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If dma_pfn_offset is not inherited correctly from the host controller, it might result in sub-optimal configuration as bounce buffer limit might be set to less than optimal level. Consider the mass storage device case. USB storage driver creates a scsi host for the mass storage interface in drivers/usb/storage/usb.c The scsi host parent device is nothing but the the USB interface device. Now, __scsi_init_queue() calls scsi_calculate_bounce_limit() to find out and set the block layer bounce limit. scsi_calculate_bounce_limit() uses dma_max_pfn(host_dev) to get the bounce_limit. host_dev is nothing but the device representing the mass storage interface. If that device doesn't have the right dma_pfn_offset, then dma_max_pfn() is messed up and the bounce buffer limit is wrong. e.g. On Keystone 2 systems, dma_max_pfn() is 0x87FFFF and dma_mask_pfn is 0xFFFFF. Consider a mass storage use case: Without this patch, usb scsi host device (usb-storage) will get a dma_pfn_offset of 0 resulting in a dma_max_pfn() of 0xFFFFF within the scsi layer (scsi_calculate_bounce_limit()). This will result in bounce buffers being unnecessarily used. Hint: On 32-bit ARM platforms dma_max_pfn() = dma_mask_pfn + dma_pfn_offset Signed-off-by: Roger Quadros <rogerq@ti.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| .. | ||
| buffer.c | ||
| config.c | ||
| devices.c | ||
| devio.c | ||
| driver.c | ||
| endpoint.c | ||
| file.c | ||
| generic.c | ||
| hcd-pci.c | ||
| hcd.c | ||
| hub.c | ||
| hub.h | ||
| Kconfig | ||
| Makefile | ||
| message.c | ||
| notify.c | ||
| of.c | ||
| otg_whitelist.h | ||
| port.c | ||
| quirks.c | ||
| sysfs.c | ||
| urb.c | ||
| usb-acpi.c | ||
| usb.c | ||
| usb.h | ||