[rtc-linux] Re: [PATCH 1/5] rtc: m48t86: verify that the RTC is actually present

[Alexander Clouter <alex@digriz.org.uk>]

Thanks, not tested though, as I am lacking in time at the moment.  I 
probably am the only ts7800 user in the world using a mainline kernel 
too...so will only be punishing myself :-)

Acked-By: Alexander Clouter <alex+kernel@digriz.org.uk>


On 21 February 2017 4:37:35 p.m. Alexandre Belloni 
<alexandre.belloni@free-electrons.com> wrote:

> Hi,
>
> On 15/02/2017 at 09:35:23 -0700, H Hartley Sweeten wrote:
>> The RTC is an optional feature at purchase time on some Technologic
>> Systems boards. Verify that it actually exists by checking if the
>> last two bytes of the NVRAM can be changed.
>>
>> Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
>> Cc: Alessandro Zummo <a.zummo@towertech.it>
>> Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>
>> Cc: Alexander Clouter <alex@digriz.org.uk>
>> ---
>>  drivers/rtc/rtc-m48t86.c | 36 ++++++++++++++++++++++++++++++++++++
>>  1 file changed, 36 insertions(+)
>>
>
> I've applied that one. Alex, if you are fine with the mach-orion5x
> changes, I can take them for 4.11. Else, this will wait for 4.12.
>
>> diff --git a/drivers/rtc/rtc-m48t86.c b/drivers/rtc/rtc-m48t86.c
>> index 4dc4af4..41ac5d6 100644
>> --- a/drivers/rtc/rtc-m48t86.c
>> +++ b/drivers/rtc/rtc-m48t86.c
>> @@ -201,6 +201,37 @@ static ssize_t m48t86_nvram_write(struct file *filp, 
>> struct kobject *kobj,
>>  static BIN_ATTR(nvram, 0644, m48t86_nvram_read, m48t86_nvram_write,
>>  		M48T86_NVRAM_LEN);
>>
>> +/*
>> + * The RTC is an optional feature at purchase time on some Technologic Systems
>> + * boards. Verify that it actually exists by checking if the last two bytes
>> + * of the NVRAM can be changed.
>> + *
>> + * This is based on the method used in their rtc7800.c example.
>> + */
>> +static bool m48t86_verify_chip(struct platform_device *pdev)
>> +{
>> +	unsigned int offset0 = M48T86_NVRAM_LEN - 2;
>> +	unsigned int offset1 = M48T86_NVRAM_LEN - 1;
>> +	unsigned char tmp0, tmp1;
>> +
>> +	tmp0 = m48t86_readb(&pdev->dev, offset0);
>> +	tmp1 = m48t86_readb(&pdev->dev, offset1);
>> +
>> +	m48t86_writeb(&pdev->dev, 0x00, offset0);
>> +	m48t86_writeb(&pdev->dev, 0x55, offset1);
>> +	if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
>> +		m48t86_writeb(&pdev->dev, 0xaa, offset1);
>> +		if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
>> +		    m48t86_readb(&pdev->dev, offset0) == 0x00) {
>> +			m48t86_writeb(&pdev->dev, tmp0, offset0);
>> +			m48t86_writeb(&pdev->dev, tmp1, offset1);
>> +
>> +			return true;
>> +		}
>> +	}
>> +	return false;
>> +}
>> +
>>  static int m48t86_rtc_probe(struct platform_device *pdev)
>>  {
>>  	struct m48t86_rtc_info *info;
>> @@ -231,6 +262,11 @@ static int m48t86_rtc_probe(struct platform_device *pdev)
>>
>>  	dev_set_drvdata(&pdev->dev, info);
>>
>> +	if (!m48t86_verify_chip(pdev)) {
>> +		dev_info(&pdev->dev, "RTC not present\n");
>> +		return -ENODEV;
>> +	}
>> +
>>  	info->rtc = devm_rtc_device_register(&pdev->dev, "m48t86",
>>  					     &m48t86_rtc_ops, THIS_MODULE);
>>  	if (IS_ERR(info->rtc))
>> --
>> 2.10.0
>>
>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com


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