Re: [PATCH v2] usb: dwc2: hcd_queue: Fix use of floating point literal

[Minas Harutyunyan]

On 11/5/2021 7:15 PM, John Keeping wrote:
> On Fri, Nov 05, 2021 at 07:58:03AM -0700, Nathan Chancellor wrote:
>> A new commit in LLVM causes an error on the use of 'long double' when
>> '-mno-x87' is used, which the kernel does through an alias,
>> '-mno-80387' (see the LLVM commit below for more details around why it
>> does this).
>>
>>   drivers/usb/dwc2/hcd_queue.c:1744:25: error: expression requires  'long double' type support, but target 'x86_64-unknown-linux-gnu' does not support it
>>                           delay = ktime_set(0, DWC2_RETRY_WAIT_DELAY);
>>                                               ^
>>   drivers/usb/dwc2/hcd_queue.c:62:34: note: expanded from macro 'DWC2_RETRY_WAIT_DELAY'
>>   #define DWC2_RETRY_WAIT_DELAY (1 * 1E6L)
>>                                   ^
>>   1 error generated.
>>
>> This happens due to the use of a 'long double' literal. The 'E6' part of
>> '1E6L' causes the literal to be a 'double' then the 'L' suffix promotes
>> it to 'long double'.
>>
>> There is no visible reason for a floating point value in this driver, as
>> the value is only used as a parameter to a function that expects an
>> integer type. Use NSEC_PER_MSEC, which is the same integer value as
>> '1E6L', to avoid changing functionality but fix the error.
>>
>> Fixes: 6ed30a7d8ec2 ("usb: dwc2: host: use hrtimer for NAK retries")
>> Link: https://urldefense.com/v3/__https://github.com/ClangBuiltLinux/linux/issues/1497__;!!A4F2R9G_pg!KuhWEjrjOQ8CCBd81IpZ5GxP7Sksp_VESbrQ2QTDnLQBOWN7E1YrD0iJCn9fUAU$
>> Link: https://urldefense.com/v3/__https://github.com/llvm/llvm-project/commit/a8083d42b1c346e21623a1d36d1f0cadd7801d83__;!!A4F2R9G_pg!KuhWEjrjOQ8CCBd81IpZ5GxP7Sksp_VESbrQ2QTDnLQBOWN7E1YrD0iJyK66ZHc$
>> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
>> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> 
> Reviewed-by: John Keeping <john@xxxxxxxxxxxx>

Acked-by: Minas Harutyunyan <Minas.Harutyunyan@xxxxxxxxxxxx>

> 
>> ---
>>
>> v1 -> v2: https://urldefense.com/v3/__https://lore.kernel.org/r/20211104215923.719785-1-nathan@xxxxxxxxxx/__;!!A4F2R9G_pg!KuhWEjrjOQ8CCBd81IpZ5GxP7Sksp_VESbrQ2QTDnLQBOWN7E1YrD0iJwwZgtI8$
>>
>> * Use NSEC_PER_MSEC instead of USEC_PER_SEC, as the units of the second
>>    parameter of ktime_set is nanoseconds. Thanks to John Keeping for
>>    pointing this out.
>>
>> * Pick up Nick's review tag.
>>
>>   drivers/usb/dwc2/hcd_queue.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc2/hcd_queue.c b/drivers/usb/dwc2/hcd_queue.c
>> index 89a788326c56..24beff610cf2 100644
>> --- a/drivers/usb/dwc2/hcd_queue.c
>> +++ b/drivers/usb/dwc2/hcd_queue.c
>> @@ -59,7 +59,7 @@
>>   #define DWC2_UNRESERVE_DELAY (msecs_to_jiffies(5))
>>   
>>   /* If we get a NAK, wait this long before retrying */
>> -#define DWC2_RETRY_WAIT_DELAY (1 * 1E6L)
>> +#define DWC2_RETRY_WAIT_DELAY (1 * NSEC_PER_MSEC)
>>   
>>   /**
>>    * dwc2_periodic_channel_available() - Checks that a channel is available for a
>>
>> base-commit: d4439a1189f93d0ac1eaf0197db8e6b3e197d5c7
>> -- 
>> 2.34.0.rc0
>>