Messages in this thread | | | Subject | Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver | From | John Garry <> | Date | Tue, 28 Jan 2020 18:22:02 +0000 |
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On 28/01/2020 17:51, Olof Johansson wrote: > Hi, > > On Tue, Jan 28, 2020 at 3:18 AM John Garry <john.garry@huawei.com> wrote: >>
Hi Olof,
>> Add a generic driver for platforms which populate their ACPI PPTT >> processor package ID Type Structure according to suggestion in the ACPI >> spec - see ACPI 6.2, section 5.2.29.3 ID structure Type 2. >> >> The soc_id is from member LEVEL_2_ID. >> >> For this, we need to use a whitelist of platforms which are known to >> populate the structure as suggested. >> >> For now, only the vendor and soc_id fields are exposed. >> >> Signed-off-by: John Garry <john.garry@huawei.com> >> --- >> drivers/soc/Makefile | 1 + >> drivers/soc/acpi_generic.c | 102 +++++++++++++++++++++++++++++++++++++ >> 2 files changed, 103 insertions(+) >> create mode 100644 drivers/soc/acpi_generic.c >> >> diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile >> index 8b49d782a1ab..2a59a30a22cd 100644 >> --- a/drivers/soc/Makefile >> +++ b/drivers/soc/Makefile >> @@ -3,6 +3,7 @@ >> # Makefile for the Linux Kernel SOC specific device drivers. >> # >> >> +obj-$(CONFIG_ACPI_PPTT) += acpi_generic.o >> obj-$(CONFIG_ARCH_ACTIONS) += actions/ >> obj-$(CONFIG_SOC_ASPEED) += aspeed/ >> obj-$(CONFIG_ARCH_AT91) += atmel/ > > Based on everything I've seen so far, this should go under drivers/acpi instead.
soc drivers seem to live in drivers/soc (non-arm32, anyway), so I decided on this location. But drivers/acpi would also seem reasonable now.
> >> diff --git a/drivers/soc/acpi_generic.c b/drivers/soc/acpi_generic.c >> new file mode 100644 >> index 000000000000..34a1f5f8e063 >> --- /dev/null >> +++ b/drivers/soc/acpi_generic.c >> @@ -0,0 +1,102 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (c) John Garry, john.garry@huawei.com >> + */ >> + >> +#define pr_fmt(fmt) "SOC ACPI GENERIC: " fmt >> + >> +#include <linux/acpi.h> >> +#include <linux/sys_soc.h> >> + >> +/* >> + * Known platforms that fill in PPTT package ID structures according to >> + * ACPI spec examples, that being: >> + * - Custom driver attribute is in ID Type Structure VENDOR_ID member >> + * - SoC id is in ID Type Structure LEVEL_2_ID member >> + * See ACPI SPEC 6.2 Table 5-154 for PPTT ID Type Structure >> + */ >> +static struct acpi_platform_list plat_list[] = { >> + {"HISI ", "HIP08 ", 0, ACPI_SIG_PPTT, all_versions}, >> + { } /* End */ >> +}; > > As others have said, this will become a mess over time, and will > require changes for every new platform. Which, unfortunately, is > exactly what ACPI is supposed to provide relief from by making > standardized platforms... standardized. >
Right, and I think that it can be dropped. As discussed with Sudeep, I was concerned how this PPTT ID structure could be interpreted, and had a whitelist as a conservative approach.
>> + >> +struct acpi_generic_soc_struct { >> + struct soc_device_attribute dev_attr; >> + u32 vendor; >> +}; >> + >> +static ssize_t vendor_show(struct device *dev, >> + struct device_attribute *attr, >> + char *buf) >> +{ >> + struct acpi_generic_soc_struct *soc = dev_get_drvdata(dev); >> + u8 vendor_id[5] = {}; >> + >> + *(u32 *)vendor_id = soc->vendor; >> + >> + return sprintf(buf, "%s\n", vendor_id); >> +} >> + >> +static DEVICE_ATTR_RO(vendor); >> + >> +static __init int soc_acpi_generic_init(void) >> +{ >> + int index; >> + >> + index = acpi_match_platform_list(plat_list); >> + if (index < 0) >> + return -ENOENT; >> + >> + index = 0; >> + while (true) { >> + struct acpi_pptt_package_info info; >> + >> + if (!acpi_pptt_get_package_info(index, &info)) { >> + struct soc_device_attribute *soc_dev_attr; >> + struct acpi_generic_soc_struct *soc; >> + struct soc_device *soc_dev; >> + u8 soc_id[9] = {}; >> + >> + *(u64 *)soc_id = info.LEVEL_2_ID; >> + >> + soc = kzalloc(sizeof(*soc), GFP_KERNEL); >> + if (!soc) >> + return -ENOMEM; >> + >> + soc_dev_attr = &soc->dev_attr; >> + soc_dev_attr->soc_id = kasprintf(GFP_KERNEL, "%s", >> + soc_id); >> + if (!soc_dev_attr->soc_id) { >> + kfree(soc); >> + return -ENOMEM; >> + } >> + soc->vendor = info.vendor_id; >> + >> + soc_dev = soc_device_register(soc_dev_attr); >> + if (IS_ERR(soc_dev)) { >> + int ret = PTR_ERR(soc_dev); >> + >> + pr_info("could not register soc (%d) index=%d\n", >> + ret, index); >> + kfree(soc_dev_attr->soc_id); >> + kfree(soc); >> + return ret; >> + } >> + dev_set_drvdata(soc_device_to_device(soc_dev), soc); >> + device_create_file(soc_device_to_device(soc_dev), >> + &dev_attr_vendor); > > Hmm, this doesn't look like much of a driver to me. This looks like > the export of an attribute to userspace, and should probably be done > by ACPI core instead of creating an empty driver for it.
OK, but I'm thinking that having a soc driver can be useful as it is common to DT, and so userspace only has to check a single location. And the soc driver can also cover multiple-chip systems without have to reinvent that code for ACPI core. And it saves adding a new ABI.
> > This would also solve the whitelist issue -- always export this > property if it's set. If it's wrong, then the platform vendor needs to > fix it up. That's the approach that is used for other aspects of the > standardized platforms, right? We don't want to litter the kernel with > white/blacklists -- that's not a net improvement.
Agreed.
> > > -Olof > .
Thanks, John
>
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