Hi Arnd, Any comments? Please reply when you see the email since we want this eSDHC issue to be fixed soon. All the patches are Freescale-specific and is to fix the eSDHC driver. Could we let them merged first if you were talking about a new way of abstracting getting SoC version. Thanks :) Best regards, Yangbo Lu > -----Original Message----- > From: Scott Wood [mailto:oss@xxxxxxxxxxxx] > Sent: Wednesday, May 11, 2016 11:26 AM > To: Arnd Bergmann; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Cc: Yangbo Lu; linuxppc-dev@xxxxxxxxxxxxxxxx; Mark Rutland; > devicetree@xxxxxxxxxxxxxxx; ulf.hansson@xxxxxxxxxx; Russell King; Bhupesh > Sharma; netdev@xxxxxxxxxxxxxxx; Joerg Roedel; Kumar Gala; linux- > mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Yang-Leo Li; > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; Rob Herring; linux-i2c@xxxxxxxxxxxxxxx; > Claudiu Manoil; Santosh Shilimkar; Xiaobo Xie; linux-clk@xxxxxxxxxxxxxxx; > Qiang Zhao > Subject: Re: [v10, 7/7] mmc: sdhci-of-esdhc: fix host version for T4240- > R1.0-R2.0 > > On Thu, 2016-05-05 at 13:10 +0200, Arnd Bergmann wrote: > > On Thursday 05 May 2016 09:41:32 Yangbo Lu wrote: > > > > -----Original Message----- > > > > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > > > > Sent: Thursday, May 05, 2016 4:32 PM > > > > To: linuxppc-dev@xxxxxxxxxxxxxxxx > > > > Cc: Yangbo Lu; linux-mmc@xxxxxxxxxxxxxxx; > > > > devicetree@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > > > > linux-kernel@xxxxxxxxxxxxxxx; linux-clk@xxxxxxxxxxxxxxx; > > > > linux-i2c@xxxxxxxxxxxxxxx; iommu@lists.linux- foundation.org; > > > > netdev@xxxxxxxxxxxxxxx; Mark Rutland; ulf.hansson@xxxxxxxxxx; > > > > Russell King; Bhupesh Sharma; Joerg Roedel; Santosh Shilimkar; > > > > Yang-Leo Li; Scott Wood; Rob Herring; Claudiu Manoil; Kumar Gala; > > > > Xiaobo Xie; Qiang Zhao > > > > Subject: Re: [v10, 7/7] mmc: sdhci-of-esdhc: fix host version for > > > > T4240- > > > > R1.0-R2.0 > > > > > > > > On Thursday 05 May 2016 11:12:30 Yangbo Lu wrote: > > > > > IIRC, it is the same IP block as i.MX and Arnd's point is this > > > > > won't even compile on !PPC. It is things like this that prevent > > > > > sharing the driver. > > > > > > The whole point of using the MMIO SVR instead of the PPC SPR is so > > > that it will work on ARM... The guts driver should build on any > > > platform as long as OF is enabled, and if it doesn't find a node to > > > bind to it will return 0 for SVR, and the eSDHC driver will continue > > > (after printing an error that should be removed) without the ability > > > to test for errata based on SVR. > > > > It feels like a bad design to have to come up with a different method > > for each SoC type here when they all do the same thing and want to > > identify some variant of the chip to do device specific quirks. > > > > As far as I'm concerned, every driver in drivers/soc that needs to > > export a symbol to be used by a device driver is an indication that we > > don't have the right set of abstractions yet. There are cases that are > > not worth abstracting because the functionality is rather obscure and > > only a couple of drivers for one particular chip ever need it. > > > > Finding out the version of the SoC does not look like this case. > > I'm open to new ways of abstracting this, but can that please be > discussed after these patches are merged? This patchset is fixing a > problem, the existing abstraction is unappealing and not widely adopted, > a new abstraction is not ready, and we're only touching code for our > hardware. > > Oh, and the existing abstraction isn't even "existing". I don't see any > examples where soc_device is being used like this -- or even any way for > a driver (the one consuming the information, not the soc "driver") to get > a reference to the soc_device that's been registered short of searching > for the device object by name -- and you're asking for new functionality > in drivers/base/soc.c. > > > > > I think the first four patches take care of building for ARM, but > > > > the problem remains if you want to enable COMPILE_TEST as we need > > > > for certain automated checking. > > > > > > What specific problem is there with COMPILE_TEST? > > > > COMPILE_TEST is solvable here and the way it is implemented in this > > case (selecting FSL_GUTS from the driver) indeed looks like it works > > correctly, but it's still awkward that this means building the SoC > > specific ID stuff into the vmlinux binary for any driver that uses > > something like that for a particular SoC. > > Please keep in mind that this is a Freescale-specific driver... it's not > as if we're attaching this dependency to common SDHCI code. > > > > > > > > Dealing with Si revs is a common problem. We should have a > > > > > common solution. There is soc_device for this purpose. > > > > > > > > Exactly. The last time this came up, I think we agreed to > > > > implement a helper using glob_match() on the soc_device strings. > > > > Unfortunately this hasn't happened then, but I'd still prefer that > > > > over yet another vendor-specific way of dealing with the generic > issue. > > > > > > soc_device would require encoding the SVR as a string and then > > > decoding the string, which is more complicated and error prone than > > > having platform-specific code test a platform-specific number. > > > > You already need to encode it as a string to register the soc_device, > > No we don't, because we don't already register a soc_device on arm64 or > ppc (and it looks like whatever does get registered on at least some > relevant > arm32 chips is not particularly useful). > > > and the driver just needs to pass a glob string, so the only part that > > is missing is the generic function that takes the string from the > > driver and passes that to glob_match for the soc_device. > > "just" > > And what would the glob look like? > > I'd rather not write kernel code as if it were a shell/Perl script. > > > > And when would it get registered on arm64, which doesn't have > > > platform code? > > > > Whenever the soc driver is loaded, as is the case now. The match > > function can return -EPROBE_DEFER if no SoC device is registered yet. > > That's too late for some places where we need access to SVR, e.g. clock > drivers (which use CLK_OF_DECLARE and are initialized very early, not as > part of the driver model and thus can't defer). Currently we have an > #ifdef CONFIG_PPC for this in drivers/clk/clk-qoriq.c... Maybe we should > have done that here as well, and saved some grief. :-) At least until an > erratum pops up on an ARM-based chip. > > And what happens if we're running on arm32, and thus the arch code > already registered an soc_device with a different (and less useful) > encoding? > > -Scott ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
