Hello Simon, From: Simon Horman [mailto:horms@xxxxxxxxxxxx] Sent: 24 November 2016 10:18 > Hi Chris, > > On Thu, Nov 24, 2016 at 10:05:08AM +0000, Chris Paterson wrote: > > Hello Simon, > > > > From: Simon Horman [mailto:horms@xxxxxxxxxxxx] > > Sent: 23 November 2016 14:30 > > > On Wed, Nov 23, 2016 at 02:18:13PM +0100, Marc Kleine-Budde wrote: > > > > On 11/23/2016 01:14 PM, Chris Paterson wrote: > > > > > This patch series adds CAN and CAN FD support to the r8a7796. > > > > > > > > > > Based on renesas-devel-20161122-v4.9-rc6. > > > > > > > > > > Chris Paterson (3): > > > > > arm64: dts: r8a7796: Add CAN external clock support > > > > > arm64: dts: r8a7796: Add CAN support > > > > > arm64: dts: r8a7796: Add CAN FD support > > > > > > > > > > .../devicetree/bindings/net/can/rcar_can.txt | 12 +++-- > > > > > .../devicetree/bindings/net/can/rcar_canfd.txt | 12 +++-- > > > > > arch/arm64/boot/dts/renesas/r8a7796.dtsi | 61 > > > ++++++++++++++++++++++ > > > > > 3 files changed, 75 insertions(+), 10 deletions(-) > > > > > > > > For all three: > > > > > > > > Acked-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> > > > > > > > > Who takes this series? > > > > > > I would like to see these patches split up so that the > > > .../devicetree/bindings/ portions can go through you whole the > > > arch/arm64/boot/dts/renesas/ portions go thorugh my renesas tree. > > > > Okay, will do. > > Thanks. > > > > Regarding the arch/arm64/boot/dts/renesas/ portion, I would like > > > some consideration given to what effect enabling memory above 4Gb > > > (64bit > > > addressing) would have. > > > > Can you give me some guidance here? I'm not sure what you're referring > > to. As far as I know the DT reg definition here is 64-bit, or are you > > referring to DMA usage? If the later, neither CAN driver uses DMA. > > Sorry for not being clearer. > > What I would like to know is if there are any problems in the CAN driver or > hardware that would prevent it from functioning with memory that requires > 64bit addressing present. > > If the CAN hardware cannot use DMA then DMA doesn't need to be taken > into account. But if it DMA could be enabled in future for CAN, for example > after some driver enhancements, then it would be good to know if 64bit > memory can be supported - if not it would imply DMA cannot be enabled. Thank you for the clarification. The CAN interface for r8a7795/6 does not support DMA. With CAN FD there is currently a H/W issue that means DMA is unusable. Potentially this issue could be fixed in the future and DMA support could be added to the driver. If this happens I can see no reason why the CAN FD IP wouldn't be able to handle DMA transfers when using 64bit addressing. > > As for non-DMA mode, will this function if memory above 4G is present? > If not then in theory such memory couldn't be enabled if the CAN driver is > enabled. This is my main concern. Yes, it functions fine. We have already tested this with the Renesas v3.3.2 BSP with >4Gb memory. If this is explanation okay for you, I'll proceed with a v2 splitting off the DT bindings documentation. Kind regards, Chris > > Does the above help? -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
