[PATCH] usb: dwc3: core: fix clk_get_rate returning negative value

[Eugen Hristev]

On 6/15/23 23:59, Marek Vasut wrote:
> On 6/15/23 16:59, Eugen Hristev wrote:
>> Unlike it's Linux counterpart, clk_get_rate can return a negative 
>> value, -ve.
>> The driver does not take that into account, stores the rate into
>> an unsigned long, and if clk_get_rate fails, it will take into 
>> consideration
>> the actual value and wrongly program the hardware.
>> E.g. on error -2 (no such entry), the rate will be 18446744073709551614
>> and this will be subsequently used by the driver to program the DWC3
>> To fix this, exit the function if the value is negative.
>>
>> Fixes: 6bae0eb5b8bd ("usb: dwc3: Calculate REFCLKPER based on 
>> reference clock")
>> Signed-off-by: Eugen Hristev <eugen.hristev at collabora.com>
>> ---
>>   drivers/usb/dwc3/core.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 49f6a1900b01..5a8c29424578 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -138,7 +138,7 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc)
>>       if (dwc->ref_clk) {
>>           rate = clk_get_rate(dwc->ref_clk);
> 
> This ^ assigns to unsigned long .

That's right, because clk_get_rate returns an unsigned long
> 
> Please just change the data type of the $rate to 'long' (drop the 
> unsigned).

clk_get_rate returns unsigned long, so it's not normal to assign it to a 
signed long.

It is not normal that clk_get_rate returns negative values in an 
unsigned, but oh well, that's how the clock API is in U-boot

> 
>> -        if (!rate)
>> +        if (!rate || (long)rate < 0)
> 
> if (rate <= 0) will work too ^