> -----Original Message----- > From: Sia, Jee Heng <jee.heng.sia@xxxxxxxxx> > Sent: Tuesday, 24 November, 2020 11:51 AM > To: Shevchenko, Andriy <andriy.shevchenko@xxxxxxxxx> > Cc: Sit, Michael Wei Hong <michael.wei.hong.sit@xxxxxxxxx>; > alsa-devel@xxxxxxxxxxxxxxxx; tiwai@xxxxxxxx; > broonie@xxxxxxxxxx; pierre-louis.bossart@xxxxxxxxxxxxxxx; > Rojewski, Cezary <cezary.rojewski@xxxxxxxxx>; > liam.r.girdwood@xxxxxxxxxxxxxxx; vkoul@xxxxxxxxxx; > lars@xxxxxxxxxx > Subject: RE: [RFC PATCH 2/4] ASoC: soc-generic-dmaengine-pcm: > Add custom prepare and submit function > > > > > -----Original Message----- > > From: Shevchenko, Andriy <andriy.shevchenko@xxxxxxxxx> > > Sent: 18 November 2020 10:51 PM > > To: Sia, Jee Heng <jee.heng.sia@xxxxxxxxx> > > Cc: Sit, Michael Wei Hong <michael.wei.hong.sit@xxxxxxxxx>; > > alsa-devel@alsa- project.org; tiwai@xxxxxxxx; > broonie@xxxxxxxxxx; > > pierre- louis.bossart@xxxxxxxxxxxxxxx; Rojewski, Cezary > > <cezary.rojewski@xxxxxxxxx>; liam.r.girdwood@xxxxxxxxxxxxxxx; > > vkoul@xxxxxxxxxx; lars@xxxxxxxxxx > > Subject: Re: [RFC PATCH 2/4] ASoC: soc-generic-dmaengine- > pcm: Add > > custom prepare and submit function > > > > On Wed, Nov 18, 2020 at 02:34:22AM +0200, Sia, Jee Heng > wrote: > > > > From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> > > > > Sent: 17 November 2020 11:51 PM > > > > On Tue, Nov 17, 2020 at 04:03:48PM +0800, Michael Sit Wei > Hong wrote: > > > > > Enabling custom prepare and submit function to > overcome DMA limitation. > > > > > > > > > > In the Intel KeemBay solution, the DW AXI-based DMA > has a > > > > > limitation on the number of DMA blocks per transfer. In > the case > > > > > of 16 bit audio ASoC would allocate blocks exceeding the > DMA block limitation. > > > > > > > > I'm still not sure the hardware has such a limitation. > > > > > > > > The Synopsys IP supports linked list (LLI) transfers and I > hardly > > > > can imagine the list has any limitation. Even though, one can > > > > always emulate LLI in software how it's done in the > DesignWare AHB DMA driver. > > > > > > > > I have briefly read chapter 4.6 "AXI_DMA" of Keem Bay TRM > and > > > > didn't find any errata or limits like this. > > > [>>] Intel KeemBay datasheet can be found at below link: > > > > https://www.intel.com/content/www/us/en/secure/design/con > fidential/p > > > ro > > > ducts-and-solutions/processors-and-chipsets/keem- > bay/technical-libra > > > ry .html?grouping=EMT_Content%20Type&sort=title:asc > > > Pg783, "Programmable transfer length (block length), max > 1024". > > > Sub-list can't > > exceed 1024 blocks. > > > BTW, I think the 16bits audio could be a confusion because it is > not > > > about the > > number of bits, but rather the constraint of the block length. > Base on > > my understanding, Audio needs a period larger than 10ms, > regardless of the bit depth. > > > The questions here are: > > > 1. Should DMAEngine expose a new API to constraint the > block_length > > > (instead of > > size in bytes)? > > > 2. Should DMA client re-split the linked-list before passing the > > > linked-list to > > DMAEngine. > > > 3. Should DMA controller driver re-split the linked-list before > execution. > > > > Since we have DMA slave capabilities, the consumer may ask > for them > > and prepare the SG list accordingly. > > > > Above limitation is a block size (value of 1023 is a maximum, > meaning > > 1024 maximum items in the block of given transfer width). So, > like > > DesignWare DMA > > (AHB) has up to 4095 (but I saw hardware with 2047) or iDMA > 32- and > > 64-bit have 131071. There is no limitation for amount of blocks > of > > given maximum length in the LLI! > > > > No hacks are needed, really. > [>>] Hi All, can we have the agreement that DMA clients should > optimize the linked-list [>>] by retrieve the DMA capabilities from > the DMA controller? > [>>] I noticed that Vinod voted #3 but Andy voted #2. > [>>] We need your decision to move on. > > > > -- > > With Best Regards, > > Andy Shevchenko > > Hi everyone, Is there anymore comment on this RFC? We will be using the ASoC framework to split the linked-list, since resplitting the linked-list in DMA is a no go. If there isn't any more comments, we will push these patches for review and merging. Thanks, Regards, Michael
