> -----Original Message----- > From: Russell King - ARM Linux [mailto:linux@xxxxxxxxxxxxxxxx] > Sent: Wednesday, July 04, 2012 3:12 PM > To: N, Mugunthan V > Cc: linux-omap@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: Re: how to specify dma_mask and coherent_dma_mask in hwmod > > On Thu, Jun 07, 2012 at 04:22:17PM +0000, N, Mugunthan V wrote: > > While converting platform device registry to Hwmod for CPSW Ethernet > > driver which is present in AM335X (OMAP2+), I am not finding a way > > to specify dma_mask and coherent_dma_mask. > > Is there a way to specify dma_mask and coherent_dma_mask in hwmod? > > Just remember that we're moving stuff to DMA engine, and that means > the sDMA device has DMA masks, but none of the peripherals which make > use of sDMA should have DMA masks set. > > The reason for this is because the device responsible for accessing > memory is sDMA, not the peripheral device, and therefore any memory > properties for DMA should come from the sDMA device, not the peripheral > device. I agree that properties of DMA should come from sDMA device. In my case (CPSW Ethernet) has a peripheral DMA (davinci_cpdma) which takes care of transferring packet from memory to Ethernet IP and vice versa. For allocating DMA memory space for davinci_cpdma, dma_alloc_coherent is used which requires dma_masks to be specified for the device. To pass the dma_masks to the device following ways can be followed. 1. Extend omap_device_build arguments to hold dma_mask and coherent_dma_mask which will affect all other devices which uses omap_device_build api. 2. Hardcode the dma_mask and coherent_dma_mask in omap_device_build with 0xffffffff which can harm other devices 3. Specify the dma_mask and coherent_dma_mask after creating the device as done in musb device. http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=arch/a rm/mach-omap2/usb-musb.c;h=c4a576856661014ea3bec9acc70f80e32d62c33b;hb=HEAD Regards, Mugunthan V N -- 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
