[U-Boot] [PATCH v2 09/11] drivers: serial_sifive: Skip baudrate config if no input clock

[Atish Patra]

On 1/20/19 12:22 PM, Auer, Lukas wrote:
> Hi Anup,
> 
> On Fri, 2019-01-18 at 11:19 +0000, Anup Patel wrote:
>> From: Atish Patra <atish.patra at wdc.com>
>>
>> It is possible that input clock is not available because clk
>> device was not available and 'clock-frequency' DT property is
>> also not available.
> 
> Why would the clock device not be available?
> I suspect the problem is that the clock driver is not probed pre-
> relocation. Adding DM_FLAG_PRE_RELOC to the driver flags would fix
> this.
> 

The problem is serial driver gets probed first before clock driver even 
if we add DM_FLAG_PRE_RELOC.

>>
>> In this case, instead of failing we should just skip baudrate
>> config by returning zero.
> 
> Won't this cause issues if an incorrect baudrate is set?
> 
It might be possible that baudrate is configured by earlier boot stage.
Thus, any early information can be displayed in console by the serial 
driver even if it is not configured correctly by u-boot.


Regards,
Atish
> Thanks,
> Lukas
> 
>>
>> Signed-off-by: Atish Patra <atish.patra at wdc.com>
>> Signed-off-by: Anup Patel <anup.patel at wdc.com>
>> Reviewed-by: Alexander Graf <agraf at suse.de>
>> ---
>>   drivers/serial/serial_sifive.c | 32 ++++++++++++++++----------------
>>   1 file changed, 16 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/serial/serial_sifive.c
>> b/drivers/serial/serial_sifive.c
>> index ea4d35d48c..537bc7a975 100644
>> --- a/drivers/serial/serial_sifive.c
>> +++ b/drivers/serial/serial_sifive.c
>> @@ -99,27 +99,27 @@ static int _sifive_serial_getc(struct uart_sifive
>> *regs)
>>   
>>   static int sifive_serial_setbrg(struct udevice *dev, int baudrate)
>>   {
>> -	int err;
>> +	int ret;
>>   	struct clk clk;
>>   	struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
>> +	u32 clock = 0;
>>   
>> -	err = clk_get_by_index(dev, 0, &clk);
>> -	if (!err) {
>> -		err = clk_get_rate(&clk);
>> -		if (!IS_ERR_VALUE(err))
>> -			platdata->clock = err;
>> -	} else if (err != -ENOENT && err != -ENODEV && err != -ENOSYS)
>> {
>> +	ret = clk_get_by_index(dev, 0, &clk);
>> +	if (IS_ERR_VALUE(ret)) {
>>   		debug("SiFive UART failed to get clock\n");
>> -		return err;
>> -	}
>> -
>> -	if (!platdata->clock)
>> -		platdata->clock = dev_read_u32_default(dev, "clock-
>> frequency", 0);
>> -	if (!platdata->clock) {
>> -		debug("SiFive UART clock not defined\n");
>> -		return -EINVAL;
>> +		ret = dev_read_u32(dev, "clock-frequency", &clock);
>> +		if (IS_ERR_VALUE(ret)) {
>> +			debug("SiFive UART clock not defined\n");
>> +			return 0;
>> +		}
>> +	} else {
>> +		clock = clk_get_rate(&clk);
>> +		if (IS_ERR_VALUE(clock)) {
>> +			debug("SiFive UART clock get rate failed\n");
>> +			return 0;
>> +		}
>>   	}
>> -
>> +	platdata->clock = clock;
>>   	_sifive_serial_setbrg(platdata->regs, platdata->clock,
>> baudrate);
>>   
>>   	return 0;
>