linux-kernel - RE: [PATCH V2 1/2] usb: dwc3: Add node to update cache type setting

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Date:   Thu, 25 Jul 2019 02:29:07 +0000
From:   Ran Wang <ran.wang_1@....com>
To:     Rob Herring <robh@...nel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2 1/2] usb: dwc3: Add node to update cache type setting

Hi Rob,

On Thursday, July 25, 2019 04:42 Rob Herring <robh@...nel.org> wrote:
> 
> On Fri, Jul 12, 2019 at 02:42:05PM +0800, Ran Wang wrote:
> > Some Layerscape paltforms (such as LS1088A, LS2088A, etc) encounter
> > USB detect failues when adding dma-coherent to DWC3 node. This is
> > because the HW default cache type configuration of those SoC are not
> > right, need to be updated in DTS.
> >
> > Signed-off-by: Ran Wang <ran.wang_1@....com>
> > ---
> > Change in v2:
> > 	- New file.
> >
> >  Documentation/devicetree/bindings/usb/dwc3.txt | 43
> > ++++++++++++++++++++++++++
> >  1 file changed, 43 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt
> > b/Documentation/devicetree/bindings/usb/dwc3.txt
> > index 8e5265e..7bc1cef 100644
> > --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> > +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> > @@ -110,6 +110,43 @@ Optional properties:
> >   - in addition all properties from usb-xhci.txt from the current directory are
> >     supported as well
> >
> > +* Cache type nodes (optional)
> > +
> > +The Cache type node is used to tell how to configure cache type on 4
> > +different transfer types: Data Read, Desc Read, Data Write and Desc
> > +write. For each treasfer type, controller has a 4-bit register field
> > +to enable different cache type. Quoted from DWC3 data book Table 6-5
> Cache Type Bit Assignments:
> > +----------------------------------------------------------------
> > +MBUS_TYPE| bit[3]       |bit[2]       |bit[1]     |bit[0]
> > +----------------------------------------------------------------
> > +AHB      |Cacheable     |Bufferable   |Privilegge |Data
> > +AXI3     |Write Allocate|Read Allocate|Cacheable  |Bufferable
> > +AXI4     |Allocate Other|Allocate     |Modifiable |Bufferable
> > +AXI4     |Other Allocate|Allocate     |Modifiable |Bufferable
> > +Native   |Same as AXI   |Same as AXI  |Same as AXI|Same as AXI
> > +----------------------------------------------------------------
> > +Note: The AHB, AXI3, AXI4, and PCIe busses use different names for
> > +certain signals, which have the same meaning:
> > +  Bufferable = Posted
> > +  Cacheable = Modifiable = Snoop (negation of No Snoop)
> 
> This should all be implied from the SoC specific compatible strings.

Did you mean I could implement a soc driver which can be matched by compatible of 'fsl,ls1088a-dwc3' which will pass known bus type to DWC3 driver? If yes, how to pass?

Or I need to add a property snps,mbus_type="AXI3" to DWC3 node, which will co-work with property  transfer_type-datard = "cacheable" to set cache type properly?

Thanks & Regards,
Ran