On 9/27/2013 5:58 AM, Joel Fernandes wrote: > On 09/26/2013 06:13 PM, Olof Johansson wrote: >> On Thu, Sep 26, 2013 at 2:55 PM, Joel Fernandes <joelf@xxxxxx> wrote: >>> HWMOD removal for MMC is breaking edma_start as the events are being manually >>> triggered due to unused channel list not being clear. >>> >>> The above issue is fixed by reading the "dmas" property from the DT node if it >>> exists and clearing the bits in the unused channel list if the dma controller >>> used by any device is EDMA. For this purpose we use the of_* helpers to parse >>> the arguments in the dmas phandle list. >>> >>> Also introduced is a minor clean up of a checkpatch error in old code. >>> >>> Reviewed-by: Sekhar Nori <nsekhar@xxxxxx> >>> Reported-by: Balaji T K <balajitk@xxxxxx> >>> Cc: Sekhar Nori <nsekhar@xxxxxx> >>> Cc: Tony Lindgren <tony@xxxxxxxxxxx> >>> Cc: Olof Johansson <olof@xxxxxxxxx> >>> Cc: Nishanth Menon <nm@xxxxxx> >>> Cc: Pantel Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx> >>> Cc: Jason Kridner <jkridner@xxxxxxxxxxxxxxx> >>> Cc: Koen Kooi <koen@xxxxxxxxxxxxxxxxxxxxx> >>> Signed-off-by: Joel Fernandes <joelf@xxxxxx> >>> --- >>> Just resending this patch after discussing with Sekhar and Olof. >> >> Actually, the patch you talked to me about was v3 of this. It seems >> that you have reposted v6 but labelled it v3. This is very confusing. > > Sorry about this. :-( This is indeed v6. > >>> AM335x is being booted by many users such as the beaglebone community. DT is >>> the only boot method available for all these users. EDMA is required for the >>> operation for many common peripherals in AM335x SoC such as McASP, MMC and >>> Crypto. >>> >>> Although EDMA DT nodes are going in only for 3.13, in reality the kernel has >>> been used for more than a year with EDMA code and out of tree EDMA DTS patches. >>> Hence though the DT nodes are still not in mainline, this patch can be still be >>> considered a critical fix as such and it would be great if it could be included >>> in 3.12-rc release. Thanks. >> >> This is really the root of this problem. If you sit on code out of >> tree for a year, and something breaks that we couldn't even have >> detected since we didn't have the out-of-tree pieces. We'll help you >> the first few times (such as now) but we will eventually stop caring. > > When I started looking at EDMA in June, I noticed that a lot had already been > merged. EDMA DMA Engine driver itself was merged last year, no worries there. > but the long pending list of fixes to be made to the driver had to written and > rewritten multiple times which took a long time. > > Due to this, the EDMA device tree entries could not be merged in fear that doing > so would cause problems such as MMC/SD corruption etc. > >> If I was in a worse mood, then I'd just say that since your users >> already has to have out-of-tree code to even use this functionality, >> they could just add this fix on top of that stack of patches. But I'm >> in a slightly better mood than that and I'll pick it up this time. :) > > Thank you! :) > >>> More details about why this broke an existing feature folks were using: >>> Previously the DMA resources for platform devices were being populated through >>> HWMOD, however with the recent clean ups with HWMOD, this data has been moved >>> to Device tree. The EDMA code though is not aware of this so it fails to fetch >>> the DMA resources correctly which it needs to prepare the unused channel list >>> (basically doesn't properly clear the channels that are in use, in the unused >>> list). >> >> So that we can learn for next time: What should we (as in us >> maintainers and you TI) have done differently to avoid this? > > I think a little on both sides can be improved. > > For TI, a bit more work toward explaining patches better in change logs so that > maintainers understand and are willing to help to get the code upstream would > help. A lot of improvement to internal policies have been made for developing on > upstream, and that's certainly a good thing but there's still more room for > improvement. > > For maintainers, EDMA code would have been kept breathing all these months > (atleast 8 months) if those temporary fixes mentioned above would have been > merged into the kernel instead of not applied. With those fixes in place, dts > could have been enabled and EDMA would be fully working all these months. This > would have certainly made things a lot easier. Rewriting stuff the right way is > OK but if it is a _lot_ of effort, then to keep things alive, merging stuff "for > now" specially if they are one-liners could be made acceptable. Joel, can you give a link to the "one-liner" "temporary fix" that was was not merged? I am unable to put it in context. Thanks, Sekhar -- 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
