Subject: Re: [RFC 1/5] [media] rc: update sunxi-ir driver to get base
 frequency from devicetree
To: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: robh+dt@kernel.org, mark.rutland@arm.com,
        maxime.ripard@free-electrons.com, wens@csie.org, linux@armlinux.org.uk,
        sean@mess.org, p.zabel@pengutronix.de, andi.shyti@samsung.com,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-sunxi@googlegroups.com
References: <20171216024914.7550-1-embed3d@gmail.com>
 <20171216024914.7550-2-embed3d@gmail.com>
 <20171216071855.0ef43f7b@recife.lan>
From: Philipp Rossak <embed3d@gmail.com>
Message-ID: <342789cb-9b49-f1d2-e5f1-2d7e17f774b0@gmail.com>
Date: Sat, 16 Dec 2017 18:30:41 +0100
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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@gmail.com> 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@gmail.com>
>> ---
>>   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
>