On Tue, May 17, 2011 at 12:27 AM, Philip Rakity <prakity@xxxxxxxxxxx> wrote: > > On May 16, 2011, at 7:02 PM, zhangfei gao wrote: > >> On Mon, May 16, 2011 at 9:51 AM, Philip Rakity <prakity@xxxxxxxxxxx> wrote: >>> >>> On May 15, 2011, at 11:26 PM, zhangfei gao wrote: >>> >>>> On Sat, May 14, 2011 at 1:01 PM, Philip Rakity <prakity@xxxxxxxxxxx> wrote: >>>>> >>>>> On May 13, 2011, at 10:11 PM, zhangfei gao wrote: >>>>> >>>>>> On Fri, May 13, 2011 at 9:47 PM, Chris Ball <cjb@xxxxxxxxxx> wrote: >>>>>>> Hi, >>>>>>> >>>>>>> On Thu, May 12 2011, Philip Rakity wrote: >>>>>>>> All other platform specific code is in the host/ directory. >>>>>>>> >>>>>>>> This moves it to arch/arm >>>>>>>> >>>>>>>> If that is the direction the group wants to go in --> then the patch >>>>>>>> is fine provided the mmc group can review the patches. Otherwise they >>>>>>>> are handled by the arm maintainer. >>>>>>> >>>>>>> Thanks. Wolfram, do you have any ideas on what the best design is for >>>>>>> these SoC-specific changes to sdhci-pxa? >>>>>>> >>>>>>> - Chris. >>>>>> >>>>>> The code in arch/arm is >>>>>> 1. Accessing private register, take pxa910 and mmp2 we want to support >>>>>> as example, there are several private registers differece, though they >>>>>> are same ip, with same issues and quirk. >>>>>> 2. Handle platform difference, for example, mmp2 used in two different >>>>>> platform, one use wp pin, the other does not. >>>>> >>>>> The situation is a little more complicated. >>>> >>>> The interface is used for long time among mmp2, pxa910 and mmp3. >>>> Also could be used for new controller with minor register difference >>>> but same ip, without adding new specific driver. >>> >>> applies to both approaches. The mmp2 specific code can be applied to other marvell >>> platforms that share the same controller. Just change Kconfig and the Makefile to use >>> the mmp2 code. The name of the file is not the important thing. It is what it does. >>> >>> The pxa168 and pxa910 code are a little less sharable due to io accessors and some >>> other quirks. >>> >>> For other following the discussion we are probably talking about 100 liens of code. >>> >>> The philosophical location of where the code belongs for host specific drivers is >>> to me more important. >>> >>> Is it in arch/arm and not directly visible to the mmc list or is it like all other platform drivers >>> in drivers/mmc/host. >> >> The code handle several register difference are located at >> arch/arm/mach-mmp/mmp2.c is for mmp2 >> arch/arm/mach-mmp/pxa910.c is for pxa910 serious, >> arch/arm/mach-mmp/mmp3.c is for mmp3 serious, considering there may >> still registers changing. >> >> The board difference are directly put in board.c >> For example ttc_dkb do not use wp pin, so get_ro is provided. > > embedding the code in these chip files stops code sharing. For example, > mmp3 has same controller as mmp2. If register are totally same, they can share. If there is minor difference with chip upgrading, they can put in different file. >> >>> >>> >>> >>>> >>>>> >>>>> pxa168 and pxa910 share (almost) the same IP The are both based on SD 2.0 >>>>> controller spec with extensions. The pxa910 controller has fixes to the >>>>> pxa168 controller. They share the same private registers that allow support >>>>> for clock gating and timing adjustments. >>>>> >>>>> mmp2 is based on SD 3.0 spec. The private register space is different. >>>>> >>>>> mmc/host/Kconfig takes no account of these differences. mmp2 and pxa168/910 >>>>> cannot co-exist. What is currently submitted does not work. One cannot >>>>> compile mmp2 and pxa910 nor would they work if one could. >>>>> >>>>> Mark Brown and I submitted patches to fix this. We added code to the host/ directory >>>>> that took into account these differences. It provided a common interface layer >>>>> that then used platform specific code in the host/ directory to handle the different >>>>> behavior. >>>>> >>>>> Arng Bergmann provided advice and reviewed the patches to allow explicit selection of the >>>>> pxa familty controller and board. Based on this comments we submitted a patch >>>>> to allow selection if the appropriate SoC. >>>>> >>>>> These are two approaches. >>>>> >>>>>> >>>>>> Thanks >>>>>>> -- >>>>>>> Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/> >>>>>>> One Laptop Per Child >>>>>>> >>>>> >>>>> >>> >>> > > -- 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
