Hi Simon,
On Thu, 20 Nov 2014 16:44:22 +0000 Simon Glass <[email protected]> wrote: > Hi Masahiro, > > On 19 November 2014 09:21, Masahiro Yamada <[email protected]> wrote: > > Hi Simon, > > > > > > > > On Tue, 18 Nov 2014 14:37:33 +0000 > > Simon Glass <[email protected]> wrote: > > > >> Hi Masahiro, > >> > >> On 18 November 2014 12:51, Masahiro Yamada <[email protected]> > >> wrote: > >> > Hi Simon, > >> > > >> > > >> > > >> > On Mon, 17 Nov 2014 18:17:43 +0000 > >> > Simon Glass <[email protected]> wrote: > >> > > >> >> Hi Masahiro, > >> >> > >> >> On 17 November 2014 08:19, Masahiro Yamada <[email protected]> > >> >> wrote: > >> >> > The driver model provides two ways to pass the device information, > >> >> > platform data and device tree. Either way works to bind devices and > >> >> > drivers, but there is inconsistency in terms of how to pass the > >> >> > pre-reloc flag. > >> >> > > >> >> > In the platform data way, the pre-reloc DM scan checks if each driver > >> >> > has DM_FLAG_PRE_RELOC flag (this was changed to use U_BOOT_DRIVER_F > >> >> > just before). That is, each **driver** has the pre-reloc attribute. > >> >> > > >> >> > In the device tree control, the existence of "u-boot,dm-pre-reloc" is > >> >> > checked for each device node. The driver flag "DM_FLAG_PRE_RELOC" is > >> >> > never checked. That is, each **device** owns the pre-reloc attribute. > >> >> > > >> >> > Drivers should generally work both with platform data and device tree, > >> >> > but this inconsistency has made our life difficult. > >> >> > >> >> I feel we should use device tree where available, and only fall back > >> >> to platform data when necessary (no device tree available for > >> >> platform, for example). > >> > > >> > No, it is true that device tree is a useful tool, but it should be > >> > optional. > >> > > >> > All the infrastructures of drivers must work perfectly without device > >> > tree. > >> > > >> > The device tree is just one choice of how to give device information. > >> > > >> > >> Which platform(s) are we talking about here? > > > > > > I am talking about the general design policy of drivers > > in U-Boot and Linux. > > Well Linux has moved away from platform data, right? > > > > > > > > >> > > >> > > >> >> > > >> >> > This commit abolishes "u-boot,dm-pre-reloc" property because: > >> >> > > >> >> > - Having a U-Boot specific property makes it difficult to share the > >> >> > device tree sources between Linux and U-Boot. > >> >> > > >> >> > - The number of devices is generally larger than that of drivers. > >> >> > Each driver often has multiple devices with different base > >> >> > addresses. It seems more reasonable to add the pre-reloc attribute > >> >> > to drivers than devices. > >> >> > >> >> The inability for platform data to specify which devices need to be > >> >> pre-relocation is certainly a limitation. But I'm not sure that the > >> >> solution is to remove that feature from the device tree. Prior to > >> >> relocation memory may be severely limited. Things like GPIO and serial > >> >> can create quite a few devices (e.g. Tegra has 16 for GPIO and 4 for > >> >> serial), but only a subset may be needed before relocation (on Tegra > >> >> only 2!). > >> >> > >> >> I'm actually pretty comfortable with platform data having a limited > >> >> subset of functionality, since I believe most platforms will use > >> >> device tree for one reason or another. > >> >> > >> >> Thoughts? > >> >> > >> > > >> > No, it is not justified to compel to use device tree > >> > unless Linux is the target OS. > >> > > >> > Even in Linux, limited numbers of architrectures use device trees. > >> > >> Fair enough, but let's look at this when the case comes up. So far the > >> platforms that use I2C and SPI with DM do use device tree in Linux and > >> probably should do in U-Boot. > > > > OK, so let's think about it when a problem happens. > > > > > > Let's get back talking about this patch. > > If 8/8 is not acceptable, I do not have motivation for 6/8 and 7/8, either. > > > > > > I still believe that the top priority of the design policy is > > to share the same device tree source between U-Boot and Linux. > > Agreed, and we really need to line up so we are using the same source. > I do want to point out that we mostly do, the differences are small. > > > > > I am really unhappy about having such a u-boot specific property. > > > > So, my suggestion is this patch, and one possible alternative is > > to bind all the devices even before relocation. > > Only binding won't use much memory because U-Boot does not probe devices > > until they are actually used. > > Both "u-boot,dm-pre-reloc" and DM_FLAG_PRE_RELOC will go away. > > > > > > What do you think? > > That's a waste of time since we won't use them and the goal is to do > as little as possible before relocation. > > I don't see that the pre-reloc property is a huge problem. In the case > of serial I found a way around it (using aliases). I hope that it will > be possible more generally and we can review that at some point in the > future. There are bigger fish to fry in driver model I think - so many > uclasses to write. OK. I've marked 6/8 thru 8/8 as Rejected. No point for 6/8 and 7/8 without 8/8, I think. Best Regards Masahiro Yamada _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
