On 10 August 2015 at 15:44, Olliver Schinagl <oliver+l...@schinagl.nl> wrote: > Hey Michal, > > > On 10-08-15 13:07, Michal Suchanek wrote: >> >> Hello, >> >>> On 08-08-15 20:45, Olliver Schinagl wrote: >>>> >>>> Hey all, >>>> >>>> Alexandru Gagniuc <mr.nuke.me@...> writes: >>>> >>>>> SPI transfers were limited to one FIFO depth, which is 64 bytes. >>>>> This was an artificial limitation, however, as the hardware can handle >>>>> much larger bursts. To accommodate this, we enable the interrupt when >>>>> the Rx FIFO is 3/4 full, and drain the FIFO within the interrupt >>>>> handler. The 3/4 ratio was chosen arbitrarily, with the intention to >>>>> reduce the potential number of interrupts. >>>>> >>>>> Since the SUN4I_CTL_TP bit is set, the hardware will pause >>>>> transmission whenever the FIFO is full, so there is no risk of losing >>>>> data if we can't service the interrupt in time. >>>>> >>>>> For the Tx side, enable and use the Tx FIFO 3/4 empty interrupt to >>>>> replenish the FIFO on large SPI bursts. This requires more care in >>>>> when the interrupt is left enabled, as this interrupt will continually >>>>> trigger when the FIFO is less than 1/4 full, even though we >>>>> acknowledge it. >>>>> >>>>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...> >>>>> Acked-by: Maxime Ripard <maxime.ripard@...> >>>> >>>> This patch was posted more then a year ago and I think several tree's >>>> carry it. >>>> >>>> I've used this patch in combination with the mmc-spi driver and found no >>>> problems with it in the past year. >>>> >>>> So have my Tested-by: Olliver Schinagl <oli...@schinagl.nl> >>>> >>>> and lets get this patch merged! >>>> >>>> P.S. I have the original patch and can resend it if needed. >>>> <snip> >> >> There are basically two issues with this >> >> 1) it conflicts with DMA support. Do we want this when there is DMA >> support almost complete? > > Well this would affect PIO mode in all cases, so do we want this? I would > think yet in case DMA is not available/disabled?
When will that happen? > > As without this patch, we cannot use something like mmc-spi due to the > restriction of packet size iirc. With DMA we can. And since DMA will be enabled most of the time the non-DMA code will receive little or no testing. >> >> >> 2) it adds support on sun4i but not sun6i. Unfortunately, I do not >> have any sun6i hardware. sun6i has dmaengine in mainline but not the >> dma support in spi. > > Well yeah, I don't have sun6i either so we can't merge something nobody has > tested yet ;) >> >> >> That aside, >> >> have you tested this for small transfers that would not trigger the >> fifo 3/4 full interrupt? > > Well the mmc-spi would also have small transfers, no? I mean it's a little > bit of everything I imagine? I have no idea about mmc spi tbh. I have some mmc sockets lying around but did not try using them and did not look at the protocol. Thanks Michal -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
