linux-kernel - Re: [PATCH v9 3/3] add support for DWC UFS Host Controller

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Date:	Thu, 03 Mar 2016 13:04:40 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Joao Pinto <Joao.Pinto@...opsys.com>
Cc:	vinholikatti@...il.com, julian.calaby@...il.com,
	akinobu.mita@...il.com, hch@...radead.org, mark.rutland@....com,
	robh@...nel.org, gbroner@...eaurora.org, subhashj@...eaurora.org,
	CARLOS.PALMINHA@...opsys.com, ijc+devicetree@...lion.org.uk,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v9 3/3] add support for DWC UFS Host Controller

On Thursday 03 March 2016 11:39:05 Joao Pinto wrote:
> Hi Arnd,
> 
> On 3/2/2016 7:55 PM, Arnd Bergmann wrote:
> > On Wednesday 02 March 2016 16:46:47 Joao Pinto wrote:
> >> On 2/19/2016 3:03 PM, Arnd Bergmann wrote:
> >>> On Thursday 18 February 2016 17:20:27 Joao Pinto wrote:
> 
> Facts:
> 
> - Test Chip type are currently not detectable in runtime through the controller
> - In the future the Test Chip version will be available in the controller
> - Test Chip initialization is different for each type
> - The IP Core version is 1.40a
> - Test Chip version is 6.00
> - Teh UFS version is 2.0

Ok.

> Suggested driver architecture:
> 
> Platform setup:
>  tc-dwc-g210-pltfrm --> tc-dwc-g210 --> ufshcd-dwc-pltfrm --> ufshcd-dwc --> ufs
> 
> The test chip platform driver could be called through 2 compatibility strings.
> indicating the chip's version and bit type:
>  "snps, g210-tc-6.00-20bit"
>  "snps, g210-tc-6.00-40bit"

Yes, this sounds good. We can probably skip one of the middle layers,
but basically that is what I was looking for.

> The device tree node would have additional info compatibility strings as the DWC
> IP core version and UFS version:
>  "snps, dwc-ufshcd-1.40a"
>  "jedec, ufs-2.0"
> 
> PCI based setup:
>  tc-dwc-g210-pci --> tc-dwc-g210 --> ufshcd-dwc-pci --> ufshcd-dwc --> ufs

The tc-dwc-g210 portion probably shouldn't depend on both
ufshcd-dwc-pltfrm and ufshcd-dwc-pci here, so how about leaving
those two out?


Then it becomes

   tc-dwc-g210-pci ---> tc-dwc-g210 --> ufshcd-dwc --> ufs
tc-dwc-g210-pltfrm --/

> The test chip type would be configured by a parameter to be passed in the kernel
> boot args: tc_type = 20 (20-bit) or tc_type = 40 (40-bit)

Right. With module_param() helper, this will be either a boot command
line option, or a module load option, depending on whether the driver
is built-on or not.

modprobe tc-dwc-g210-pci tc_type=20

command line: tc-dwc-g210-pci.tc_type=20
 
> Having this in mind the KConfig would be:
> 
> "config SCSI_UFS_DWC_HOOKS
> 	bool

I think we can now remove the config option for the hooks as well.

> config SCSI_UFS_DWC_PLAT
> 	tristate "DesignWare UFS controller platform glue driver"
> 	depends on SCSI_UFSHCD_PLATFORM
> 	select SCSI_UFS_DWC_HOOKS
> 	help
> 	  This selects the DesignWare UFS host controller platform glue driver.
> 
> 	  Select this if you have a DesignWare UFS controller on Platform bus.
> 	  If unsure, say N.
> 
> config SCSI_UFS_DWC_PCI
> 	tristate "DesignWare UFS controller pci glue driver"
> 	depends on SCSI_UFSHCD_PCI
> 	select SCSI_UFS_DWC_HOOKS
> 	help
> 	  This selects the DesignWare UFS host controller pci glue driver.
> 
> 	  Select this if you have a DesignWare UFS controller on pci bus.
> 	  If unsure, say N.
> 
> config SCSI_UFS_DWC_TC
> 	bool "Support for the Synopsys Test Chip"
> 	depends on SCSI_UFS_DWC_HOOKS && (SCSI_UFSHCD_PCI || SCSI_UFS_DWC_PLAT)
> 	---help---
> 	  Synopsys Test Chip is a Phy for prototyping purposes.
> 	  This selects the support for the Synopsys Test Chip.
> 
> 	  Select this if you have a Synopsys Test Chip.
> 	  If unsure, say N."
> 
> Agree with the approach?

This would work, but I think it's better to define the options in terms
of the top-level drivers, i.e. SCSI_UFS_DWC_TC_PCI and SCSI_UFS_DWC_TC_PLATFORM,
and then make the other options hidden and implicitly turned out by them.

	Arnd