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Message-ID: <3346157.KeMTNn1Omm@vostro.rjw.lan>
Date: Thu, 09 Apr 2015 23:43:55 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Cc: mika.westerberg@...ux.intel.com, robert.moore@...el.com,
lv.zheng@...el.com, lenb@...nel.org, hanjun.guo@...aro.org,
catalin.marinas@....com, will.deacon@....com, al.stone@...aro.org,
msalter@...hat.com, gregkh@...uxfoundation.org, leo.duran@....com,
arnd@...db.de, linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org
Subject: Re: [RFC PATCH] ACPI / scan: Introduce _CCA parsing logic and setting up device coherency
On Wednesday, April 01, 2015 10:20:20 AM Suravee Suthikulpanit wrote:
> ACPI v5.1 introduced _CCA object for specifying cache coherency attribute
> for devices. This patch implements a logic, which traverses device namespace
> to parse the coherency information, and calling the corresponded
> arch_setup_dma_ops().
>
> It checks the _CCA during ACPI scan, and setup coherency during acpi_device creation.
> Then, this is propagted to the platform_device when it is created at later time.
>
> CC: Mark Salter <msalter@...hat.com>
> CC: Hanjun Guo <hanjun.guo@...aro.org>
> CC: Al Stone <al.stone@...aro.org>
> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> ---
>
> NOTE:
>
> The original patch has been submitted by Mark Salter, and discussed here:
>
> * http://comments.gmane.org/gmane.linux.acpi.devel/70424
>
> One of the reveiw comment was dissusing whether we need the do/while loop for
> travesing parents of the device. AFAIK, there are no APIs that would do upsearch
> from a particular node. The acpi_get_handle() is the closest one, but it is using
> ACPI_NS_NO_UPSEARCH.
>
> This has been rebased and tested with:
> * http://git.linaro.org/leg/acpi/acpi.git acpi-5.1-v11
> * [V8 PATCH 0/3] Introduce ACPI support for ahci_platform driver
> (https://lkml.org/lkml/2015/3/30/729)
>
> drivers/acpi/acpi_platform.c | 5 +++-
> drivers/acpi/scan.c | 56 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 60 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
> index 1284138..47e37a8 100644
> --- a/drivers/acpi/acpi_platform.c
> +++ b/drivers/acpi/acpi_platform.c
> @@ -108,9 +108,12 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
> if (IS_ERR(pdev))
> dev_err(&adev->dev, "platform device creation failed: %ld\n",
> PTR_ERR(pdev));
> - else
> + else {
> + arch_setup_dma_ops(&pdev->dev, 0, 0, NULL,
> + is_device_dma_coherent(&adev->dev));
> dev_dbg(&adev->dev, "created platform device %s\n",
> dev_name(&pdev->dev));
> + }
>
> kfree(resources);
> return pdev;
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 230ec983..4d81c55 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -11,6 +11,7 @@
> #include <linux/kthread.h>
> #include <linux/dmi.h>
> #include <linux/nls.h>
> +#include <linux/dma-mapping.h>
>
> #include <asm/pgtable.h>
>
> @@ -57,6 +58,9 @@ struct acpi_device_bus_id{
> struct list_head node;
> };
>
> +static int acpi_bus_type_and_status(acpi_handle handle, int *type,
> + unsigned long long *sta);
> +
> void acpi_scan_lock_acquire(void)
> {
> mutex_lock(&acpi_scan_lock);
> @@ -1327,6 +1331,51 @@ void acpi_bus_put_acpi_device(struct acpi_device *adev)
> put_device(&adev->dev);
> }
>
> +/**
> + * acpi_check_and_set_coherency - check and set cache coherency of a device
> + * @device: ACPI device
> + *
> + * Search a device and its parents for a _CCA method and calculate
> + * the effective coherency property of the device. If found, set up
> + * appropriate dma_ops for the device.
> + *
> + * Note From ACPIv5.1 spec:
> + * If used _CCA must be included under all bus-master-capable
> + * devices defined as children of \_SB. The value of _CCA is inherited
> + * by all descendants of these devices, so it need not be repeated for
> + * their children devices and will be ignored by OSPM if it is provided
> + * there.
> + */
> +static int acpi_check_and_set_coherency(struct acpi_device *device)
> +{
> + acpi_status status;
> + unsigned long long eff_cca = ~0ULL;
> + acpi_handle tmp, handle = device->handle;
> +
> + /* Calculate effective _CCA from all parents of this device */
> + do {
> + unsigned long cca;
> +
> + status = acpi_get_handle(handle, "_CCA", &tmp);
> + if (ACPI_SUCCESS(status)) {
> + status = acpi_evaluate_integer(tmp, "_CCA", NULL, &cca);
> + /* Other values besides 0 and 1 are reserved */
> + if (ACPI_FAILURE(status) || (cca != 0 && cca != 1))
> + return -EINVAL;
> + eff_cca = cca;
> + }
> +
> + status = acpi_get_parent(handle, &handle);
So if I'm not mistaken, this is going to evaluate _CCA for all of the ancestors
of the device even though it already might have been evaluated for all of them.
Any chance to optimize it somewhat?
> + if (ACPI_FAILURE(status))
> + break;
> + } while (ACPI_SUCCESS(status));
> +
> + if (eff_cca != ~0ULL)
> + arch_setup_dma_ops(&device->dev, 0, 0, NULL, eff_cca);
> +
> + return 0;
> +}
> +
> int acpi_device_add(struct acpi_device *device,
> void (*release)(struct device *))
> {
> @@ -1398,6 +1447,13 @@ int acpi_device_add(struct acpi_device *device,
> device->dev.parent = &device->parent->dev;
> device->dev.bus = &acpi_bus_type;
> device->dev.release = release;
> +
> + result = acpi_check_and_set_coherency(device);
> + if (result) {
> + dev_err(&device->dev, "Error getting device _CCA information\n");
> + goto err;
> + }
> +
> result = device_add(&device->dev);
> if (result) {
> dev_err(&device->dev, "Error registering device\n");
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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