > -	unsigned int ithr = sunxi_usec_to_ithr(base_clk, timeout);
> > +	unsigned int ithr = sunxi_usec_to_ithr(base_clk, ir->sample_divisor,
> > +					       timeout);
> >  	dev_dbg(rc_dev->dev.parent, "setting idle threshold to %u\n", ithr);
> > -	/* Set noise threshold and idle threshold */
> > -	writel(REG_CIR_NTHR(SUNXI_IR_RXNOISE) | REG_CIR_ITHR(ithr),
> > +	/* Set sample clock divider, noise threshold and idle threshold */
> > +	writel(REG_CIR_SDIV(ir->sample_div_sel) |
> > +	       REG_CIR_NTHR(SUNXI_IR_RXNOISE) | REG_CIR_ITHR(ithr),
> >  	       ir->base + SUNXI_IR_CIR_REG);
> > -	rc_dev->timeout = sunxi_ithr_to_usec(base_clk, ithr);
> > +	rc_dev->timeout = sunxi_ithr_to_usec(base_clk, ir->sample_divisor, ithr);
> >  	return 0;
> >  }
> > @@ -193,8 +222,14 @@ static int sunxi_ir_hw_init(struct device *dev)
> >  		goto exit_disable_apb_clk;
> >  	}
> > -	/* Enable CIR Mode */
> > -	writel(REG_CTL_MD, ir->base + SUNXI_IR_CTL_REG);
> > +	/*
> > +	 * Enable CIR Mode. On newer IP revisions the pulse-mode field must
> > +	 * also be set, otherwise no pulses are captured into the RX FIFO.
> > +	 */
> > +	tmp = REG_CTL_MD;
> > +	if (ir->both_pulse)
> > +		tmp |= REG_CTL_PMD_BOTH;
> > +	writel(tmp, ir->base + SUNXI_IR_CTL_REG);
> >  	/* Set noise threshold and idle threshold */
> >  	sunxi_ir_set_timeout(ir->rc, ir->rc->timeout);
> > @@ -271,6 +306,9 @@ static int sunxi_ir_probe(struct platform_device *pdev)
> >  	}
> >  	ir->fifo_size = quirks->fifo_size;
> > +	ir->both_pulse = quirks->both_pulse;
> > +	ir->sample_div_sel = quirks->sample_div_sel;
> > +	ir->sample_divisor = quirks->sample_divisor ?: SUNXI_IR_SAMPLE_DIV;
> >  	/* Clock */
> >  	ir->apb_clk = devm_clk_get(dev, "apb");
> > @@ -325,10 +363,10 @@ static int sunxi_ir_probe(struct platform_device *pdev)
> >  	ir->rc->dev.parent = dev;
> >  	ir->rc->allowed_protocols = RC_PROTO_BIT_ALL_IR_DECODER;
> >  	/* Frequency after IR internal divider with sample period in us */
> > -	ir->rc->rx_resolution = (USEC_PER_SEC / (b_clk_freq / 64));
> > +	ir->rc->rx_resolution = (USEC_PER_SEC / (b_clk_freq / ir->sample_divisor));
> >  	ir->rc->timeout = IR_DEFAULT_TIMEOUT;
> > -	ir->rc->min_timeout = sunxi_ithr_to_usec(b_clk_freq, 0);
> > -	ir->rc->max_timeout = sunxi_ithr_to_usec(b_clk_freq, 255);
> > +	ir->rc->min_timeout = sunxi_ithr_to_usec(b_clk_freq, ir->sample_divisor, 0);
> > +	ir->rc->max_timeout = sunxi_ithr_to_usec(b_clk_freq, ir->sample_divisor, 255);
> >  	ir->rc->s_timeout = sunxi_ir_set_timeout;
> >  	ir->rc->driver_name = SUNXI_IR_DEV;
> > @@ -395,6 +433,14 @@ static const struct sunxi_ir_quirks sun6i_a31_ir_quirks = {
> >  	.fifo_size = 64,
> >  };
> > +static const struct sunxi_ir_quirks sun55i_a523_ir_quirks = {
> > +	.has_reset = true,
> > +	.fifo_size = 64,
> > +	.both_pulse = true,
> > +	.sample_div_sel = 2,	/* sample clock = module clock / 256 */
> > +	.sample_divisor = 256,
> > +};
> > +
> >  static const struct of_device_id sunxi_ir_match[] = {
> >  	{
> >  		.compatible = "allwinner,sun4i-a10-ir",
> > @@ -408,6 +454,10 @@ static const struct of_device_id sunxi_ir_match[] = {
> >  		.compatible = "allwinner,sun6i-a31-ir",
> >  		.data = &sun6i_a31_ir_quirks,
> >  	},
> > +	{
> > +		.compatible = "allwinner,sun55i-a523-ir",
> > +		.data = &sun55i_a523_ir_quirks,
> > +	},
> >  	{}
> >  };
> >  MODULE_DEVICE_TABLE(of, sunxi_ir_match);
>