Greg, Thanks. I'll change the call to kmm_malloc() or kmm_memalign() and see if that works too.
cheers adam On Tue, Jul 7, 2020 at 9:03 PM spudaneco <spudan...@gmail.com> wrote: > I don't know anything about the DMA, but you should not call calloc() from > within the OS. That does not work in all configurations.Instead include > nuttx/kmalloc,h and call kmm_malloc(). If you want aligned memory, call > kmm_memalgn().Sent from Samsung tablet. > -------- Original message --------From: Adam Feuer <a...@adamfeuer.com> > Date: 7/7/20 9:40 PM (GMT-06:00) To: dev@nuttx.apache.org Subject: > driver question about memory and calloc Hi,I am getting the SAMA5D27 SDMMC > SD Card driver pull request ready. There'sone small issue I'm working on, > though. There's a place in the driverinitialization where I calloc() some > memory– 466 bytes. DMA data transferswhile reading from files times out if > I don't have the calloc() in there.With the memory allocated, everything > works fine. Nothing writes to thisblock of memory– I memset it and examined > it before, during, and aftertransfers using GDB. It's just an unused block > of memory.I'm trying to find out if other amounts of memory work– smaller > than about100 bytes doesn't work, and I know it works reliably at 466 > bytes. I'lltrack the exact number down tomorrow.But my question is, why > does this work? The driver datasheets< > http://ww1.microchip.com/downloads/en/devicedoc/ds60001476b.pdf>don'tmention > that the chip needs aligned memory for its buffers, and the Atmeland U-Boot > drivers don't use aligned memory. And since nothing isoverwriting the > memory, what is the calloc() doing to prevent the SDMMC DMAengine from > completing the transfer?If anyone has seen behavior like this, I'd love to > know it. I'd like totake this otherwise useless code out, or at least know > why I need it.Link to the specific line of code in sam_sdmmc.c< > https://github.com/starcat-io/incubator-nuttx/blob/feature/sama5d27-sdmmc-support/arch/arm/src/sama5/sam_sdmmc.c#L3737>cheersadam-- > Adam Feuer <a...@adamfeuer.com> -- Adam Feuer <a...@starcat.io>
