Hi Stefano, all
I am using an b43-compatible SDIO card in an embedded system. It works,
when the SD host controller is used in PIO mode, but fails, if it is used
in DMA mode, whereas I can use normal SD cards in both modes. Now details:
The card is an "SD-Link11g" from "C-guys, Inc.", Taiwan. Chip ID
14e4:4318.
The system is an SuperH sh7724 based "ecovec" board with an SDHI
controller, using the tmio_mmc SD host driver in
drivers/mmc/host/tmio_mmc.c with the drivers/mfd/sh_mobile_sdhi.c MFD
glue. Recently I have extended the tmio driver to also work in DMA mode,
using the SH dmaengine driver drivers/dma/shdma.c. This works with normal
SD cards. SDIO is used so far with polled interrupts.
The problem: in DMA mode the initialisation is performed without any
visible problems. The card is recognised, the frmware is loaded. When the
wpa-supplicant is started, authentication seems to perform correctly too,
but association fails. On the low mmc level I see a number of packets
being exchanged, the last successful packet is reading of 4 bytes from
address 0, using command 53, which returns the same 4 bytes as always -
all seems good so far. After it a write is attempted of 72 bytes, which
are split into two packets of 64 and 8 bytes respectively. As the first
packet is scheduled, DMA transfers it into the SDHI FIFO and calls the
completion method, but already in that completion method I see status bit
"busy" set in SDHI. Normally after such a bit is set, the currently
running execution completes and a completion interrupt is generated.
However, in this case no interrupt is coming, the busy bit remains set and
no further operation is possible.
It is always exactly the same packet shortly after the beginning of the
association process.
I so far have exhausted my creativity, debugging the SDHI controller. In
principle I can see two possible reasons for this problem: either the SDHI
controller hangs, or the card. Since the controller doesn't care what data
and to what addresses is transferred, and it has successfully transferred
a fair amount of data before this point, I think, it is likely, that it is
the card, that is hanging. Therefore my question: how can I debug this
problem at the card level?
Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/