allocating them on the stack of various bus_dmamap_load*() functions. The
S/G lists are stored in the DMA tags. This matches the implementation on
all other platforms.
Discussed with: scottl, gibbs
Tested by: stas (arm@)
pmap_get_pv_entry(). In fact, some callers already held it around calls.
(In earlier versions, the same statements would apply to the page queues
lock.)
While I'm here tidy up the style of a few nearby statements and revise
some comments.
Tested by: Ian Lepore
o Disable multi-block operations: they sometimes fail.
o Don't use the PROOF bits yet: they hang the system hard.
o Disable the the multi-block operations for !rm9200, but it
still doesn't help.
o Fix writing < 12 bytes errata to actually work.
o Enable, for the moment, reporting extra bytes soaked up.
restructuring of the driver. I've tried to preserve the other silicon
workarounds that we've added over the years, but haven't had a chance
to extensively test on other hardware. On my AT91RM9200 with 30MHz/1
wire/64 block transfers, I've been able to go from ~.66MB/s to
2.25MB/s in the simple tests I performed, almost a 3.5x improvement.
This cuts the boot time almost in half when everything else goes
right (timed from rtc message to login: prompt).
PR: 155214
Submitted by: Ian Lapore
explicltly enable that. The driver chose to use 60MHz / 2 (30MHz)
most of the time rather than 60MHz / 4 (15MHz) based on the Linux
driver of the time. This pushes the spec a little in order to not
suffer the penalty of running at 15MHz. However, when other bus
masters are active in the system, and the user tries 4-wire mode, the
internal bus arbitration would fail with data loss as a result.
# Comments from PR were reworked to reflect my historical perspective
PR: 155214 (partial)
Submitted by: Ian Lepore
BUS_DMA_COHERENT attribute
The minimum unit for changing "cachable" attribute is page, so call
to pmap_change_attr effectively disable cache for all pages that newly
allocated DMA memory region spans on. The problem is that general-purpose
memory could reside on these pages too and disabling cache might affect
performance. Moreover ldrex/strex operators raise Data Abort exception
when accessing memory on page with "cachable" attribute off.
BUS_DMA_COHERENT does nto require memory to be coherent. It just suggests
to do best effort for reducing synchronization overhead.
frequencies. The maximum freqency is 100 kHz according to the datasheet.
- Add child device probing support based on the device tree. It now tries to
find i2c-address property in the tree and attach the device with given slave
address to iicbus.
