[v3,2/2] scsi: ufs: Add HCI capabilities sysfs group

The standard register map of UFSHCI is comprised of several groups.  The
first group (starting from offset 0x00), is the host capabilities group.
It contains some interesting information, that otherwise is not
available, e.g. the UFS version of the platform etc.

Reviewed-by: Keoseong Park <keosung.park@samsung.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Avri Altman <avri.altman@wdc.com>
---
 Documentation/ABI/testing/sysfs-driver-ufs | 42 ++++++++++
 drivers/ufs/core/ufs-sysfs.c               | 95 ++++++++++++++++++++++
 2 files changed, 137 insertions(+)

On Fri, 2024-08-09 at 10:23 +0300, Avri Altman wrote:
> The standard register map of UFSHCI is comprised of several groups. 
> The
> first group (starting from offset 0x00), is the host capabilities
> group.
> It contains some interesting information, that otherwise is not
> available, e.g. the UFS version of the platform etc.
> 
> Reviewed-by: Keoseong Park <keosung.park@samsung.com>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> Signed-off-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>

> On Fri, Aug 09, 2024 at 10:23:31AM +0300, Avri Altman wrote:
> > The standard register map of UFSHCI is comprised of several groups.
> > The first group (starting from offset 0x00), is the host capabilities group.
> > It contains some interesting information, that otherwise is not
> > available, e.g. the UFS version of the platform etc.
> >
> > Reviewed-by: Keoseong Park <keosung.park@samsung.com>
> > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> > Signed-off-by: Avri Altman <avri.altman@wdc.com>
> > ---
> >  Documentation/ABI/testing/sysfs-driver-ufs | 42 ++++++++++
> >  drivers/ufs/core/ufs-sysfs.c               | 95 ++++++++++++++++++++++
> >  2 files changed, 137 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-driver-ufs
> > b/Documentation/ABI/testing/sysfs-driver-ufs
> > index fe943ce76c60..b6e0c3b806fd 100644
> > --- a/Documentation/ABI/testing/sysfs-driver-ufs
> > +++ b/Documentation/ABI/testing/sysfs-driver-ufs
> > @@ -1532,3 +1532,45 @@ Contact:       Bean Huo <beanhuo@micron.com>
> >  Description:
> >               rtc_update_ms indicates how often the host should synchronize or
> update the
> >               UFS RTC. If set to 0, this will disable UFS RTC periodic update.
> > +
> > +What:                /sys/devices/platform/.../ufshci_capabilities/capabilities
> > +Date:                August 2024
> > +Contact:     Avri Altman <avri.altman@wdc.com>
> > +Description:
> > +             Host Capabilities register group: host controller capabilities register.
> > +             Symbol - CAP.  Offset: 0x00 - 0x03.
> 
> This doesn't look like an ABI description. You are merely specifying the register
> name and offset that gets accessed while reading this attribute.
> 
> Also, I'm not sure if we really want to expose HCI/MCQ capabilities as sysfs ABI.
Why not?
Like the cover letter say, this info is otherwise unavailable.

> This just prints the hex value without even telling users how to interpret it.
Each register typically carries several parts of info encoded withing its 32 bits.
I am not sure that copying the spec into the documentation is useful.

> 
> > +
> > +What:                /sys/devices/platform/.../ufshci_capabilities/mcq_cap
> > +Date:                August 2024
> > +Contact:     Avri Altman <avri.altman@wdc.com>
> > +Description:
> > +             Host Capabilities register group: multi-circular queue capability
> register.
> > +             Symbol - MCQCAP.  Offset: 0x04 - 0x07.
> > +
> > +What:                /sys/devices/platform/.../ufshci_capabilities/version
> > +Date:                August 2024
> > +Contact:     Avri Altman <avri.altman@wdc.com>
> > +Description:
> > +             Host Capabilities register group: UFS version register.
> > +             Symbol - VER.  Offset: 0x08 - 0x0B.
> 
> This and below attributes are fine.
Still fail to see the difference.

>But the description should be changed. No
> need to put register name and offset here, that is not relevant to the ABI.
> Description should clearly state what is the purpose of the attribute, how to
> interpret (if necessary) and read/write capability. Like,
> 
> ```
>         This file shows the UFSHCD version.
> 
>         The file is read only.
> ```
> 
> Applies to other attributes below.
OK.  Thanks.

Avri

> 
> - Mani
> 
> > +
> > +What:                /sys/devices/platform/.../ufshci_capabilities/ext_capabilities
> > +Date:                August 2024
> > +Contact:     Avri Altman <avri.altman@wdc.com>
> > +Description:
> > +             Host Capabilities register group: extended controller capabilities
> register.
> > +             Symbol - EXT_CAP.  Offset: 0x0C - 0x0F.
> > +
> > +What:                /sys/devices/platform/.../ufshci_capabilities/product_id
> > +Date:                August 2024
> > +Contact:     Avri Altman <avri.altman@wdc.com>
> > +Description:
> > +             Host Capabilities register group: product ID register.
> > +             Symbol - HCPID.  Offset: 0x10 - 0x13.
> > +
> > +What:                /sys/devices/platform/.../ufshci_capabilities/man_id
> > +Date:                August 2024
> > +Contact:     Avri Altman <avri.altman@wdc.com>
> > +Description:
> > +             Host Capabilities register group: manufacturer ID register.
> > +             Symbol - HCMID.  Offset: 0x14 - 0x17.
> > diff --git a/drivers/ufs/core/ufs-sysfs.c
> > b/drivers/ufs/core/ufs-sysfs.c index dec7746c98e0..751d5ff406da 100644
> > --- a/drivers/ufs/core/ufs-sysfs.c
> > +++ b/drivers/ufs/core/ufs-sysfs.c
> > @@ -525,6 +525,100 @@ static const struct attribute_group
> ufs_sysfs_capabilities_group = {
> >       .attrs = ufs_sysfs_capabilities_attrs,  };
> >
> > +static ssize_t capabilities_show(struct device *dev,
> > +             struct device_attribute *attr, char *buf) {
> > +     struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +     return sysfs_emit(buf, "0x%x\n", hba->capabilities); }
> > +
> > +static ssize_t mcq_cap_show(struct device *dev,
> > +             struct device_attribute *attr, char *buf) {
> > +     struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +     if (hba->ufs_version < ufshci_version(4, 0))
> > +             return -EOPNOTSUPP;
> > +
> > +     return sysfs_emit(buf, "0x%x\n", hba->mcq_capabilities); }
> > +
> > +static ssize_t version_show(struct device *dev,
> > +             struct device_attribute *attr, char *buf) {
> > +     struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +     return sysfs_emit(buf, "0x%x\n", hba->ufs_version); }
> > +
> > +static ssize_t ext_capabilities_show(struct device *dev,
> > +             struct device_attribute *attr, char *buf) {
> > +     int ret;
> > +     u32 val;
> > +     struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +     if (hba->ufs_version < ufshci_version(4, 0))
> > +             return -EOPNOTSUPP;
> > +
> > +     ret = ufshcd_read_hci_reg(hba, &val,
> REG_EXT_CONTROLLER_CAPABILITIES);
> > +     if (ret)
> > +             return ret;
> > +
> > +     return sysfs_emit(buf, "0x%x\n", val); }
> > +
> > +static ssize_t product_id_show(struct device *dev,
> > +             struct device_attribute *attr, char *buf) {
> > +     int ret;
> > +     u32 val;
> > +     struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +     ret = ufshcd_read_hci_reg(hba, &val, REG_CONTROLLER_PID);
> > +     if (ret)
> > +             return ret;
> > +
> > +     return sysfs_emit(buf, "0x%x\n", val); }
> > +
> > +static ssize_t man_id_show(struct device *dev,
> > +             struct device_attribute *attr, char *buf) {
> > +     int ret;
> > +     u32 val;
> > +     struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +     ret = ufshcd_read_hci_reg(hba, &val, REG_CONTROLLER_MID);
> > +     if (ret)
> > +             return ret;
> > +
> > +     return sysfs_emit(buf, "0x%x\n", val); }
> > +
> > +static DEVICE_ATTR_RO(capabilities);
> > +static DEVICE_ATTR_RO(mcq_cap);
> > +static DEVICE_ATTR_RO(version);
> > +static DEVICE_ATTR_RO(ext_capabilities); static
> > +DEVICE_ATTR_RO(product_id); static DEVICE_ATTR_RO(man_id);
> > +
> > +static struct attribute *ufs_sysfs_ufshci_cap_attrs[] = {
> > +     &dev_attr_capabilities.attr,
> > +     &dev_attr_mcq_cap.attr,
> > +     &dev_attr_version.attr,
> > +     &dev_attr_ext_capabilities.attr,
> > +     &dev_attr_product_id.attr,
> > +     &dev_attr_man_id.attr,
> > +     NULL
> > +};
> > +
> > +static const struct attribute_group ufs_sysfs_ufshci_group = {
> > +     .name = "ufshci_capabilities",
> > +     .attrs = ufs_sysfs_ufshci_cap_attrs, };
> > +
> >  static ssize_t monitor_enable_show(struct device *dev,
> >                                  struct device_attribute *attr, char
> > *buf)  { @@ -1508,6 +1602,7 @@ static const struct attribute_group
> > ufs_sysfs_attributes_group = {  static const struct attribute_group
> > *ufs_sysfs_groups[] = {
> >       &ufs_sysfs_default_group,
> >       &ufs_sysfs_capabilities_group,
> > +     &ufs_sysfs_ufshci_group,
> >       &ufs_sysfs_monitor_group,
> >       &ufs_sysfs_power_info_group,
> >       &ufs_sysfs_device_descriptor_group,
> > --
> > 2.25.1
> >
> >
> 
> --
> மணிவண்ணன் சதாசிவம்

On Sun, Aug 11, 2024 at 06:19:49AM +0000, Avri Altman wrote:
> > On Fri, Aug 09, 2024 at 10:23:31AM +0300, Avri Altman wrote:
> > > The standard register map of UFSHCI is comprised of several groups.
> > > The first group (starting from offset 0x00), is the host capabilities group.
> > > It contains some interesting information, that otherwise is not
> > > available, e.g. the UFS version of the platform etc.
> > >
> > > Reviewed-by: Keoseong Park <keosung.park@samsung.com>
> > > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> > > Signed-off-by: Avri Altman <avri.altman@wdc.com>
> > > ---
> > >  Documentation/ABI/testing/sysfs-driver-ufs | 42 ++++++++++
> > >  drivers/ufs/core/ufs-sysfs.c               | 95 ++++++++++++++++++++++
> > >  2 files changed, 137 insertions(+)
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-driver-ufs
> > > b/Documentation/ABI/testing/sysfs-driver-ufs
> > > index fe943ce76c60..b6e0c3b806fd 100644
> > > --- a/Documentation/ABI/testing/sysfs-driver-ufs
> > > +++ b/Documentation/ABI/testing/sysfs-driver-ufs
> > > @@ -1532,3 +1532,45 @@ Contact:       Bean Huo <beanhuo@micron.com>
> > >  Description:
> > >               rtc_update_ms indicates how often the host should synchronize or
> > update the
> > >               UFS RTC. If set to 0, this will disable UFS RTC periodic update.
> > > +
> > > +What:                /sys/devices/platform/.../ufshci_capabilities/capabilities
> > > +Date:                August 2024
> > > +Contact:     Avri Altman <avri.altman@wdc.com>
> > > +Description:
> > > +             Host Capabilities register group: host controller capabilities register.
> > > +             Symbol - CAP.  Offset: 0x00 - 0x03.
> > 
> > This doesn't look like an ABI description. You are merely specifying the register
> > name and offset that gets accessed while reading this attribute.
> > 
> > Also, I'm not sure if we really want to expose HCI/MCQ capabilities as sysfs ABI.
> Why not?

sysfs is an userspace ABI. The information that is exposed is supposed to be
consumed by the sysadmins/userspace applications.

Looking at the contents of the capabilities, I don't think anyone could
interpret what is being exposed unless they have access to the spec (which is
not free).

> Like the cover letter say, this info is otherwise unavailable.

There are other ways to expose this information too, like debugfs. But what
exactly do you want users to do with it?

- Mani

> On Sun, Aug 11, 2024 at 06:19:49AM +0000, Avri Altman wrote:
> > > On Fri, Aug 09, 2024 at 10:23:31AM +0300, Avri Altman wrote:
> > > > The standard register map of UFSHCI is comprised of several groups.
> > > > The first group (starting from offset 0x00), is the host capabilities group.
> > > > It contains some interesting information, that otherwise is not
> > > > available, e.g. the UFS version of the platform etc.
> > > >
> > > > Reviewed-by: Keoseong Park <keosung.park@samsung.com>
> > > > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> > > > Signed-off-by: Avri Altman <avri.altman@wdc.com>
> > > > ---
> > > >  Documentation/ABI/testing/sysfs-driver-ufs | 42 ++++++++++
> > > >  drivers/ufs/core/ufs-sysfs.c               | 95 ++++++++++++++++++++++
> > > >  2 files changed, 137 insertions(+)
> > > >
> > > > diff --git a/Documentation/ABI/testing/sysfs-driver-ufs
> > > > b/Documentation/ABI/testing/sysfs-driver-ufs
> > > > index fe943ce76c60..b6e0c3b806fd 100644
> > > > --- a/Documentation/ABI/testing/sysfs-driver-ufs
> > > > +++ b/Documentation/ABI/testing/sysfs-driver-ufs
> > > > @@ -1532,3 +1532,45 @@ Contact:       Bean Huo <beanhuo@micron.com>
> > > >  Description:
> > > >               rtc_update_ms indicates how often the host should
> > > > synchronize or
> > > update the
> > > >               UFS RTC. If set to 0, this will disable UFS RTC periodic update.
> > > > +
> > > > +What:                /sys/devices/platform/.../ufshci_capabilities/capabilities
> > > > +Date:                August 2024
> > > > +Contact:     Avri Altman <avri.altman@wdc.com>
> > > > +Description:
> > > > +             Host Capabilities register group: host controller capabilities register.
> > > > +             Symbol - CAP.  Offset: 0x00 - 0x03.
> > >
> > > This doesn't look like an ABI description. You are merely specifying
> > > the register name and offset that gets accessed while reading this attribute.
> > >
> > > Also, I'm not sure if we really want to expose HCI/MCQ capabilities as sysfs
> ABI.
> > Why not?
> 
> sysfs is an userspace ABI. The information that is exposed is supposed to be
> consumed by the sysadmins/userspace applications.
> 
> Looking at the contents of the capabilities, I don't think anyone could interpret
> what is being exposed unless they have access to the spec (which is not free).
> 
> > Like the cover letter say, this info is otherwise unavailable.
> 
> There are other ways to expose this information too, like debugfs. But what
> exactly do you want users to do with it?
OK.  Will drop those.

Thanks,
Avri

> 
> - Mani
> 
> --
> மணிவண்ணன் சதாசிவம்