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. Regards, Simon _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
