On 08/21/2013 01:48 PM, Dinh Nguyen wrote: > On Fri, 2013-08-16 at 16:36 -0600, Stephen Warren wrote: >> On 08/14/2013 10:48 AM, dinguyen@xxxxxxxxxx wrote: >>> From: Dinh Nguyen <dinguyen@xxxxxxxxxx> >>> >>> Add bindings for SD/MMC for SOCFPGA. >> >>> diff --git a/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt >> >>> +* altr,sysmgr: Should be the phandle to the system_mgr node. As this is where >>> + this where the register that controls the CIU clock phases >>> + reside. >> >> On the surface, this binding series seems OK, but I do have a question: >> how is the sysmgr phandle used? >> >> I assume there's some register in this syscon device that resets or >> enables or otherwise controls this MSHC module. How does the code know >> which register it is? The phandle in the altr,sysmgr property would >> usually be followed by a/some cell(s) that encode this information, so >> that the MSHC driver doesn't have to know anything about the layout of >> the syscon registers, and so the sysconf driver doesn't have to know >> anything about the identity of the MSHC client device. > > There is a #define SYSMGR_SDMMCGRP_CTRL_OFFSET that is in > dw_mmc-socfpga.c. This defines the offset from the base address that the > sysmgr phandle will give me. Hmmm. That doesn't sound good. That means that the SDMMC driver knows internal details about some other HW module. It'd be better if either: a) The sysmgr driver was required to provide an API to the SDMMC driver to set up the CIU register as requested. or: b) The CIU register details were represented in DT. Either of these would allow the SDMMC driver to operate unchanged on an SoC with a different sysmgr register layout. -- 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
