* Tony Lindgren <tony@xxxxxxxxxxx> [181125 01:07]: > * Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx> [181124 20:10]: > > On Fri, Nov 23, 2018 at 08:52:15PM +0200, Aaro Koskinen wrote: > > > Hi, > > > > > > On Fri, Nov 23, 2018 at 02:35:04PM +0200, Peter Ujfalusi wrote: > > > > On 22/11/2018 17.12, Russell King - ARM Linux wrote: > > > > > I'm also not sure about this: > > > > > > > > > > if (cpu_is_omap15xx()) > > > > > end++; > > > > > > > > > > in dma_dest_len() - is that missing from the omap-dma driver? It looks > > > > > like a work-around for some problem on OMAP15xx, but I can't make sense > > > > > about why it's in the UDC driver rather than the legacy DMA driver. > > > > > > > > afaik no other legacy drivers were doing similar thing, this must be > > > > something which is needed for the omap_udc driver to fix up something? > > > > > > Here's the patch that added it: https://marc.info/?l=linux-omap&m=119634396324221&w=2 > > > > > > "Make DMA-OUT behave on the 1510 ... the 1510 CPC register was just > > > off-by-one with respect to the 1611 CDAC" > > > > ... which suggests that's a problem with the CPC register itself, and > > we should fix that in the DMAengine driver rather than the USB gadget > > driver. > > > > Tony, any input on this? > > Yeah that sounds like some hardware work-around for 15xx as described > in the DMA_DEST_LAST macro reading CSAC on 15xx instead of CDAC. Seems > like it should be done in the dmaengine driver.. My guess is that other > dma users never needed to read CSAC register? And it looks like for 15xx we have CPC and CSAC both at offset 0x18 in arch/arm/mach-omap1/dma.c, seems like the dma driver is missing handling for the CPC register that's there only for 15xx. Regards, Tony
