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From:   Stanislav Nijnikov <Stanislav.Nijnikov@wdc.com>
To:     Evan Green <evgreen@chromium.org>,
        Vinayak Holikatti <vinholikatti@gmail.com>,
        "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        Bart Van Assche <Bart.VanAssche@wdc.com>
Subject: RE: [PATCH v3] scsi: ufs: Make sysfs attributes writable
Thread-Topic: [PATCH v3] scsi: ufs: Make sysfs attributes writable
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Date:   Mon, 6 Aug 2018 09:28:26 +0000
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Hi Evan,

> -----Original Message-----
> From: Evan Green <evgreen@chromium.org>
> Sent: Wednesday, July 25, 2018 11:15 PM
> To: Vinayak Holikatti <vinholikatti@gmail.com>; James E.J. Bottomley <jej=
b@linux.vnet.ibm.com>; Martin K. Petersen
> <martin.petersen@oracle.com>; Stanislav Nijnikov <Stanislav.Nijnikov@wdc.=
com>; Adrian Hunter <adrian.hunter@intel.com>; linux-
> kernel@vger.kernel.org; linux-scsi@vger.kernel.org; Bart Van Assche <Bart=
.VanAssche@wdc.com>
> Cc: Evan Green <evgreen@chromium.org>
> Subject: [PATCH v3] scsi: ufs: Make sysfs attributes writable
>=20
> This change makes the UFS controller's sysfs attributes writable, which
> will enable users to modify attributes. This can be useful during factory
> provisioning for setting up critical attributes like the reference clock
> frequency.
>=20
> Signed-off-by: Evan Green <evgreen@chromium.org>
> ---
> Configfs was determined to be the preferred mechanism for writing the
> config descriptor, but attributes also need to be written during setup,
> and are already present in sysfs. Making these attributes writable is
> also helpful for debugging and experimentation.
>=20
> Changes since v2:
> 	- Removed the configuration descriptor changes from the series,
> since configfs was the preferred way to write to that, leaving only
> this change.
>=20
> Changes since v1:
> 	- Reworked the interface to show each unit of the config
> descriptor as a separate directory, rather than the previous method I
> had of a file for selecting the unit, and then a common set of files
> that interacted with whichever unit was selected. I did some kobject
> magic to accomplish this. I noticed from Greg KH's reply to Sayali's
> patches [1] that configfs might be the preferred method. Let me know
> if I should abandon this series in favor of Sayali's, with the
> possible exception of "Make sysfs attributes writable".
> 	- Squashed documentation changes into their respective code
> changes.
> 	- I decided to keep the config descriptor attributes as their
> own files, rather than hiding writes behind device descriptor and unit
> descriptor, as I think that's more future proof and true to the UFS spec.
>=20
> [1] https://lkml.org/lkml/2018/6/8/210
>=20
>  Documentation/ABI/testing/sysfs-driver-ufs | 17 +--------
>  drivers/scsi/ufs/ufs-sysfs.c               | 58 ++++++++++++++++++++----=
------
>  2 files changed, 40 insertions(+), 35 deletions(-)
>=20
> diff --git a/Documentation/ABI/testing/sysfs-driver-ufs b/Documentation/A=
BI/testing/sysfs-driver-ufs
> index 016724ec26d5..44f3b9691e59 100644
> --- a/Documentation/ABI/testing/sysfs-driver-ufs
> +++ b/Documentation/ABI/testing/sysfs-driver-ufs
> @@ -685,7 +685,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the boot lun enabled UFS device attribut=
e.
>  		The full information about the attribute could be found at
>  		UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/current_power_mode
>  Date:		February 2018
> @@ -693,7 +692,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the current power mode UFS device attrib=
ute.
>  		The full information about the attribute could be found at
>  		UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/active_icc_level
>  Date:		February 2018
> @@ -701,7 +699,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the active icc level UFS device attribut=
e.
>  		The full information about the attribute could be found at
>  		UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/ooo_data_enabled
>  Date:		February 2018
> @@ -709,7 +706,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the out of order data transfer enabled U=
FS
>  		device attribute. The full information about the attribute
>  		could be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/bkops_status
>  Date:		February 2018
> @@ -717,7 +713,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the background operations status UFS dev=
ice
>  		attribute. The full information about the attribute could
>  		be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/purge_status
>  Date:		February 2018
> @@ -725,7 +720,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the purge operation status UFS device
>  		attribute. The full information about the attribute could
>  		be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/max_data_in_size
>  Date:		February 2018
> @@ -733,7 +727,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file shows the maximum data size in a DATA IN
>  		UPIU. The full information about the attribute could
>  		be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/max_data_out_size
>  Date:		February 2018
> @@ -741,7 +734,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file shows the maximum number of bytes that can be
>  		requested with a READY TO TRANSFER UPIU. The full information
>  		about the attribute could be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/reference_clock_fre=
quency
>  Date:		February 2018
> @@ -749,14 +741,13 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc=
.com>
>  Description:	This file provides the reference clock frequency UFS device
>  		attribute. The full information about the attribute could
>  		be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/configuration_descr=
iptor_lock
>  Date:		February 2018
>  Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.com>
>  Description:	This file shows whether the configuration descriptor is loc=
ked.
>  		The full information about the attribute could be found at
> -		UFS specifications 2.1. The file is read only.
> +		UFS specifications 2.1.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/max_number_of_rtt
>  Date:		February 2018
> @@ -765,7 +756,6 @@ Description:	This file provides the maximum current n=
umber of
>  		outstanding RTTs in device that is allowed. The full
>  		information about the attribute could be found at
>  		UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/exception_event_con=
trol
>  Date:		February 2018
> @@ -773,7 +763,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the exception event control UFS device
>  		attribute. The full information about the attribute could
>  		be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/exception_event_sta=
tus
>  Date:		February 2018
> @@ -781,7 +770,6 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.c=
om>
>  Description:	This file provides the exception event status UFS device
>  		attribute. The full information about the attribute could
>  		be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/ffu_status
>  Date:		February 2018
> @@ -789,14 +777,12 @@ Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc=
.com>
>  Description:	This file provides the ffu status UFS device attribute.
>  		The full information about the attribute could be found at
>  		UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/psa_state
>  Date:		February 2018
>  Contact:	Stanislav Nijnikov <stanislav.nijnikov@wdc.com>
>  Description:	This file show the PSA feature status. The full information
>  		about the attribute could be found at UFS specifications 2.1.
> -		The file is read only.
>=20
>  What:		/sys/bus/platform/drivers/ufshcd/*/attributes/psa_data_size
>  Date:		February 2018
> @@ -805,7 +791,6 @@ Description:	This file shows the amount of data that =
the host plans to
>  		load to all logical units in pre-soldering state.
>  		The full information about the attribute could be found at
>  		UFS specifications 2.1.
> -		The file is read only.
>=20
>=20
>  What:		/sys/class/scsi_device/*/device/dyn_cap_needed
> diff --git a/drivers/scsi/ufs/ufs-sysfs.c b/drivers/scsi/ufs/ufs-sysfs.c
> index 8d9332bb7d0c..5e286b9d1aea 100644
> --- a/drivers/scsi/ufs/ufs-sysfs.c
> +++ b/drivers/scsi/ufs/ufs-sysfs.c
> @@ -655,7 +655,7 @@ static const struct attribute_group ufs_sysfs_flags_g=
roup =3D {
>  	.attrs =3D ufs_sysfs_device_flags,
>  };
>=20
> -#define UFS_ATTRIBUTE(_name, _uname)					\
> +#define UFS_ATTRIBUTE_SHOW(_name, _uname)				\
>  static ssize_t _name##_show(struct device *dev,				\
>  	struct device_attribute *attr, char *buf)			\
>  {									\
> @@ -665,25 +665,45 @@ static ssize_t _name##_show(struct device *dev,				=
\
>  		QUERY_ATTR_IDN##_uname, 0, 0, &value))			\
>  		return -EINVAL;						\
>  	return sprintf(buf, "0x%08X\n", value);				\
> -}									\
> -static DEVICE_ATTR_RO(_name)
> +}
>=20
> -UFS_ATTRIBUTE(boot_lun_enabled, _BOOT_LU_EN);
> -UFS_ATTRIBUTE(current_power_mode, _POWER_MODE);
> -UFS_ATTRIBUTE(active_icc_level, _ACTIVE_ICC_LVL);
> -UFS_ATTRIBUTE(ooo_data_enabled, _OOO_DATA_EN);
> -UFS_ATTRIBUTE(bkops_status, _BKOPS_STATUS);
> -UFS_ATTRIBUTE(purge_status, _PURGE_STATUS);
> -UFS_ATTRIBUTE(max_data_in_size, _MAX_DATA_IN);
> -UFS_ATTRIBUTE(max_data_out_size, _MAX_DATA_OUT);
> -UFS_ATTRIBUTE(reference_clock_frequency, _REF_CLK_FREQ);
> -UFS_ATTRIBUTE(configuration_descriptor_lock, _CONF_DESC_LOCK);
> -UFS_ATTRIBUTE(max_number_of_rtt, _MAX_NUM_OF_RTT);
> -UFS_ATTRIBUTE(exception_event_control, _EE_CONTROL);
> -UFS_ATTRIBUTE(exception_event_status, _EE_STATUS);
> -UFS_ATTRIBUTE(ffu_status, _FFU_STATUS);
> -UFS_ATTRIBUTE(psa_state, _PSA_STATE);
> -UFS_ATTRIBUTE(psa_data_size, _PSA_DATA_SIZE);
> +#define UFS_ATTRIBUTE_RO(_name, _uname)					\
> +UFS_ATTRIBUTE_SHOW(_name, _uname)					\
> +DEVICE_ATTR_RO(_name)
It should be static here.

> +
> +#define UFS_ATTRIBUTE_RW(_name, _uname)					\
> +UFS_ATTRIBUTE_SHOW(_name, _uname)					\
> +static ssize_t _name##_store(struct device *dev,			\
> +		struct device_attribute *attr, const char *buf,		\
> +		size_t count)						\
> +{									\
> +	struct ufs_hba *hba =3D dev_get_drvdata(dev);			\
> +	u32 value;							\
> +	if (kstrtou32(buf, 0, &value))					\
> +		return -EINVAL;						\
> +	if (ufshcd_query_attr(hba, UPIU_QUERY_OPCODE_WRITE_ATTR,	\
> +		QUERY_ATTR_IDN##_uname, 0, 0, &value))			\
> +		return -EINVAL;						\
> +	return count;							\
> +}									\
> +static DEVICE_ATTR_RW(_name)
> +
> +UFS_ATTRIBUTE_RW(boot_lun_enabled, _BOOT_LU_EN);
> +UFS_ATTRIBUTE_RO(current_power_mode, _POWER_MODE);
> +UFS_ATTRIBUTE_RW(active_icc_level, _ACTIVE_ICC_LVL);
> +UFS_ATTRIBUTE_RW(ooo_data_enabled, _OOO_DATA_EN);
I would prefer to leave "write once" attributes as read-only.

> +UFS_ATTRIBUTE_RO(bkops_status, _BKOPS_STATUS);
> +UFS_ATTRIBUTE_RO(purge_status, _PURGE_STATUS);
> +UFS_ATTRIBUTE_RW(max_data_in_size, _MAX_DATA_IN);
> +UFS_ATTRIBUTE_RW(max_data_out_size, _MAX_DATA_OUT);
> +UFS_ATTRIBUTE_RW(reference_clock_frequency, _REF_CLK_FREQ);
> +UFS_ATTRIBUTE_RW(configuration_descriptor_lock, _CONF_DESC_LOCK);
Same here, "write once" attribute.

> +UFS_ATTRIBUTE_RW(max_number_of_rtt, _MAX_NUM_OF_RTT);
> +UFS_ATTRIBUTE_RW(exception_event_control, _EE_CONTROL);
> +UFS_ATTRIBUTE_RW(exception_event_status, _EE_STATUS);
This one is read only attribute.

> +UFS_ATTRIBUTE_RO(ffu_status, _FFU_STATUS);
> +UFS_ATTRIBUTE_RO(psa_state, _PSA_STATE);
> +UFS_ATTRIBUTE_RO(psa_data_size, _PSA_DATA_SIZE);
>=20
>  static struct attribute *ufs_sysfs_attributes[] =3D {
>  	&dev_attr_boot_lun_enabled.attr,
> --
> 2.16.4

I would add some write option to some flags as well. For example, enabling/
disabling the background operations could be very useful.

Regards
Stanislav