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Date: Mon, 19 Aug 2013 18:51:03 +0800 From: Sonic Zhang <sonic.adi@...il.com> To: Giuseppe CAVALLARO <peppe.cavallaro@...com> Cc: netdev <netdev@...r.kernel.org>, adi-buildroot-devel@...ts.sourceforge.net, Sonic Zhang <sonic.zhang@...log.com> Subject: Re: [PATCH] driver:net:stmmac: Disable DMA store and forward mode if platform data force_sf_dma_mode is negative. Hi Giuseppe, On Mon, Aug 19, 2013 at 3:45 PM, Giuseppe CAVALLARO <peppe.cavallaro@...com> wrote: > On 8/19/2013 9:31 AM, Sonic Zhang wrote: >> >> Hi Giuseppe, >> >> On Mon, Aug 19, 2013 at 2:03 PM, Giuseppe CAVALLARO >> <peppe.cavallaro@...com> wrote: >>> >>> Hello Sonic >>> >>> >>> On 8/15/2013 9:37 AM, Sonic Zhang wrote: >>>> >>>> >>>> From: Sonic Zhang <sonic.zhang@...log.com> >>>> >>>> Some synopsys ip implementation doesn't support DMA store and forward >>>> mode, >>>> such as BF60x. So, define force_sf_dma_mode negative to use DMA >>>> thresholds >>>> only. >>> >>> >>> >>> I think that you should not pass the force_sf_dma_mode platform field >>> at all (and it doesn't make sense to force it as negative). >>> To use the threshold you should reset tx_coe. In fact, your HW cannot >>> perform the Hw csum if SF is not available. >>> Note that, the HW cap register (if available) can override (set/reset) >>> tx_coe. >> >> >> Even if I reset tx_coe, the SF mode is still set to RX DMA in current >> stmmac_dma_operation_mode(). SF mode is not supported in both RX DMA >> and TX DMA in Blackfin MAC. > > > yes this is true. the SF is always set for the RX path because I have > never had and known HW w/o RX csum (since the 209). > > So I think the code could be improved to disable/enable the SF also for > the RX path. > > >>> >>> I tested, long time ago, this scenario on old mac w/o HW cap register >>> and w/o SF. >> >> >> Blackfin synopsys MAC IP has the HW cap register with tx_coe set to 1, >> but the HW tx_coe doesn't really work. I have the other patch to >> disable HW tx_coe in board file and override the HW cap register. > > > AFAIK the HW shouldn't be able to perform the csum in HW w/o SF. > > Maybe, an easy way could be to use a new field to force the threshold > mode. This should also remove the csum in HW (IMO) and program the > DMA operation register. > The problem is that HW RX csum works perfectly on Blackfin MAC although the SF mode is not supported in RX DMA. I may need 2 platform fields to force RX DMA threshold and disable HW tx_coe. One field doesn't cover both cases well. Which 2 fields do you prefer? Thanks Sonic -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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