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staging: gasket: add dma_bit_mask module parameter.

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This allows to force dma buffers to be located in 32bit low address
space to workaround issues with some pcie controllers.

Change-Id: I7f77081882b6dffb91f034f8491ad8ffa1375fe7
Signed-off-by: Leonid Lobachev <leonidl@google.com>
This commit is contained in:
Leonid Lobachev
2019-09-25 10:43:59 -07:00
parent ee04262273
commit f003a96909
1 changed files with 13 additions and 2 deletions
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15
gasket_core.c
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@@ -103,6 +103,16 @@ enum gasket_sysfs_attribute_type {
ATTR_USER_MEM_RANGES
};
/* On some arm64 systems pcie dma controller can only access lower 4GB of
* addresses. Unfortunately vendor BSP isn't providing any means of determining
* this limitation and there're no errors reported if access to higher addresses
* if being done. This parameter allows to workaround this issue by pretending
* that our device only supports 32 bit addresses. This in turn will cause
* dma driver to use shadow buffers located in low 32 bit address space.
*/
static int dma_bit_mask = 64;
module_param(dma_bit_mask, int, 0644);
/* Perform a standard Gasket callback. */
static inline int
check_and_invoke_callback(struct gasket_dev *gasket_dev,
@@ -316,8 +326,9 @@ static int gasket_map_pci_bar(struct gasket_dev *gasket_dev, int bar_num)
goto fail;
}
dma_set_mask(&gasket_dev->pci_dev->dev, DMA_BIT_MASK(64));
dma_set_coherent_mask(&gasket_dev->pci_dev->dev, DMA_BIT_MASK(64));
dma_set_mask(&gasket_dev->pci_dev->dev, DMA_BIT_MASK(dma_bit_mask));
dma_set_coherent_mask(&gasket_dev->pci_dev->dev,
DMA_BIT_MASK(dma_bit_mask));
return 0;