Madhusudhan <madhu.cr@xxxxxx> wrote: >> -----Original Message----- >> From: svenkatr@xxxxxxxxx [mailto:svenkatr@xxxxxxxxx] On Behalf Of >> Venkatraman S >> Sent: Thursday, March 11, 2010 4:52 AM >> To: Madhusudhan >> Cc: linux-mmc@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; >> linux-omap@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH 03/03] omap hsmmc: adaptation of sdma descriptor >> autoloading feature >> >> Madhusudhan <madhu.cr@xxxxxx> wrote: >> >> -----Original Message----- >> >> From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc- >> >> owner@xxxxxxxxxxxxxxx] On Behalf Of Venkatraman S >> >> Sent: Monday, March 01, 2010 5:27 AM >> >> To: linux-mmc@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; >> >> linux-omap@xxxxxxxxxxxxxxx >> >> Subject: [PATCH 03/03] omap hsmmc: adaptation of sdma descriptor >> >> autoloading feature >> >> >> >> Start to use the sDMA descriptor autoloading feature. >> >> For large datablocks, the MMC driver has to repeatedly setup, program >> >> and teardown the >> >> dma channel for each element of the sglist received in >> omap_hsmmc_request. >> >> >> >> By using descriptor autoloading, transfers from / to each element of >> >> the sglist is pre programmed >> >> into a linked list. The sDMA driver completes the entire transaction >> >> and provides a single interrupt. >> >> >> >> Due to this, number of dma interrupts for a typical 100MB transfer on >> the >> >> MMC is >> >> reduced from 25000 to about 400 (approximate). Transfer speeds are >> >> improved by ~5% >> >> (Though it varies on the size of read / write & improves on huge >> >> transfers) >> >> >> >> Descriptor autoloading is available only in 3630 and 4430 (as of now). >> >> Hence normal DMA >> >> mode is also retained. >> >> >> >> Tested on omap4430 sdp. >> >> >> >> Signed-off-by: Venkatraman S <svenkatr@xxxxxx> >> > >> > I don't see any issues with this patch except the concern I had on the >> first >> > patch in the series. Why is that change linked to this series? >> > >> Thanks. The problem was seen only in the context of using descriptor >> load. Would >> you prefer that I post it as a separate patch ? > > My point is why that change is needed for this feature to work? > > When DMA is completed and a callback is received the ch can be freed. Once > TC is received the core is notified of the same. > > Can the first patch be dropped? Or do you see issues? Yes there are issues without this patch when the scatterlist is large (300+ blocks), where the dma completion interrupt is received but the mmc driver hangs waiting for TC. I don't see the issue if I delay the execution of omap_free_dma inside the dma callback. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
