On Thu, 2013-08-08 at 14:37 -0600, Stephen Warren wrote: > On 08/08/2013 02:32 PM, Dinh Nguyen wrote: > > On Thu, 2013-08-08 at 14:14 -0600, Stephen Warren wrote: > >> On 08/05/2013 02:43 PM, dinguyen@xxxxxxxxxx wrote: > >>> From: Dinh Nguyen <dinguyen@xxxxxxxxxx> > >>> > >>> Add bindings for SD/MMC for SOCFPGA. > >>> Add "syscon" to the "altr,sys-mgr" binding. > >> > >>> diff --git a/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt > >>> new file mode 100644 > >>> index 0000000..dc14922 > >>> --- /dev/null > >>> +++ b/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt > >>> @@ -0,0 +1,48 @@ > >>> +* Altera SOCFPGA specific extensions to the Synopsis Designware Mobile > >>> + Storage Host Controller > >>> + > >>> +Required Properties: > >>> + > >>> +* compatible: should be > >>> + - "altr,socfpga-dw-mshc": for controllers with Altera SOCFPGA > >>> + specific extensions. > >>> + > >>> +* altr,dw-mshc-ciu-div: Specifies the divider value for the card interface > >>> + unit (ciu) clock. The value should be (n-1). For Altera's SOCFPGA, the divider > >>> + value is fixed at 3, which means parent_clock/4. > >> > >> This feels like something that should be represented using the common > >> clock API; a driver should query the rate of its input clock, and then > >> calculate the MMC block's internal divider based on that (perhaps also > >> call clk_set_rate() on the input clock?). > > > > This means a change to the dw_mmc driver, which I can look into for the > > next round? I have promised Pawel to consolidate the bindings for both > > exynos and socfpga in the next round already. I will also look into > > using the common clock API for the MMC as well. > > > > This patch is the only thing that is preventing from SD/MMC working for > > SOCFPGA in the mainline, can I get your Ack if I look into doing this > > for 3.13 for both the exynos and socfpga driver, and address your latter > > comments? > > The problem is that if the binding supports or requires that property > now, it has to at least support it forever. Given that we're getting > serious about DT ABI now, we should be only introducing DT bindings that > we believe are complete and corrrect, rather than bindings which we > actively expect to be temporary and to change incompatibly later. > Right ok. Then I guess I will have to look into consolidating the bindings sooner rather than later. I went back to look at the driver again, and I think it is doing as you are suggesting: host->bus_hz is getting its input value from the common clock API. "altr,dw-mshc-ciu-div" is specifying the internal divider that is in the SD/MMC IP itself. I guess I'm still not clear on how I can represent the SD/MMC divider in in the context of the common clock API. Dinh -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
