DMA on this hardware is limited to dealing with a 4096 bytes at a
time. Previously, the driver was set up accordingly to request single-page
DMA buffers, however that had the effect of generating a large number
of small MMC requests for data I/O.
Improve the driver to accept multi-entry scatter-gather lists. The size of
each entry is already capped to 4096 bytes (AU6601_MAX_DMA_BLOCK_SIZE),
matching the hardware requirements. Existing driver code already iterates
through remaining sglist entries after each DMA transfer is complete.
Also add some comments to help clarify the situation, and clear up
some of the confusion I had regarding DMA vs PIO.
Testing with dd, this increases write performance from 2mb/sec to
10mb/sec, and increases read performance from 4mb/sec to 14mb/sec.
Signed-off-by: Daniel Drake <drake@endlessm.com>
Link: http://lkml.kernel.org/r/CAD8Lp47JYdZzbV9F+asNwvSfLF_po_J7ir6R_Vb-Dab21_=Krw@mail.gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This driver provides support for Alcor Micro AU6601 and AU6621
card readers.
This is single LUN HW and it is expected to work with following standards:
- Support SDR104 / SDR50
- MultiMedia Card (MMC)
- Memory Stick (MS)
- Memory Stick PRO (MS_Pro)
Since it is a PCIe controller, it should work on any architecture
supporting PCIe. For now, it was developed and tested only on x86_64.
This driver is a result of RE work and was created without any
documentation or real knowledge of HW internals.
Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
