Message-ID: <56D718F7.9060200@synopsys.com>
Date:	Wed, 2 Mar 2016 16:46:47 +0000
From:	Joao Pinto <Joao.Pinto@...opsys.com>
To:	Arnd Bergmann <arnd@...db.de>, 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


Hi Arnd,

On 2/19/2016 3:03 PM, Arnd Bergmann wrote:
> On Thursday 18 February 2016 17:20:27 Joao Pinto wrote:
>>
>>  Documentation/devicetree/bindings/ufs/ufs-dwc.txt |  19 +
>>  MAINTAINERS                                       |   6 +
>>  drivers/scsi/ufs/Kconfig                          |  51 +++
>>  drivers/scsi/ufs/Makefile                         |   3 +
>>  drivers/scsi/ufs/ufs-dwc-pci.c                    | 172 +++++++++
>>  drivers/scsi/ufs/ufs-dwc.c                        |  96 +++++
>>  drivers/scsi/ufs/ufshcd-dwc.c                     | 431 ++++++++++++++++++++++
>>  drivers/scsi/ufs/ufshcd-dwc.h                     |  18 +
>>  drivers/scsi/ufs/ufshci-dwc.h                     |  42 +++
>>  drivers/scsi/ufs/unipro.h                         |  39 ++
> 
> I still think this can be split up further. From your previous
> explanation, I understand that there is a specific test chip
> that uses the "snps,ufshcd-dwc" implementation along with some
> other glue logic.
> 
> Please split this out so you have anything related to the test
> chips separate from the patch that implements core logic.

Ok, I will split more the patches.

>  
>> diff --git a/Documentation/devicetree/bindings/ufs/ufs-dwc.txt b/Documentation/devicetree/bindings/ufs/ufs-dwc.txt
>> new file mode 100644
>> index 0000000..59e9822
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/ufs/ufs-dwc.txt
>> @@ -0,0 +1,19 @@
>> +* Universal Flash Storage (UFS) DesignWare Host Controller
>> +
>> +DWC_UFSHC nodes are defined to describe on-chip UFS host controllers.
>> +Each UFS controller instance should have its own node.
>> +
>> +Required properties:
>> +- compatible        : compatible list must contain "snps,ufshcd-dwc" and should
>> +		      also contain the JEDEC version of the controller:
>> +			"jedec,ufs-1.1"
>> +			"jedec,ufs-2.0"
>> +- reg               : <registers mapping>
>> +- interrupts        : <interrupt mapping for UFS host controller IRQ>
> 
> 
> Based on your last reply to me (sorry for coming back to this so
> late), I think having just "snps,ufshcd-dwc" as the compatible
> string is not appropriate: This assumes that all "snps,ufshcd-dwc"
> instances are 100% compatible, but your code makes it very clear
> that this is not the case.
> 
> Please for the last time (!) add a proper version number of the
> specific IP block to the compatible strings so you can identify
> what hardware you are talking to.
> 
> You earlier confused the version number of the UFS standard with
> the version number of the controller, and that has been clarified
> now, but you really still need to use a version for the hardware
> as well.

Ok, we can have a "snps,ufshcd-dwc-1.1" and a "snps,ufshcd-dwc-2.0". Agree?

> 
>> +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.
>> +
>> +config SCSI_UFS_DWC_20BIT_RMMI
>> +	bool "20-bit RMMI support"
>> +	depends on SCSI_UFS_DWC_TC
>> +	---help---
>> +	  This specifies that the Synopsys Test Chip supports 20-bit RMMI.
>> +
>> +	  Select this if you are using a 20-bit RMMI Synopsys Test Chip.
>> +	  If unsure, say N.
>> +
>> +config SCSI_UFS_DWC_40BIT_RMMI
>> +	bool "40-bit RMMI support"
>> +	depends on SCSI_UFS_DWC_TC
>> +	---help---
>> +	  Synopsys Test Chip is a Phy for prototyping purposes.
>> +
>> +	  Select this if you are using a 40-bit RMMI Synopsys Test Chip.
>> +	  If unsure, say N.
> 
> I think it would be better to remove the SCSI_UFS_DWC_20BIT_RMMI
> and SCSI_UFS_DWC_40BIT_RMMI configuration options now, and always
> support both. There is not really much need for the options
> as this is just a test chip, and nobody is going to care much
> about saving a few bytes of object code.

We need to know if we are dealing with a 20-bit test chip or a 40-bit test chip
because the initialization is different. That can be made in the device tree as
you say bellow, but we can also use a setup in which the host is a PC (so no
device tree) connected by pci bus to an fpga containing the UFS controller.
Having this, I think that the only way is to choose the 20/40bit stuff in the
menuconfig.

> 
>> diff --git a/drivers/scsi/ufs/Makefile b/drivers/scsi/ufs/Makefile
>> index 8303bcc..bab8c05 100644
>> --- a/drivers/scsi/ufs/Makefile
>> +++ b/drivers/scsi/ufs/Makefile
>> @@ -1,4 +1,7 @@
>>  # UFSHCD makefile
>> +obj-$(CONFIG_SCSI_UFS_DWC_HOOKS) += ufshcd-dwc.o
>> +obj-$(CONFIG_SCSI_UFS_DWC_PLAT) += ufs-dwc.o
>> +obj-$(CONFIG_SCSI_UFS_DWC_PCI) += ufs-dwc-pci.o
>>  obj-$(CONFIG_SCSI_UFS_QCOM) += ufs-qcom.o
>>  obj-$(CONFIG_SCSI_UFSHCD) += ufshcd.o
>>  obj-$(CONFIG_SCSI_UFSHCD_PCI) += ufshcd-pci.o
> 
> However, please split out the SCSI_UFS_DWC_TC specific bits into
> a separate file, and put the module_platform_driver() bits into
> that file, to get the right abstraction where the most specific
> driver calls into the next driver, like
> 
> dwc-test-chip -> dwc-platform -> dwc -> ufs

I think that it is a good idea and we isolate the test chip logic. If in the
future anyone uses DWC core with a real PHY then they can have a phy driver
calling dwc-platform. Agree?

> 
> It's possible you can leave out the dwc-platform level here, as there
> are no other users for now, we can add others later as needed.
> 
>> +/**
>> + * ufshcd_dwc_setup_tc()
>> + * This function configures Local (host) Synopsys TC specific attributes
>> + *
>> + * @hba: Pointer to drivers structure
>> + *
>> + * Returns 0 on success non-zero value on failure
>> + */
>> +static int ufshcd_dwc_setup_tc(struct ufs_hba *hba)
>> +{
>> +	int ret = 0;
>> +
>> +#ifdef CONFIG_SCSI_UFS_DWC_40BIT_RMMI
>> +	dev_info(hba->dev, "Configuring Test Chip 40-bit RMMI\n");
>> +	ret = ufshcd_dwc_setup_40bit_rmmi(hba);
>> +	if (ret) {
>> +		dev_err(hba->dev, "Configuration failed\n");
>> +		goto out;
>> +	}
>> +#endif
>> +
>> +#ifdef CONFIG_SCSI_UFS_DWC_20BIT_RMMI
>> +	dev_info(hba->dev, "Configuring Test Chip 20-bit RMMI\n");
>> +	ret = ufshcd_dwc_setup_20bit_rmmi(hba);
>> +	if (ret) {
>> +		dev_err(hba->dev, "Configuration failed\n");
>> +		goto out;
>> +	}
>> +#endif
> 
> You have changed the #if/#else into two #if sections, but this
> still seems broken when both are enabled, it just cannot work
> unless you have some runtime detection in place.
> 

Please check my comments upstream.

> Depending on whether this is actually the same hardware with
> different settings, or different variants of the test chip,
> please use either a boolean DT property to determine which
> one you need, or use a separate "compatible" string in DT
> for each version of the test chip.

As I say upstream, we can have a setup with the kernel running in a PC connected
to the UFS controller by PCI, so the DT scenario is no good.

> 
>> +/**
>> + * ufshcd_dwc_link_startup_notify()
>> + * UFS Host DWC specific link startup sequence
>> + * @hba: private structure poitner
>> + * @status: Callback notify status
>> + *
>> + * Returns 0 on success, non-zero value on failure
>> + */
>> +int ufshcd_dwc_link_startup_notify(struct ufs_hba *hba,
>> +					enum ufs_notify_change_status status)
>> +{
>> +	int err = 0;
>> +
>> +	if (status == PRE_CHANGE) {
>> +		ufshcd_dwc_program_clk_div(hba, DWC_UFS_REG_HCLKDIV_DIV_125);
>> +#ifdef CONFIG_SCSI_UFS_DWC_TC
>> +		err = ufshcd_dwc_setup_tc(hba);
>> +		if (err) {
>> +			dev_err(hba->dev, "Configuration failed (%d)\n",
>> +									err);
>> +			goto out;
>> +		}
>> +#endif
>> +	} else { /* POST_CHANGE */
> 
> Similar, this #ifdef should almost certainly be rewritten so that
> only a DT that identifies as the test chip will call that.

The same.

> 
> 	Arnd
> 

Joao

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