Re: [PATCH 1/2] dt-bindings: ufs: qcom: allow 'dma-coherent' property

[Johan Hovold <johan@kernel.org>]

On Mon, Dec 05, 2022 at 04:35:22PM -0600, Rob Herring wrote:
> On Mon, Dec 05, 2022 at 02:12:48PM +0100, Johan Hovold wrote:
> > On Mon, Dec 05, 2022 at 06:30:48PM +0530, Manivannan Sadhasivam wrote:
> > > On Mon, Dec 05, 2022 at 01:27:34PM +0100, Johan Hovold wrote:
> > > > On Mon, Dec 05, 2022 at 05:50:18PM +0530, Manivannan Sadhasivam wrote:
> > > > > On Mon, Dec 05, 2022 at 01:07:16PM +0100, Johan Hovold wrote:
> > > > > > On Mon, Dec 05, 2022 at 05:29:06PM +0530, Manivannan Sadhasivam wrote:
> > > > > > > On Mon, Dec 05, 2022 at 11:08:36AM +0100, Johan Hovold wrote:
> > > > > > > > UFS controllers may be cache coherent and must be marked as such in the
> > > > > > > > devicetree to avoid data corruption.
> 
> Typically, you'd only be doing unnecessary cache flushes without it 
> rather than getting data corruption. However, it is possible this 
> property triggers other system setup or something that would cause 
> problems if not setup right.

You can end up with data corruption, for example, if the kernel remaps
a consistent buffer and writes data through the non-cacheable alias
while the coherent device snoops stale data from the caches.

Johan