[0/2] i.MX GPC DMA warning fixes

Message

Lucas Stach Sept. 6, 2019, 10:33 a.m. UTC

Hi all,

those two patches get rid of an annoying boot warning on all i.MX6+
devices, as the generic OF DMA code tries to forcefully configure the
DMA capabilities for the virtual GPX power domain devices, which will
never do any DMA.

This solution isn't the most elegant, as we are making up a 0 DMA mask
to silence the warning instead of skipping the DMA configuration
completely. A previous submission of this change for just the GPC v1 [1]
was shot down for this reason. But then we haven't made any progress in
fixing this in a better way, as other systems depend on the forceful
OF DMA configuration to work correctly. So we are stuck between a rock
and a hard place here.

IMHO we should accept the slight uglyness of this solution in order to
get rid of the warning now, as it is confusing users into thinking their
kernel configuration or system setup is faulty, while everything is
perfectly in order.

Regards,
Lucas

[1] https://patchwork.kernel.org/patch/10621589/

Lucas Stach (2):
  soc: imx: gpc: set DMA mask for PD platform devices
  soc: imx: gpcv2: set DMA mask for PD platform devices

 drivers/soc/imx/gpc.c   | 1 +
 drivers/soc/imx/gpcv2.c | 1 +
 2 files changed, 2 insertions(+)

Comments

Shawn Guo Oct. 6, 2019, 2:06 a.m. UTC | #1

On Fri, Sep 06, 2019 at 12:33:59PM +0200, Lucas Stach wrote:
> Hi all,
> 
> those two patches get rid of an annoying boot warning on all i.MX6+
> devices, as the generic OF DMA code tries to forcefully configure the
> DMA capabilities for the virtual GPX power domain devices, which will
> never do any DMA.
> 
> This solution isn't the most elegant, as we are making up a 0 DMA mask
> to silence the warning instead of skipping the DMA configuration
> completely. A previous submission of this change for just the GPC v1 [1]
> was shot down for this reason. But then we haven't made any progress in
> fixing this in a better way, as other systems depend on the forceful
> OF DMA configuration to work correctly. So we are stuck between a rock
> and a hard place here.
> 
> IMHO we should accept the slight uglyness of this solution in order to
> get rid of the warning now, as it is confusing users into thinking their
> kernel configuration or system setup is faulty, while everything is
> perfectly in order.
> 
> Regards,
> Lucas
> 
> [1] https://patchwork.kernel.org/patch/10621589/
> 
> Lucas Stach (2):
>   soc: imx: gpc: set DMA mask for PD platform devices
>   soc: imx: gpcv2: set DMA mask for PD platform devices

Please copy Arnd for comments.

Shawn

> 
>  drivers/soc/imx/gpc.c   | 1 +
>  drivers/soc/imx/gpcv2.c | 1 +
>  2 files changed, 2 insertions(+)
> 
> -- 
> 2.20.1
>