Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART

From	Bryan O'Donoghue <pure.logic@nexus-software.ie>
Newsgroups	linux.kernel
Subject	Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART
Date	2016-04-12 18:30 +0200
Message-ID	<rn9mq-1RY-5@gated-at.bofh.it> (permalink)
References	<rloSC-YH-5@gated-at.bofh.it> <rloSD-YH-27@gated-at.bofh.it> <rmM6w-87k-69@gated-at.bofh.it> <rmMpQ-8jk-43@gated-at.bofh.it>
Organization	Nexus Software

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On Mon, 2016-04-11 at 18:51 +0300, Andy Shevchenko wrote:
> On Mon, Apr 11, 2016 at 6:33 PM, Bryan O'Donoghue
> <pure.logic@nexus-software.ie> wrote:
> > On Thu, 2016-04-07 at 23:37 +0300, Andy Shevchenko wrote:
> > 
> > Preface. I tried this on Galileo and it appears to work. I'll do
> > some
> > throughput testing to verify but, initially the results are
> > positive :)
> 
> I submitted (and pushed into my branch) a bit changed version (see my
> v2).
> 
> > > +       lpss->dma_maxburst = 8;
> > 
> > Are these dwords ? If those are bytes then the maxburst value looks
> > small. In the BSP the max burst is 32 bytes.
> 
> max_burst is in items of given size (here is 32 bytes for memory and 
> 8

I haven't read your V2 yet but on this, I'd suggest raising the burst
size to 32 bytes for UART (no higher) we found during bringup that
larger sizes "fall-over and die" but, anything up to 32 bytes is OK -
and therefore you should be able to reduce the number of
bursts/interrupts etc.

---
bod

Thread

[PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-07 22:40 +0200
  Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-04-11 17:40 +0200
    Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-04-11 18:00 +0200
      Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-04-11 18:10 +0200
      Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-04-12 18:30 +0200
        Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-12 18:50 +0200
          Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-04-13 13:30 +0200
            Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-13 14:10 +0200
              Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-04-13 16:40 +0200
                Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-13 16:50 +0200
                Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark  UART Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-04-13 17:30 +0200

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