ice: check netlist before enabling ICE_F_GNSS

Similar to the change made for ICE_F_SMA_CTRL, check the netlist before
enabling support for ICE_F_GNSS. This ensures that the driver only enables
the GNSS feature on devices which actually have the feature enabled in the
firmware device configuration.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: Don't dereference NULL in ice_gnss_read error path

If pf is NULL in ice_gnss_read() then it will be dereferenced
in the error path by a call to dev_dbg(ice_pf_to_dev(pf), ...).

Avoid this by simply returning in this case.
If logging is desired an alternate approach might be to
use pr_err() before returning.

Flagged by Smatch as:

.../ice_gnss.c:196 ice_gnss_read() error: we previously assumed 'pf' could be null (see line 131)

Fixes: 43113ff73453 ("ice: add TTY for GNSS module for E810T device")
Signed-off-by: Simon Horman <horms@kernel.org>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: make writes to /dev/gnssX synchronous

The current ice driver's GNSS write implementation buffers writes and
works through them asynchronously in a kthread. That's bad because:
- The GNSS write_raw operation is supposed to be synchronous[1][2].
- There is no upper bound on the number of pending writes.
Userspace can submit writes much faster than the driver can process,
consuming unlimited amounts of kernel memory.

A patch that's currently on review[3] ("[v3,net] ice: Write all GNSS
buffers instead of first one") would add one more problem:
- The possibility of waiting for a very long time to flush the write
work when doing rmmod, softlockups.

To fix these issues, simplify the implementation: Drop the buffering,
the write_work, and make the writes synchronous.

I tested this with gpsd and ubxtool.

[1] https://events19.linuxfoundation.org/wp-content/uploads/2017/12/The-GNSS-Subsystem-Johan-Hovold-Hovold-Consulting-AB.pdf
"User interface" slide.
[2] A comment in drivers/gnss/core.c:gnss_write():
/* Ignoring O_NONBLOCK, write_raw() is synchronous. */
[3] https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20230217120541.16745-1-karol.kolacinski@intel.com/

Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

ice: do not busy-wait to read GNSS data

The ice-gnss-<dev_name> kernel thread, which reads data from the u-blox
GNSS module, keep a CPU core almost 100% busy. The main reason is that
it busy-waits for data to become available.

A simple improvement would be to replace the "mdelay(10);" in
ice_gnss_read() with sleeping. A better fix is to not do any waiting
directly in the function and just requeue this delayed work as needed.
The advantage is that canceling the work from ice_gnss_exit() becomes
immediate, rather than taking up to ~2.5 seconds (ICE_MAX_UBX_READ_TRIES
* 10 ms).

This lowers the CPU usage of the ice-gnss-<dev_name> thread on my system
from ~90 % to ~8 %.

I am not sure if the larger 0.1 s pause after inserting data into the
gnss subsystem is really necessary, but I'm keeping that as it was.

Of course, ideally the driver would not have to poll at all, but I don't
know if the E810 can watch for GNSS data availability over the i2c bus
by itself and notify the driver.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: use GNSS subsystem instead of TTY

Previously support for GNSS was implemented as a TTY driver, it allowed
to access GNSS receiver on /dev/ttyGNSS_<bus><func>.

Use generic GNSS subsystem API instead of implementing own TTY driver.
The receiver is accessible on /dev/gnss<id>. In case of multiple receivers
in the OS, correct device can be found by enumerating either:
- /sys/class/net/<eth port>/device/gnss/
- /sys/class/gnss/gnss<id>/device/

Using GNSS subsystem is superior to implementing own TTY driver, as the
GNSS subsystem was designed solely for this purpose. It also implements
TTY driver but in a common and defined way.

From user perspective, there is no difference in communicating with a
device, except new path to the device shall be used. The device will
provide same information to the userspace as the old one, and can be used
in the same way, i.e.:
old # gpsmon /dev/ttyGNSS_2100_0
new # gpsmon /dev/gnss0
There is no other impact on userspace tools.

User expecting onboard GNSS receiver support is required to enable
CONFIG_GNSS=y/m in kernel config.

Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Signed-off-by: Michal Michalik <michal.michalik@intel.com>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

ice: Add check for kzalloc

Add the check for the return value of kzalloc in order to avoid
NULL pointer dereference.
Moreover, use the goto-label to share the clean code.

Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: Fix potential memory leak in ice_gnss_tty_write()

The ice_gnss_tty_write() return directly if the write_buf alloc failed,
leaking the cmd_buf.

Fix by free cmd_buf if write_buf alloc failed.

Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: add write functionality for GNSS TTY

Add the possibility to write raw bytes to the GNSS module through the
first TTY device. This allows user to configure the module.

Create a second read-only TTY device.

Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: remove u16 arithmetic in ice_gnss

Change u16 to unsigned int where arithmetic occurs.

Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: use min_t() to make code cleaner in ice_gnss

Fix the following coccicheck warning:
./drivers/net/ethernet/intel/ice/ice_gnss.c:79:26-27: WARNING opportunity for min()

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: fix return value check in ice_gnss.c

kthread_create_worker() and tty_alloc_driver() return ERR_PTR()
and never return NULL. The NULL test in the return value check
should be replaced with IS_ERR().

Fixes: 43113ff73453 ("ice: add TTY for GNSS module for E810T device")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: add TTY for GNSS module for E810T device

Add a new ice_gnss.c file for holding the basic GNSS module functions.
If the device supports GNSS module, call the new ice_gnss_init and
ice_gnss_release functions where appropriate.

Implement basic functionality for reading the data from GNSS module
using TTY device.

Add I2C read AQ command. It is now required for controlling the external
physical connectors via external I2C port expander on E810-T adapters.

Future changes will introduce write functionality.

Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Signed-off-by: Sudhansu Sekhar Mishra <sudhansu.mishra@intel.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>