Messages in this thread | | | Date | Thu, 22 Sep 2011 11:11:47 +0530 | Subject | Re: [PATCH] dmaengine: delete redundant chan_id and chancnt initialization in dma drivers | From | Jassi Brar <> |
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On Thu, Sep 22, 2011 at 5:38 AM, Barry Song <21cnbao@gmail.com> wrote: > 2011/9/21 Jassi Brar <jassisinghbrar@gmail.com>: >> On Fri, Sep 16, 2011 at 3:13 PM, Barry Song <Baohua.Song@csr.com> wrote: >>> dma_async_device_register will re-init chan_id and chancnt, >>> so whatever chan_id and chancnt are set in drivers, they will >>> be re-written by dma_async_device_register. >>> >>> Cc: Nicolas Ferre <nicolas.ferre@atmel.com> >>> Cc: Viresh Kumar <viresh.kumar@st.com> >>> Cc: Vinod Koul <vinod.koul@intel.com> >>> Cc: Piotr Ziecik <kosmo@semihalf.com> >>> Cc: Yong Wang <yong.y.wang@intel.com> >>> Cc: Jaswinder Singh <jassi.brar@samsung.com> >>> Cc: Pelagicore AB <info@pelagicore.com> >>> Signed-off-by: Barry Song <Baohua.Song@csr.com> >>> --- >>> drivers/dma/at_hdmac.c | 5 ++--- >>> drivers/dma/dw_dmac.c | 5 ++--- >>> drivers/dma/intel_mid_dma.c | 2 -- >>> drivers/dma/mpc512x_dma.c | 1 - >>> drivers/dma/pch_dma.c | 2 -- >>> drivers/dma/pl330.c | 2 -- >>> drivers/dma/timb_dma.c | 3 +-- >> >> Apparently .... >> >> drivers/dma/ppc4xx/adma.c >> drivers/dma/ipu/ipu_idmac.c >> still write to chan_id. >> >> drivers/dma/amba-pl08x.c >> drivers/dma/fsldma.c >> drivers/dma/ioat/dma_v2.c >> drivers/dma/ioat/dma.c >> drivers/dma/mpc512x_dma.c >> drivers/dma/shdma.c >> still write to chancnt >> My question was if you really intended to convert only some of the drivers and not others?
>> Most of them are simply a matter of removal, but some seem >> like really depending upon setting them(?) >> >> Anyways, even after you modify those as well, chan_id and chancnt >> are rendered overstaying guests in dmaengine core. Because chan_id >> of each channel would be _precisely_ the order in which the >> _dmac-driver_ added the channel to the 'channels' list. >> >> So if their values are _always_ gonna be just contiguously incrementing >> why need variables for that in the dmaengine api? >> Dmac drivers could use local variables for that. >> >> OTOH, why not chan_id be left solely for use by dmac drivers read by the >> dmaengine only to create sysfs entries ? > > actually i don't like the way dmaengine core handles chan_id. in my > opinion, every dmac only needs to tell dmaengine core the chan_base. > then dmaengine core set the id in a global scale. > > for example, if you have two dmac in system: > dmac0 chan_base 0 > dmac1 chan_base 16 > then core will have chan 0~31 by chan_id from 0 to 31 but not > dmac0chan0~15, dmac1chan0~15. But note the numbering is still decided by the dmac driver - directly or indirectly. That is, if the dmac driver reorder registering of dmac or adding channels to the 'channels' list, the assigned chan_id's would change. So why not rather get rid of chan_id assignment from dmaengine and do explicitly in dmac drivers ? Which I already submitted a patch for https://lkml.org/lkml/2011/7/21/1
> client drivers can request a specific chan_id just like it can request a gpio. No dear. That's not gonna fly if we are to have common client drivers across SoCs.
> now dmac drivers and dmaengine core have repeated chan_id and chancnt, > anyway, it is a problem that should be fixed at first. Correct, chan_id assignment should be completely either in dmaengine or in dmac drivers. But this patch does neither. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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