Re: [RFC 1/5] [media] rc: update sunxi-ir driver to get base frequency from devicetree

[Philipp Rossak <embed3d@xxxxxxxxx>]

Hey Mauro,

Thanks for your fast feedback!

I will rework the driver like you suggested it.

Does somebody have any concerns about the Devicetree property 
(base-clk-frequency = < frequency >;)?


Regards,
Philipp

On 16.12.2017 10:18, Mauro Carvalho Chehab wrote:
> Em Sat, 16 Dec 2017 03:49:10 +0100
> Philipp Rossak <embed3d@xxxxxxxxx> escreveu:
>
> Hi Phillip,
>
> This is not a full review of this patchset. I just want to point you
> that you should keep supporting existing DT files.
>
> > This patch updates the sunxi-ir driver to set the ir base clock from
> > devicetree.
> >
> > This is neccessary since there are different ir recievers on the
> > market, that operate with different frequencys. So this value needs to
> > be set depending on the attached receiver.
>
> Please don't break backward compatibility with old DT files. In this
> specific case, it seems simple enough to be backward-compatible.
>
> > Signed-off-by: Philipp Rossak <embed3d@xxxxxxxxx>
> > ---
> >   drivers/media/rc/sunxi-cir.c | 20 +++++++++++---------
> >   1 file changed, 11 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/media/rc/sunxi-cir.c b/drivers/media/rc/sunxi-cir.c
> > index 97f367b446c4..55b53d6463e9 100644
> > --- a/drivers/media/rc/sunxi-cir.c
> > +++ b/drivers/media/rc/sunxi-cir.c
> > @@ -72,12 +72,6 @@
> >   /* CIR_REG register idle threshold */
> >   #define REG_CIR_ITHR(val)    (((val) << 8) & (GENMASK(15, 8)))
> >   
> > -/* Required frequency for IR0 or IR1 clock in CIR mode */
> > -#define SUNXI_IR_BASE_CLK     8000000
> > -/* Frequency after IR internal divider  */
> > -#define SUNXI_IR_CLK          (SUNXI_IR_BASE_CLK / 64)
>
> Keep those to definitions...
>
> > -/* Sample period in ns */
> > -#define SUNXI_IR_SAMPLE       (1000000000ul / SUNXI_IR_CLK)
> >   /* Noise threshold in samples  */
> >   #define SUNXI_IR_RXNOISE      1
> >   /* Idle Threshold in samples */
> > @@ -122,7 +116,7 @@ static irqreturn_t sunxi_ir_irq(int irqno, void *dev_id)
> >   			/* for each bit in fifo */
> >   			dt = readb(ir->base + SUNXI_IR_RXFIFO_REG);
> >   			rawir.pulse = (dt & 0x80) != 0;
> > -			rawir.duration = ((dt & 0x7f) + 1) * SUNXI_IR_SAMPLE;
> > +			rawir.duration = ((dt & 0x7f) + 1) * ir->rc->rx_resolution;
> >   			ir_raw_event_store_with_filter(ir->rc, &rawir);
> >   		}
> >   	}
> > @@ -148,6 +142,7 @@ static int sunxi_ir_probe(struct platform_device *pdev)
> >   	struct device_node *dn = dev->of_node;
> >   	struct resource *res;
> >   	struct sunxi_ir *ir;
> > +	u32 b_clk_freq;
> >   
> >   	ir = devm_kzalloc(dev, sizeof(struct sunxi_ir), GFP_KERNEL);
> >   	if (!ir)
> > @@ -172,6 +167,12 @@ static int sunxi_ir_probe(struct platform_device *pdev)
> >   		return PTR_ERR(ir->clk);
> >   	}
> >   
> > +	/* Required frequency for IR0 or IR1 clock in CIR mode */
> > +	if (of_property_read_u32(dn, "base-clk-frequency", &b_clk_freq)) {
> > +		dev_err(dev, "failed to get ir base clock frequency.\n");
> > +		return -ENODATA;
> > +	}
> > +
>
> And here, instead of returning an error, if the property can't be read,
> it means it is an older DT file. Just default to SUNXI_IR_BASE_CLK.
> This will make it backward-compatible with old DT files that don't have
> such property.
>
> Regards,
> Mauro
>
>
> >   	/* Reset (optional) */
> >   	ir->rst = devm_reset_control_get_optional_exclusive(dev, NULL);
> >   	if (IS_ERR(ir->rst))
> > @@ -180,7 +181,7 @@ static int sunxi_ir_probe(struct platform_device *pdev)
> >   	if (ret)
> >   		return ret;
> >   
> > -	ret = clk_set_rate(ir->clk, SUNXI_IR_BASE_CLK);
> > +	ret = clk_set_rate(ir->clk, b_clk_freq);
> >   	if (ret) {
> >   		dev_err(dev, "set ir base clock failed!\n");
> >   		goto exit_reset_assert;
> > @@ -225,7 +226,8 @@ static int sunxi_ir_probe(struct platform_device *pdev)
> >   	ir->rc->map_name = ir->map_name ?: RC_MAP_EMPTY;
> >   	ir->rc->dev.parent = dev;
> >   	ir->rc->allowed_protocols = RC_PROTO_BIT_ALL_IR_DECODER;
> > -	ir->rc->rx_resolution = SUNXI_IR_SAMPLE;
> > +	/* Frequency after IR internal divider with sample period in ns */
> > +	ir->rc->rx_resolution = (1000000000ul / (b_clk_freq / 64));
> >   	ir->rc->timeout = MS_TO_NS(SUNXI_IR_TIMEOUT);
> >   	ir->rc->driver_name = SUNXI_IR_DEV;
> >   
>
> Thanks,
> Mauro