[PATCH V3 2/4] ACPI/scan: Clean up acpi_check_dma
From: bhelgaas@google.com (Bjorn Helgaas)
Date: 2015-09-14 16:34:20
Also in:
linux-acpi, linux-pci, lkml
On Wed, Aug 26, 2015 at 08:54:37PM +0700, Suravee Suthikulpanit wrote:
The original name of acpi_check_dma() function does not clearly tell what exactly it is checking. Also, returning two boolean values (one to indicate device is DMA capability, and the other to inidicate device coherency
s/inidicate/indicate/
attribute) can be confusing. So, in order to simplify the function, this patch renames acpi_check_dma() to acpi_check_dma_coherency() to clearly indicate the purpose of this function, and only returns an integer where -1 means DMA not supported, 1 means coherent DMA, and 0 means non-coherent DMA.
I think acpi_check_dma_coherency() is better, but only slightly. It
still doesn't give a hint about the *sense* of the return value. I
think it'd be easier to read if there were two functions, e.g.,
int acpi_dma_supported(struct acpi_device *adev)
{
if (!adev)
return 0;
if (adev->flags.cca_seen)
return 1;
/*
* Per ACPI 6.0 sec 6.2.17, assume devices can do cache-coherent
* DMA on "Intel platforms". Presumably that includes all x86 and
* ia64, and other arches will set CONFIG_ACPI_CCA_REQUIRED=y.
*/
if (!IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED))
return 1;
return 0;
}
int acpi_dma_is_coherent(struct acpi_device *adev)
{
if (!acpi_dma_supported(adev))
return 0;
return adev->flags.coherent_dma;
}
struct platform_device *acpi_create_platform_device(...)
{
...
if (acpi_dma_supported(adev))
pdevinfo.dma_mask = DMA_BIT_MASK(32);
int acpi_bind_one(...)
{
...
if (acpi_dma_supported(acpi_dev))
arch_setup_dma_ops(dev, 0, 0, NULL, retval);
bool device_dma_is_coherent(...)
{
...
return acpi_dma_is_coherent(ACPI_COMPANION(dev)):
quoted hunk ↗ jump to hunk
Also, this patch moves the function into drivers/acpi/scan.c since it is easier to follow the logic in the acpi_init_coherency() in the same file here. Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com> Suggested-by: Bjorn Helgaas <bhelgaas@google.com> Suggested-by: Rafael J. Wysocki <redacted> CC: Catalin Marinas <catalin.marinas@arm.com> CC: Rob Herring <robh+dt@kernel.org> CC: Will Deacon <redacted> --- drivers/acpi/acpi_platform.c | 7 ++++++- drivers/acpi/glue.c | 6 +++--- drivers/acpi/scan.c | 39 +++++++++++++++++++++++++++++++++++++++ drivers/base/property.c | 10 +++++++--- include/acpi/acpi_bus.h | 36 ++---------------------------------- include/linux/acpi.h | 4 ++-- 6 files changed, 59 insertions(+), 43 deletions(-)diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c index 06a67d5..0b17a78 100644 --- a/drivers/acpi/acpi_platform.c +++ b/drivers/acpi/acpi_platform.c@@ -103,7 +103,12 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev) pdevinfo.res = resources; pdevinfo.num_res = count; pdevinfo.fwnode = acpi_fwnode_handle(adev); - pdevinfo.dma_mask = acpi_check_dma(adev, NULL) ? DMA_BIT_MASK(32) : 0; + + if (acpi_check_dma_coherency(adev) < 0) + pdevinfo.dma_mask = 0; + else + pdevinfo.dma_mask = DMA_BIT_MASK(32); + pdev = platform_device_register_full(&pdevinfo); if (IS_ERR(pdev)) dev_err(&adev->dev, "platform device creation failed: %ld\n",diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c index b9657af..9be7f0f 100644 --- a/drivers/acpi/glue.c +++ b/drivers/acpi/glue.c@@ -168,7 +168,6 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev) struct list_head *physnode_list; unsigned int node_id; int retval = -EINVAL; - bool coherent; if (has_acpi_companion(dev)) { if (acpi_dev) {@@ -225,8 +224,9 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev) if (!has_acpi_companion(dev)) ACPI_COMPANION_SET(dev, acpi_dev); - if (acpi_check_dma(acpi_dev, &coherent)) - arch_setup_dma_ops(dev, 0, 0, NULL, coherent); + retval = acpi_check_dma_coherency(acpi_dev); + if (retval >= 0) + arch_setup_dma_ops(dev, 0, 0, NULL, retval); acpi_physnode_link_name(physical_node_name, node_id); retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index ec25635..1d68289 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c@@ -2182,6 +2182,45 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp) kfree(pnp->unique_id); } +/** + * acpi_check_dma_coherency - Check DMA coherency for the specified device. + * @adev: The pointer to acpi device to check coherency attribute + * + * Return -ENOTSUPP if DMA is not supported. Otherwise, return 1 if the + * device support coherent DMA, or 0 for non-coherent DMA. + */ +int acpi_check_dma_coherency(struct acpi_device *adev) +{ + int ret = -ENOTSUPP; + + if (!adev) + return ret;
There's no need for the local "ret". You can "return -ENOTSUPP" here and below, which is easier to read than looking back to see where "ret" was defined and whether it was modified after being initialized.
+ + /** + * Currently, we only support _CCA=1 (i.e. coherent_dma=1) + * This should be equivalent to specifying dma-coherent for + * a device in OF. + * + * For the case when _CCA=0 (i.e. coherent_dma=0 && cca_seen=1), + * we have two choices: + * 1. Do not support and disable DMA.
I know you didn't write this comment, but do we actually *disable* DMA in the sense of turning off PCI bus mastering or calling an ACPI method that disables DMA by this device? I suspect we just don't set up DMA ops and masks for this device.
+ * 2. Support but rely on arch-specific cache maintenance for + * non-coherenje DMA operations.
s/Support but/Support DMA but/ ? s/non-coherenje/non-coherent/
quoted hunk ↗ jump to hunk
+ * Currently, we implement case 2 above. + * + * For the case when _CCA is missing (i.e. cca_seen=0) and + * platform specifies ACPI_CCA_REQUIRED, we do not support DMA, + * and fallback to arch-specific default handling. + * + * See acpi_init_coherency() for more info. + */ + if (!adev->flags.cca_seen && IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED)) + return ret; + + return adev->flags.coherent_dma; +} +EXPORT_SYMBOL_GPL(acpi_check_dma_coherency); + static void acpi_init_coherency(struct acpi_device *adev) { unsigned long long cca = 0;diff --git a/drivers/base/property.c b/drivers/base/property.c index f3f6d16..cd45dfc 100644 --- a/drivers/base/property.c +++ b/drivers/base/property.c@@ -525,10 +525,14 @@ bool device_dma_is_coherent(struct device *dev) { bool coherent = false; - if (IS_ENABLED(CONFIG_OF) && dev->of_node) + if (IS_ENABLED(CONFIG_OF) && dev->of_node) { coherent = of_dma_is_coherent(dev->of_node); - else - acpi_check_dma(ACPI_COMPANION(dev), &coherent); + } else { + int ret = acpi_check_dma_coherency(ACPI_COMPANION(dev)); + + if (ret >= 0) + coherent = ret; + } return coherent; }diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h index 7ecb8e4..baf43ea 100644 --- a/include/acpi/acpi_bus.h +++ b/include/acpi/acpi_bus.h@@ -382,40 +382,6 @@ struct acpi_device { void (*remove)(struct acpi_device *); }; -static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent) -{ - bool ret = false; - - if (!adev) - return ret; - - /** - * Currently, we only support _CCA=1 (i.e. coherent_dma=1) - * This should be equivalent to specifyig dma-coherent for - * a device in OF. - * - * For the case when _CCA=0 (i.e. coherent_dma=0 && cca_seen=1), - * There are two cases: - * case 1. Do not support and disable DMA. - * case 2. Support but rely on arch-specific cache maintenance for - * non-coherence DMA operations. - * Currently, we implement case 2 above. - * - * For the case when _CCA is missing (i.e. cca_seen=0) and - * platform specifies ACPI_CCA_REQUIRED, we do not support DMA, - * and fallback to arch-specific default handling. - * - * See acpi_init_coherency() for more info. - */ - if (adev->flags.coherent_dma || - (adev->flags.cca_seen && IS_ENABLED(CONFIG_ARM64))) { - ret = true; - if (coherent) - *coherent = adev->flags.coherent_dma; - } - return ret; -} - static inline bool is_acpi_node(struct fwnode_handle *fwnode) { return fwnode && fwnode->type == FWNODE_ACPI;@@ -640,6 +606,8 @@ static inline bool acpi_device_can_poweroff(struct acpi_device *adev) return adev->power.states[ACPI_STATE_D3_COLD].flags.valid; } +int acpi_check_dma_coherency(struct acpi_device *adev); + #else /* CONFIG_ACPI */ static inline int register_acpi_bus_type(void *bus) { return 0; }diff --git a/include/linux/acpi.h b/include/linux/acpi.h index d2445fa..d350c9e 100644 --- a/include/linux/acpi.h +++ b/include/linux/acpi.h@@ -562,9 +562,9 @@ static inline int acpi_device_modalias(struct device *dev, return -ENODEV; } -static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent) +static inline int acpi_check_dma_coherency(struct acpi_device *adev) { - return false; + return -ENOTSUPP; } #define ACPI_PTR(_ptr) (NULL)-- 2.1.0