[U-Boot] UCLASS_MISC bug

[Jean-Jacques Hiblot]

+ Simon Glass


Hi Serguey,

On 15/03/2019 22:55, Sergey Kubushyn wrote:
> I would like to point that this was not a very good idea:
>
> === Cut ===
> --- uboot-imx-next/drivers/misc/misc-uclass.c    2018-12-20 
> 20:35:22.505180339 -0800
> +++ u-boot-imx/drivers/misc/misc-uclass.c    2019-03-13 
> 11:50:19.408982814 -0700
> @@ -68,4 +68,7 @@ int misc_set_enabled(struct udevice *dev
>  UCLASS_DRIVER(misc) = {
>      .id        = UCLASS_MISC,
>      .name        = "misc",
> +#if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)
> +    .post_bind    = dm_scan_fdt_dev,
> +#endif
>  };
> === Cut ===
>
> The problem comes up with all those "glue" layers like e.g. in 
> usb/dwc3 and
> everywhere else.
>
> Those "glues" primarily bind drivers to e.g. USB interfaces like e.g.
> dwc3-generic does. That is where it should stop because glue knows better
> what to bind. However, after glue has bound appropriate drivers to their
> interfaces that post_bind scans FDT again and finds yet another bunch of
> drivers that it binds on top of what glue already bound. This happens 
> e.g.
> with DWC3 drivers that glues bind to interfaces depending on their 
> declared
> roles. However both peripheral and XHCI drivers are compatible with
> "snps,dwc3" so they are bound on top creating a huge mess. Here is a 
> dm tree
> fragment of its action:
>
> === Cut ===
>  phy          0  [ + ]   imx8mq_usb_phy        |-- phy at 381f0040
>  misc         0  [ + ]   imx8m_dwc3_glue       |-- usb at 38100000
>  usb          0  [   ]   imx8m_dwc3_periphera  |   |-- dwc3
>  usb          0  [   ]   xhci-dwc3             |   `-- dwc3
>  phy          1  [   ]   imx8mq_usb_phy        |-- phy at 382f0040
>  misc         1  [   ]   imx8m_dwc3_glue       |-- usb at 38200000
>  usb          1  [   ]   xhci-dwc3             |   |-- dwc3
>  usb          2  [   ]   xhci-dwc3             |   `-- dwc3
> === Cut ===
>
> The glue bound imx8m_dwc3_peripheral to USB0 then post_bind found yet
> another "compatible" driver, xhci-dwc3 and bound it to the same 
> interface.
>
> Then glue bound xhci-dwc3 to USB1 but post_bind found yet another
> "compatible" driver, xhci-dwc3 and bound it again so there are TWO xhci
> drivers bound to the same interface.
>
> This is simplified picture -- I removed "compatible" from my peripheral
> driver so it only comes up once, under USB0. If I leave that "compatible"
> with "snps,dwc3" there everything gets even weirder :(
>
> That diff above is the latest 2019.04-rc3 u-boot-imx-next vs 2019.01-rc
> something release.
>
> We either need some additional special flag to disable that post_bind 
> where
> it is not needed or create a special new class for those binding 
> "glues" or
> this change should be reverted.

We can also see the problem on TI platforms.

Tested with a am57xx evm

JJ

>
> P.S. I'm going to post imx8m USB glue, USB PHY, USB peripheral initial
> drivers probably Monday late night as they still need some cleanup. It 
> all
> works with full Linux Kernel DTS files, picks power domains from there.
>
> Don't know what to do with my board-specific DTS as there is (and 
> probably
> will not be) our board submitted -- it is not secret but used in our 
> devices
> only and not available to the public -- so it doesn't make sense to 
> post a
> full DTS. Will probably send a fragment.
>
> ---
> ******************************************************************
> *  KSI at home    KOI8 Net  < >  The impossible we do immediately.  *
> *  Las Vegas   NV, USA   < >  Miracles require 24-hour notice.   *
> ******************************************************************
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> https://lists.denx.de/listinfo/u-boot