On Mon, Oct 03, 2016 at 06:11:23PM +0200, Robert Jarzmik wrote: > Mark Rutland <mark.rutland@xxxxxxx> writes: > > > On Mon, Oct 03, 2016 at 11:05:53AM +0200, Robert Jarzmik wrote: > >> Add a workaround for mainstone, idp and stargate2 boards, for u16 writes > >> which must be aligned on 32 bits addresses. > >> > >> Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx> > >> --- > >> Documentation/devicetree/bindings/net/smsc911x.txt | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/net/smsc911x.txt b/Documentation/devicetree/bindings/net/smsc911x.txt > >> index 3fed3c124411..224965b7453c 100644 > >> --- a/Documentation/devicetree/bindings/net/smsc911x.txt > >> +++ b/Documentation/devicetree/bindings/net/smsc911x.txt > >> @@ -13,6 +13,8 @@ Optional properties: > >> - reg-io-width : Specify the size (in bytes) of the IO accesses that > >> should be performed on the device. Valid value for SMSC LAN is > >> 2 or 4. If it's omitted or invalid, the size would be 2. > >> +- reg-u16-align4 : Boolean, put in place the workaround the force all > >> + u16 writes to be 32 bits aligned > > > > This property name and description is confusing. > > > > How exactly does this differ from having reg-io-width = <4>, which is > > documented immediately above? > > reg-io-width specifies the IO size, ie. how many data lines are physically > connected from the system bus to the lan adapter. > > reg-u16-align4 tells that a specific hardware doesn't support 16 bit writes not > being 32 bits aligned, or said differently that a "store" 16 bits wide on an > address of the format 4*n + 2 deserves a special handling in the driver, while a > store 16 bits wide on an address of the format 4*n can follow the simple casual > case. If I've understood correctly, effectively the low 2 address lines to the device are hard-wired to zero, e.g. a 16-bit access to 4*n + 2 would go to 4*n + 0 on the device? Or is the failure case distinct from that? Do we have other platforms where similar is true? e.g. u8 accesses requiring 16-bit alignment? Thanks, Mark. -- 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
