On 1/11/2018 1:40 PM, Guenter Roeck wrote:
On Thu, Jan 11, 2018 at 11:47:01AM -0800, Jae Hyun Yoo wrote:
On 1/10/2018 1:47 PM, Guenter Roeck wrote:
On Tue, Jan 09, 2018 at 02:31:26PM -0800, Jae Hyun Yoo wrote:
This commit adds driver implementation for a generic PECI hwmon.
Signed-off-by: Jae Hyun Yoo <jae.hyun....@linux.intel.com>
[ ... ]
+
+ if (priv->temp.tcontrol.valid &&
+ time_before(jiffies, priv->temp.tcontrol.last_updated +
+ UPDATE_INTERVAL_MIN))
+ return 0;
+
Is the delay necessary ? Otherwise I would suggest to drop it.
It adds a lot of complexity to the driver. Also, if the user polls
values more often, that is presumably on purpose.
I was intended to reduce traffic on PECI bus because it's low speed single
wired bus, and temperature values don't change frequently because the value
is sampled and averaged in CPU itself. I'll keep this.
Then please try to move the common code into a single function.
That makes sense. I'll move the common code into a single function.
[ ... ]
+
+ rc = of_property_read_u32(np, "cpu-id", &priv->cpu_id);
What entity determines cpu-id ?
CPU ID numbering is determined by hardware SOCKET_ID strap pins. In this
driver implementation, cpu-id is being used as CPU client indexing.
Seems to me the necessary information to identify a given CPU should
be provided by the PECI core. Also, there are already "cpu" nodes
in devicetree which, if I recall correctly, may include information
such as CPU Ids.
This driver is implemented to support only BMC (Baseboard Management
Controllers) chipset which is running on a separated linux kernel from a
host server system. Through a PECI connection between them, this driver
collects the host server system's CPU and DIMM temperature information
which is running on a separated OS. That could be a linux, a Windows OS
or any other OSes. I mean, there is no shared devicetree data between
them so it is why the 'cpu_id' was added into dt configuration of this
driver.
Using quite limited hardware connections such as PECI, KSC, eSPI and
SMBus, the BMC manages the host server and this hwmon is one of features
of BMC.
+ if (rc || priv->cpu_id >= CPU_ID_MAX) {
+ dev_err(dev, "Invalid cpu-id configuration\n");
+ return rc;
+ }
+
+ rc = of_property_read_u32(np, "dimm-nums", &priv->dimm_nums);
This is an odd devicetree attribute. Normally the number of DIMMs
is dynamic. Isn't there a means to get all that information dynamically
instead of having to set it through devicetree ? What if someone adds
or removes a DIMM ? Who updates the devicetree ?
It means the number of DIMM slots each CPU has, doesn't mean the number of
currently installed DIMM components. If a DIMM is inserted a slot, CPU
reports its actual temperature but on empty slot, CPU reports 0 instead of
reporting an error so it is the reason why this driver enumerates all DIMM
slots' attribute.
And there is no other means to get the number of DIMM slots per CPU ?
It just seems to be that this is the wrong location to provide such
information.
This devicetree attribute will be configured at runtime using dt overlay
based on the host server's hardware configuration which will be parsed
and managed by a userspace BMC service.
[ ... ]
+
+static const struct of_device_id peci_of_table[] = {
+ { .compatible = "peci-hwmon", },
This does not look like a reference to some piece of hardware.
This driver provides generic PECI hwmon function to which controller has
PECI HW such as Aspeed or Nuvoton BMC chip so it's not dependant on a
specific hardware. Should I remove this or any suggestion?
I don't really know enough about the system to make a recommendation.
It seems to me that the PECI core should identify which functionality
it supports and instantiate the necessary driver(s). Maybe there should
be sub-nodes to the peci node with relevant information. Those sub-nodes
should specify the supported functionality in more detail, though -
such as indicating the supported CPU and/or DIMM sensors.
Guenter
As I explained above, BMC and host server are running on separated OSes
so this driver cannot be (actually, doesn't need to be) directly
associated with other kernel modules in the BMC side OS for identifying
the host server system's functionality. My thought is, this driver will
use PECI only for identifying the host server's CPU and DIMM information
and the userspace BMC service could deliver any additional host server
information thru dt overlay if needed before the BMC service initiates
this driver at runtime.
Thanks a lot,
Jae
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