Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH v3 2/2] arm64: dts: Add BRCM IPROC NAND DT node for NS2 | From | Ray Jui <> | Date | Wed, 28 Oct 2015 09:08:02 -0700 |
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On 10/28/2015 2:06 AM, Anup Patel wrote: > > >> -----Original Message----- >> From: Ray Jui [mailto:rjui@broadcom.com] >> Sent: 28 October 2015 06:17 >> To: Brian Norris >> Cc: Anup Patel; David Woodhouse; Linux MTD; Rob Herring; Pawel Moll; Mark >> Rutland; Catalin Marinas; Will Deacon; Sudeep Holla; Ian Campbell; Kumar Gala; >> Scott Branden; Florian Fainelli; Pramod Kumar; Vikram Prakash; Sandeep >> Tripathy; Linux ARM Kernel; Device Tree; Linux Kernel; bcm-kernel-feedback-list >> Subject: Re: [PATCH v3 2/2] arm64: dts: Add BRCM IPROC NAND DT node for >> NS2 >> >> >> >> On 10/27/2015 5:39 PM, Brian Norris wrote: >>> On Tue, Oct 27, 2015 at 05:25:32PM -0700, Ray Jui wrote: >>>> On 10/27/2015 5:19 PM, Brian Norris wrote: >>>>> On Fri, Oct 23, 2015 at 10:46:13AM +0530, Anup Patel wrote: >>>>>> diff --git a/arch/arm64/boot/dts/broadcom/ns2.dtsi >>>>>> b/arch/arm64/boot/dts/broadcom/ns2.dtsi >>>>>> index f603277..9610822 100644 >>>>>> --- a/arch/arm64/boot/dts/broadcom/ns2.dtsi >>>>>> +++ b/arch/arm64/boot/dts/broadcom/ns2.dtsi >>>>>> @@ -212,5 +212,19 @@ >>>>>> compatible = "brcm,iproc-rng200"; >>>>>> reg = <0x66220000 0x28>; >>>>>> }; >>>>>> + >>>>>> + nand: nand@66460000 { >>>>>> + compatible = "brcm,nand-iproc", "brcm,brcmnand- >> v6.1"; >>>>> >>>>> Technically, the binding says you should also have "brcm,brcmnand" >>>>> as a last resort. Otherwise (for the NAND parts): >>>>> >>>> >>>> I believe Anup was seeing issues when both "brcm,nand-iproc" and >>>> "brcm,brcmnand" are present. >>>> >>>> Note "brcm,nand-iproc" invokes 'iproc_nand_probe', which calls >>>> 'brcmnand_probe' in the end. >>>> >>>> "brcm,brcmnand" invokes 'brcmstb_nand_probe', which also calls >>>> 'brcmstb_probe', but without all the prep configuration required for >>>> "brcm,nand-iproc". >>> >>> Ah, I forgot about that problem. That seems like an OF infrastructure >>> issue that could be fixed. We could lump these drivers back together, >>> and make sure that "brcm,nand-iproc" gets the priority in the >>> of_device_id list. >>> >>> Or we could just relax the DT binding. >>> >>> But wait, wouldn't cygnus already have that problem? You're using the >>> binding I suggested in arch/arm/boot/dts/bcm-cygnus.dtsi. >> >> Interestingly, we do not see this problem with Cygnus or NSP, but only on NS2 >> (arm64 based). There may be a difference between how OF devices are >> instantiated between arm and arm64? > > Alternately, it could be also about order in-which platform drivers are matched > for newly created OF device. > >> >>> >>> Oh, and I see we hacked this one in drivers/mtd/nand/brcmnand/Makefile: >>> >>> # link order matters; don't link the more generic brcmstb_nand.o before the >>> # more specific iproc_nand.o, for instance >> >> Yes, I see that too (after sending out my previous email, :)). Maybe >> Anup can help to elaborate on the problem. I'm now getting a bit >> confused on how the problem can surface on NS2. > > I think for a newly created OF devices the Linux device driver framework will > match the platform drivers in the order in which they are registered by module > init functions. Now the order of module init function calls will be based how > the .initcall section is formed by linker and order in which objects are linked. >
Yes, what you said is my understanding as well, but then here is the mystery. This is the link order in brcmnand/Makefile:
1 # link order matters; don't link the more generic brcmstb_nand.o before the 2 # more specific iproc_nand.o, for instance 3 obj-$(CONFIG_MTD_NAND_BRCMNAND) += iproc_nand.o 4 obj-$(CONFIG_MTD_NAND_BRCMNAND) += bcm63138_nand.o 5 obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmstb_nand.o 6 obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmnand.o
Based on the order above, probe from iproc_nand should always be called first if a matching compatible string is found. If so, then why having both compatible strings "brcm,brcmnand" and "brcm,nand-iproc" causes issues for NS2 (I remember it broke smoketest in the past when you submitted the change)? I'm not saying we should have "brcm,brcmnand" for iProc devices, but I don't get why it would cause any issue.
Does the order of the compatible string matter when they are assigned to the same 'compatible' property like this?
compatible = "brcm,nand-iproc", "brcm,brcmnand-v6.1", "brcm,brcmnand";
> IMHO, if multiple platform drivers match given OF device then platform driver > with longest matching compatible string should only be probed. I don't know > how big change this would be for OF framework. > >> >> But in general, I think it's a good idea to relax the requirement in the >> DT binding document to not require "brcm,brcmnand", in the case when >> "brcm,nand-iproc" and "brcm,nand-bcm63138" are present. > > Even I think, it will be good to relax the DT bindings requirement for > BRCM NAND driver. > > Regards, > Anup >
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