On 06/19/2014 05:07 PM, Felipe Balbi wrote: > On Wed, Jun 18, 2014 at 11:36:43AM +0200, Daniel Mack wrote: >> On 06/18/2014 11:32 AM, David Laight wrote: >>> From: Of Daniel Mack >>>> Sent: 18 June 2014 10:28 >>>> To: balbi@xxxxxx; george.cherian@xxxxxx; bigeasy@xxxxxxxxxxxxx >>>> Cc: sebastian.reimers@xxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; Daniel Mack >>>> Subject: [PATCH 2/2] usb: musb: cppi41: fire hrtimer according to programmed channel length >>>> >>>> The musb/cppi41 code installs a hrtimer to work around DMA completion >>>> interrupts that have fired too early on AM335x hardware. This timer >>>> is currently programmed to first fire 140 nanoseconds after the DMA >>>> completion callback. According to the commit which introduced it >>>> (a655f481d83, "usb: musb: musb_cppi41: handle pre-mature TX complete >>>> interrupt"), that value is is considered a 'rule of thumb' that worked >>>> well with the test case described in the commit log. >>>> >>>> Test show, however, that for USB audio devices and much smaller packet >>>> sizes, the timer has to fire earlier in order to correctly handle the audio >>>> stream. The original test case had output transfer sizes of 1514 bytes, and >>>> a delay of 140 nanoseconds. For audio devices with 24 bytes channel size, 3 >>>> nanoseconds seem to work well. >>> >>> You can't really mean nanoseconds? >> >> Microseconds of course. Thanks for the heads-up. Fixed locally. > > Are you sending another one or want me to fix the commit log when > applying here ? I was actually waiting for feedback on the patch before resending another version. In particular, I'd like to know whether George's test case still works with this patch applied. If nobody has objections, you fixing the commit log would of course be easiest, yes :) Thanks, Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
