On 04/06/2017 03:24 AM, Simon Glass wrote: > Hi Marek, > > On 5 April 2017 at 15:34, Marek Vasut <[email protected]> wrote: >> On 04/05/2017 05:03 PM, Simon Glass wrote: >>> +Tom >>> >>> Hi Marek, >>> >>> On 5 April 2017 at 04:21, Marek Vasut <[email protected]> wrote: >>>> On 04/05/2017 12:08 PM, Simon Glass wrote: >>>>> Hi Marek, >>>>> >>>>> On 5 April 2017 at 03:35, Marek Vasut <[email protected]> wrote: >>>>>> On 04/05/2017 04:21 AM, Simon Glass wrote: >>>>>>> Hi, >>>>>>> >>>>>>> On 4 April 2017 at 19:26, Kever Yang <[email protected]> wrote: >>>>>>>> Hi Eddie, >>>>>>>> >>>>>>>> >>>>>>>> We should only need to do only one time cache operation for a >>>>>>>> buffer >>>>>>>> >>>>>>>> ready to do DMA transfer, so you need to remove another cache >>>>>>>> invalidate >>>>>>>> >>>>>>>> operation for the same buffer in the same function. >>>>>>> >>>>>>> I think this is a more general problem and might cause issues with >>>>>>> other drivers. So I have sent this patch: >>>>>>> >>>>>>> http://patchwork.ozlabs.org/patch/746917/ >>>>>>> >>>>>> >>>>>> This feels like papering over a problem though ... which will bite you >>>>>> later anyway. >>>>> >>>>> I believe the problem only happens because we have cached zero bytes >>>>> caused by this function. If the driver does the right thing (as dwc2.c >>>>> already does) then everything should be find from then on. >>>> >>>> And I think the driver is where this should be fixed ? That is, the >>>> driver should do the right thing and flush/invalidate caches correctly. >>>> >>>>> Notice that the problem does not happen without driver model, since >>>>> non-DM code in dwc2.c uses BSS for the buffers, which is zeroed with >>>>> the cache off. >>> >>> I'm not sure if you read the long and windy thread with Stefan B but >>> the upshot is that the driver is doing the right thing. >>> >>> If the driver were doing the memset() then you could make a case that >>> we should change the driver, but since DM is doing it and DM is >>> promising that DMA can be used on the buffer, I think the best place >>> for the fix is in DM. The driver should not need to change and neither >>> should any other driver when we convert it to DM. >>> >>> On that last point I really want to avoid having to change the caching >>> behaviour of drivers just to work with DM! >> >> So will the driver work with your patch and without DM ? I don't think >> so, so I think what Eddie's patch does is correct. I'd really like him >> to send a new version and apply that. > > Yes the driver work fine without DM and the code is correct. The > buffer is in BSS in that case and we don't have the cache problem. I > think we would have seen this problem before :-)
I am seeing problems around this code and this patch makes sense to me, so I think this patch should go in as well ... >> >> If this also needs to be fixed in DM, so be it. > > OK. > > Regards, > Simon > -- Best regards, Marek Vasut _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
