Re: [PATCH] soc: hisilicon: Support HCCS driver on Kunpeng SoC

[lihuisong (C)]

Hi Arnd,

Thanks for your review. My reply is as follows.


在 2023/4/24 16:09, Arnd Bergmann 写道:
> On Mon, Apr 24, 2023, at 09:30, Huisong Li wrote:
>
> > diff --git a/drivers/soc/hisilicon/Kconfig
> > b/drivers/soc/hisilicon/Kconfig
> > new file mode 100644
> > index 000000000000..81768d47f572
> > --- /dev/null
> > +++ b/drivers/soc/hisilicon/Kconfig
> > @@ -0,0 +1,18 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +
> > +menu "Hisilicon SoC drivers"
> > +	depends on ARCH_HISI
> > +
> > +config KUNPENG_HCCS
> > +	tristate "HCCS driver on Kunpeng SoC"
> > +	depends on ARM64 && ACPI
> Is there a compile-time dependency on ARM64? If not, it would
Yes, no compile-time dependency on ARM64.
> be good to allow compile testing. At the same time, you
> can probably tighten this to ARCH_HISI instead of ARM64,
> since no other vendors are going to use it:
>
>         depends on ACPI
>         depends on (ARM64 && ARCH_HISI) || COMPILE_TEST
What do you think of adjusting it as below?
menu "Hisilicon SoC drivers"
    depends on ARCH_HISI || COMPILE_TEST

config KUNPENG_HCCS
    depends on ACPI
    depends on ARM64 || COMPILE_TEST

> > +
> > +#include "kunpeng_hccs.h"
> > +
> > +/* PCC defines */
> > +#define HCCS_PCC_SIGNATURE_MASK		0x50434300
> > +#define HCCS_PCC_STATUS_CMD_COMPLETE	BIT(0)
> Should these perhaps be in include/acpi/pcc.h? The 0x50434300
> number is just "PCC\0", so it appears to not be HCCS specific.
This is a PCC signature. As stated in the APCI,
"The signature of a subspace is computed by a bitwiseor of the value 
0x50434300
with the subspace ID. For example, subspace 3 has the signature 0x50434303."

I am not sure if all driver need to use this fixed signature mask.
As far as I know, cppc_acpi.c didn't use this signature and 
xgene-hwmon.c used another mask defined in its driver.
So I place it here.
> > +
> > +static int hccs_get_device_property(struct hccs_dev *hdev)
> > +{
> > +	struct device *dev = hdev->dev;
> > +
> > +	if (device_property_read_u32(dev, "device-flags", &hdev->flags)) {
> > +		dev_err(hdev->dev, "no device-flags property.\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	if (device_property_read_u8(dev, "pcc-type", &hdev->type)) {
> > +		dev_err(hdev->dev, "no pcc-type property.\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	if (device_property_read_u32(dev, "pcc-chan-id", &hdev->chan_id)) {
> > +		dev_err(hdev->dev, "no pcc-channel property.\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	hdev->intr_mode = hccs_get_bit(hdev->flags, HCCS_DEV_FLAGS_INTR_B);
> > +	if (!hccs_dev_property_supported(hdev))
> > +		return -EOPNOTSUPP;
> > +
> Where are the device properties documented? I'm never quite sure how
> to handle these for ACPI-only drivers, since we don't normally have the
> bindings in Documentation/devicetree/bindings/, but it feels like there
> should be some properly reviewed document somewhere else.
These are ACPI-only, instead of DT.
I will add a comment here as Krzysztof suggested.
> Adding ACPI and devicetree maintainers to Cc for clarification.
>
> > +static int hccs_check_chan_cmd_complete(struct hccs_dev *hdev)
> > +{
> > +	struct hccs_mbox_client_info *cl_info = &hdev->cl_info;
> > +	struct acpi_pcct_shared_memory *comm_base = cl_info->pcc_comm_addr;
> > +	u16 status;
> > +	int ret;
> > +
> > +	/*
> > +	 * Poll PCC status register every 3us(delay_us) for maximum of
> > +	 * deadline_us(timeout_us) until PCC command complete bit is set(cond)
> > +	 */
> > +	ret = readw_relaxed_poll_timeout(&comm_base->status, status,
> > +					 status & HCCS_PCC_STATUS_CMD_COMPLETE,
> > +					 HCCS_POLL_STATUS_TIME_INTERVAL_US,
> > +					 cl_info->deadline_us);
> Is it both safe and faster to use a relaxed readw here, compared
> to the normal one? If there is any access to shared memory
> involved, you need the implied barrier for serialization, and since this
> is already a sleeping operation, I would guess that you don't care
> about the last nanosecond of latency here.
Great comment. I will use the normal one.
> > +static ssize_t hccs_show(struct kobject *k, struct attribute *attr,
> > char *buf)
> > +{
> > +	struct kobj_attribute *kobj_attr;
> > +
> > +	kobj_attr = container_of(attr, struct kobj_attribute, attr);
> > +
> > +	return kobj_attr->show(k, kobj_attr, buf);
> > +}
> > +
> > +static const struct sysfs_ops hccs_comm_ops = {
> > +	.show = hccs_show,
> > +};
> Every sysfs interface needs to be documented in Documentation/ABI/
All right, I will add another patch to do this.
> > diff --git a/drivers/soc/hisilicon/kunpeng_hccs.h
> > b/drivers/soc/hisilicon/kunpeng_hccs.h
> > new file mode 100644
> > index 000000000000..ca557ef115ea
> > --- /dev/null
> > +++ b/drivers/soc/hisilicon/kunpeng_hccs.h
> > @@ -0,0 +1,204 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/* Copyright (c) 2023 Hisilicon Limited. */
> > +
> > +#ifndef __KUNPENG_HCCS_H__
> > +#define __KUNPENG_HCCS_H__
> Are you planning to add more drivers that share this file? If not,
> just fold the contents into the driver itself.
Yes, we will add more drivers in this file.