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Date:	Fri, 19 Sep 2014 16:49:57 +0200
From:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:	Dinh Nguyen <dinguyen@...nsource.altera.com>
Cc:	paulz@...opsys.com, gregkh@...uxfoundation.org, balbi@...com,
	dinh.linux@...il.com, swarren@...dotorg.org, matthijs@...in.nl,
	r.baldyga@...sung.com, jg1.han@...sung.com,
	sachin.kamat@...aro.org, ben-linux@...ff.org,
	dianders@...omium.org, kever.yang@...k-chips.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 01/12] usb: dwc2: Update Kconfig to support dual-role


Hi,

On Thursday, September 18, 2014 10:54:24 AM Dinh Nguyen wrote:
> Hi Bartlomiej,
> 
> On 09/12/2014 10:49 AM, Bartlomiej Zolnierkiewicz wrote:
> > 
> > [ added linux-kernel ML to cc: ]
> > 
> > Hi,
> > 
> > On Tuesday, August 26, 2014 11:19:52 AM dinguyen@...nsource.altera.com wrote:
> >> From: Dinh Nguyen <dinguyen@...nsource.altera.com>
> >>
> >> Update DWC2 kconfig and makefile to support dual-role mode. The platform
> >> file will always get compiled for the case where the controller is directly
> >> connected to the CPU. So for loadable modules, only dwc2.ko is needed.
> > 
> > Kconfig and Makefile changes should be done after (or at the same time as)
> > driver code itself is modified to support dual-role mode.  Each individual
> > patch of the patchset should be correct itself (not cause any breakages)
> > in order to keep the whole patchset bisectable.
> > 
> 
> Paulz mentioned this in v1 of this patch series and ever since then, I
> have been careful to test each patch on it's own, and each version since
> then has passed 0-Day kbuild testing. But I may have missed something in
> v4. Will try to move the edits to Kconfig/Makefile to end for v5.
> 
> >> Signed-off-by: Dinh Nguyen <dinguyen@...nsource.altera.com>
> >> Acked-by: Paul Zimmerman <paulz@...opsys.com>
> >> ---
> >> v3: Add USB_GADGET=y and USB_GADGET=USB_DWC2 for peripheral and dual-role
> >>     config options.
> >> v2: Remove reference to dwc2_gadget
> >> ---
> >>  drivers/usb/dwc2/Kconfig  | 63 +++++++++++++++++++++++++++--------------------
> >>  drivers/usb/dwc2/Makefile | 21 ++++++++--------
> >>  2 files changed, 47 insertions(+), 37 deletions(-)
> >>
> >> diff --git a/drivers/usb/dwc2/Kconfig b/drivers/usb/dwc2/Kconfig
> >> index f93807b..4396a1f 100644
> >> --- a/drivers/usb/dwc2/Kconfig
> >> +++ b/drivers/usb/dwc2/Kconfig
> >> @@ -1,40 +1,29 @@
> >>  config USB_DWC2
> >> -	bool "DesignWare USB2 DRD Core Support"
> >> +	tristate "DesignWare USB2 DRD Core Support"
> >>  	depends on USB
> >>  	help
> >>  	  Say Y here if your system has a Dual Role Hi-Speed USB
> >>  	  controller based on the DesignWare HSOTG IP Core.
> >>  
> >> -	  For host mode, if you choose to build the driver as dynamically
> >> -	  linked modules, the core module will be called dwc2.ko, the PCI
> >> -	  bus interface module (if you have a PCI bus system) will be
> >> -	  called dwc2_pci.ko, and the platform interface module (for
> >> -	  controllers directly connected to the CPU) will be called
> >> -	  dwc2_platform.ko. For gadget mode, there will be a single
> >> -	  module called dwc2_gadget.ko.
> >> -
> >> -	  NOTE: The s3c-hsotg driver is now renamed to dwc2_gadget. The
> >> -	  host and gadget drivers are still currently separate drivers.
> >> -	  There are plans to merge the dwc2_gadget driver with the dwc2
> >> -	  host driver in the near future to create a dual-role driver.
> >> +	  If you choose to build the driver as dynamically
> >> +	  linked modules, a single dwc2.ko(regardless of mode of operation)
> > 
> > minort nitpick: " " is missing after dwc2.ko
> > 
> >> +	  will get built for both platform IPs and PCI.
> > 
> > Why do you want ot merge both platform and PCI drivers into one?
> > 
> > To do it properly you need to modify module_init/exit() of the final
> > module to properly handle both PCI and platform devices.  It should
> > be easier to leave separate dwc2_pci/platform drivers and just put
> > the common code into dwc2.ko.
> 
> I need to rework to the comment. I think it should say, "will get built
> for either platform IPs or PCI." I am not merging both platform and PCI
> drivers into one.

OK, it is good to hear that.

Unfortunately after second look there are even more problems with Kconfig
changes, please see below.

> > 
> >>  if USB_DWC2
> >>  
> >> +choice
> >> +	bool "DWC2 Mode Selection"
> >> +	default USB_DWC2_DUAL_ROLE if (USB && USB_GADGET)
> >> +	default USB_DWC2_HOST if (USB && !USB_GADGET)
> >> +	default USB_DWC2_PERIPHERAL if (!USB && USB_GADGET)

Previously it was possible to have following functionalities in
one kernel (for multiplatform kernels):

- host PCI support
- host platform support
- gadget platform support

Now mode selection will determine the used mode for combined
host+gadget platform driver.  It is no longer possible to have
host platform and gadget platform support in one kernel.

Also there is only one mode selection for both PCI and platform
drivers so it is no longer possible to have both gadget platform
support and host PCI support in one kernel.

I think it would be the best to replace global mode selection
choice option with just two independent suboptions for combined
host+gadget platform driver which will enable host and gadget
support to be compiled into the driver (you would need to enable
both for dual role support).  The actual selection of the mode
used should be done at runtime using device tree.

[ Host PCI support can be left as independent host only driver
  for now until it also gets proper gadget support (according to
  comments from Paul). ]

> >> +
> >>  config USB_DWC2_HOST
> >> -	tristate "Host only mode"
> >> +	bool "Host only mode"
> >>  	depends on USB
> >>  	help
> >>  	  The Designware USB2.0 high-speed host controller
> >> -	  integrated into many SoCs.
> >> -
> >> -config USB_DWC2_PLATFORM
> >> -	bool "DWC2 Platform"
> >> -	depends on USB_DWC2_HOST
> >> -	default USB_DWC2_HOST
> >> -	help
> >> -	  The Designware USB2.0 platform interface module for
> >> -	  controllers directly connected to the CPU. This is only
> >> -	  used for host mode.
> >> +	  integrated into many SoCs. Select this option if you want the
> >> +	  driver to operate in Host-only mode.
> >>  
> >>  config USB_DWC2_PCI
> >>  	bool "DWC2 PCI"
> > 
> > Why have you left this option into middle of 'choice' selection?
> 
> Will move...
> 
> > 
> > You've also left the "depends on USB_DWC2_HOST && PCI" unmodified
> > which causes DWC2 PCI support to show up only if "Host only mode"
> > is selected (it is not available if "Dual Role mode" is selected).
> > 
> 
> Does PCI support gadget? I left it unmodified because I didn't think the
> PCI driver supported Gadget.
> 
> 
> >> @@ -47,11 +36,31 @@ config USB_DWC2_PCI
> >>  comment "Gadget mode requires USB Gadget support to be enabled"
> >>  
> >>  config USB_DWC2_PERIPHERAL
> >> -	tristate "Gadget only mode"
> >> -	depends on USB_GADGET
> >> +	bool "Gadget only mode"
> >> +	depends on USB_GADGET=y || USB_GADGET=USB_DWC2
> >>  	help
> >>  	  The Designware USB2.0 high-speed gadget controller
> >> -	  integrated into many SoCs.
> >> +	  integrated into many SoCs. Select this option if you want the
> >> +	  driver to operate in Peripheral-only mode. This option requires
> >> +	  USB_GADGET=y.
> >> +
> >> +config USB_DWC2_DUAL_ROLE
> >> +	bool "Dual Role mode"
> >> +	depends on ((USB=y || USB=USB_DWC2) && (USB_GADGET=y || USB_GADGET=USB_DWC2))
> > 
> > I believe that extra parentheses are not needed.
> 
> Yes, I can remove the extra parentheses.
> 
> > 
> >> +	help
> >> +	  Select this option if you want the driver to work in a dual-role
> >> +	  mode. In this mode both host and gadget features are enabled, and
> >> +	  the role will be determined by the cable that gets plugged-in. This
> >> +	  option requires USB_GADGET=y.
> >> +endchoice
> >> +
> >> +config USB_DWC2_PLATFORM
> >> +	bool
> >> +        depends on !PCI
> > 
> > Why have you introduced this limitation (without even mentioning it in
> > the patch description)?  I suspect that by this change and disabling
> > PCI in your config you've workarounded the issue of having the common
> > module for PCI and platform parts completely.  Sorry but this is
> > incorrect as we want to have PCI and platform support in one compiled
> > kernel.
> 
> Yes...I will remove.
> 
> > 
> >> +        default y
> >> +        help
> >> +          The Designware USB2.0 platform interface module for
> >> +          controllers directly connected to the CPU.
> >>  
> >>  config USB_DWC2_DEBUG
> >>  	bool "Enable Debugging Messages"
> >> diff --git a/drivers/usb/dwc2/Makefile b/drivers/usb/dwc2/Makefile
> >> index b73d2a5..3026135 100644
> >> --- a/drivers/usb/dwc2/Makefile
> >> +++ b/drivers/usb/dwc2/Makefile
> >> @@ -1,10 +1,17 @@
> >>  ccflags-$(CONFIG_USB_DWC2_DEBUG)	+= -DDEBUG
> >>  ccflags-$(CONFIG_USB_DWC2_VERBOSE)	+= -DVERBOSE_DEBUG
> >>  
> >> -obj-$(CONFIG_USB_DWC2_HOST)		+= dwc2.o
> >> +obj-$(CONFIG_USB_DWC2)			+= dwc2.o
> >>  dwc2-y					:= core.o core_intr.o
> >> -dwc2-y					+= hcd.o hcd_intr.o
> >> -dwc2-y					+= hcd_queue.o hcd_ddma.o
> >> +
> >> +ifneq ($(filter y,$(CONFIG_USB_DWC2_HOST) $(CONFIG_USB_DWC2_DUAL_ROLE)),)
> >> +	dwc2-y				+= hcd.o hcd_intr.o
> >> +	dwc2-y				+= hcd_queue.o hcd_ddma.o
> >> +endif
> >> +
> >> +ifneq ($(filter y,$(CONFIG_USB_DWC2_PERIPHERAL) $(CONFIG_USB_DWC2_DUAL_ROLE)),)
> >> +	dwc2-y       			+= gadget.o
> >> +endif
> >>  
> >>  # NOTE: The previous s3c-hsotg peripheral mode only driver has been moved to
> >>  # this location and renamed gadget.c. When building for dynamically linked
> > 
> > This comment is no longer true after your changes.
> 
> Well, this patch series doesn't affect this comment. gadget.c is still
> gadget.c that was renamed from s3c-hsotg. I'd like to leave this comment
> here for now because people are still forgetting that s3c-hsotg is now
> gadget.

I was referring to the full comment (in the patch there are only two first
lines shown):

# NOTE: The previous s3c-hsotg peripheral mode only driver has been moved to
# this location and renamed gadget.c. When building for dynamically linked
# modules, dwc2_gadget.ko will get built for peripheral mode. For host mode,
# the core module will be dwc2.ko, the PCI bus interface module will called
# dwc2_pci.ko and the platform interface module will be called dwc2_platform.ko.
# At present the host and gadget driver will be separate drivers, but there
# are plans in the near future to create a dual-role driver.

> > 
> >> @@ -19,10 +26,4 @@ ifneq ($(CONFIG_USB_DWC2_PCI),)
> >>  	dwc2_pci-y			:= pci.o
> >>  endif
> > 
> > dwc2_pci will still be build as separate module despite what the updated
> > documentation for USB_DWC2 says.
> 
> Ah...So should I keep for PCD, dwc2-pci.ko or dwc2.ko?
> 
> > 
> >> -ifneq ($(CONFIG_USB_DWC2_PLATFORM),)
> >> -	obj-$(CONFIG_USB_DWC2_HOST)	+= dwc2_platform.o
> >> -	dwc2_platform-y			:= platform.o
> >> -endif
> >> -
> >> -obj-$(CONFIG_USB_DWC2_PERIPHERAL)	+= dwc2_gadget.o
> >> -dwc2_gadget-y				:= gadget.o
> >> +dwc2-$(CONFIG_USB_DWC2_PLATFORM) += platform.o
> > 
> > platform.c references code from hcd.c but will be built alone for
> > USB_DWC2_PERIPHERAL=y config (the link failure will happen).
> 
> I believed I have wrapped all the necessary functions from hcd.c so that
> the link failure will not happen. But I will check again.

Using socfpage_defconfig and USB_DWC2_PERIPHERAL=y:

  LD      init/built-in.o
drivers/built-in.o: In function `dwc2_hc_set_even_odd_frame':
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/core.c:1230: undefined reference to `dwc2_hcd_get_frame_number'
drivers/built-in.o: In function `dwc2_handle_otg_intr':
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/core_intr.c:211: undefined reference to `dwc2_hcd_start'
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/core_intr.c:248: undefined reference to `dwc2_hcd_start'
drivers/built-in.o: In function `dwc2_handle_usb_suspend_intr':
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/core_intr.c:406: undefined reference to `dwc2_hcd_start'
drivers/built-in.o: In function `dwc2_handle_otg_intr':
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/core_intr.c:239: undefined reference to `dwc2_hcd_disconnect'
drivers/built-in.o: In function `dwc2_driver_remove':
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/platform.c:123: undefined reference to `dwc2_hcd_remove'
drivers/built-in.o: In function `dwc2_driver_probe':
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/platform.c:208: undefined reference to `dwc2_hcd_init'
/home/bzolnier/sam/linux-sprc/drivers/usb/dwc2/platform.c:167: undefined reference to `dwc2_set_all_params'
make: *** [vmlinux] Error 1

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

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