On 3/9/23 02:33, Dmitry Baryshkov wrote:
On 09/03/2023 00:44, Maximilian Luz wrote:
On 3/8/23 23:16, Rob Herring wrote:
On Sun, Mar 05, 2023 at 03:21:18AM +0100, Maximilian Luz wrote:
Add bindings for the Qualcomm Secure Execution Environment interface
(QSEECOM).
Pretty sure I already asked, but no answer in the commit message. Why do
we need this? You've already declared the platform supports SCM calls
with "qcom,scm". Why can't you probe whether you have QSEECOM or not? DT
is for non-discoverable h/w we are stuck with.
Yes, you've asked this before but I can only repeat what I've written in
my last response to your question: I am not aware of any way to properly
discover the interface at runtime from software.
If it makes you happy, I can put this in the commit message as well...
Why is software made non-discoverable too?
Please direct that question at the Qualcomm guys who actually designed
that interface. I can't give you an answer to that, and I'm not all that
happy about this either.
To reiterate: I've reverse engineered this based on the Windows driver.
The Windows driver loads on an ACPI HID and it doesn't use any function
to check/verify whether the interface is actually present. Adding a DT
entry is the straight-forward adaption to having a HID in ACPI.
Nodes with only a compatible string are usually just an abuse of DT to
instantiate some driver.
If you or anyone here has any idea on how to discover the presence of
this, please feel free to let me know and I'd be happy to implement
that. Until then, I unfortunately don't see any other way of dealing
with this.
You can probably try requesting QSEECOM version. According to msm-3.18:
uint32_t feature = 10;
rc = qseecom_scm_call(6, 3, &feature, sizeof(feature),
&resp, sizeof(resp));
pr_info("qseecom.qsee_version = 0x%x\n", resp.result);
if (rc) {
pr_err("Failed to get QSEE version info %d\n", rc);
goto exit_del_cdev;
}
Thanks! I'll give that a try.
As I can't test this on a device that doesn't have qseecom, it would
probably be a good idea if someone could test this on a device that has
qcom_scm but no qseecom (if those even exist) to make sure this doesn't
misbehave.
Regards,
Max
