-----Original Message----- From: Liam Girdwood [mailto:liam.r.girdwood@linux.intel.com] Sent: Tuesday, December 19, 2017 10:22 PM To: Jie, Yang yang.jie@intel.com; Pierre-Louis Bossart <pierre- louis.bossart@linux.intel.com>; Keyon Jie yang.jie@linux.intel.com; sound- open-firmware@alsa-project.org Subject: Re: [Sound-open-firmware] [PATCH v2 2/3] dai: set dai dma burst_elems according to slot number
On Tue, 2017-12-19 at 14:11 +0000, Jie, Yang wrote:
We should set burst_elems for dma peripheral dev copy, for dai/ssp, it should be set to valid slot number, otherwise, the dma may copy in wrong burst size and data will run with wrong speed.
I don't think the commit message reflects the code, it's really the total number of active slots and not the slot number(s) that we care about,
right?
This is a good topic. At the moment, we are using topology file to configure dai, e.g. DAI_TDM(2, 20, 3, 3), which set num_slots(corresponding to
'slot number(s)'
you mentioned?) to 2 and tx slot mask to 0x3(slot0and slot1 enabled, corresponding to 'the total number' in your context?), so they are same for us
actually at this case.
But imagine that if we set tx slot mask to, e.g. 0x1, should we set burst_elems to 1 or 2? I tend to set 1 at this case, but not 100% sure about it yet, Maybe we need experiment and fix bugs if exist.
So back to your question, I think the answer is yes, using active slots number may be more accurate, though we need experiment on that later.
Keyon, can you submit a patch that make this obvious by means of a code comment or variable name change.
Sure thing. How about changing burst_elems to data_item_num, or valid_item_num?
Thanks, ~Keyon
Thanks
Liam