McSPI hangs with cs_change after "Switch driver to use transfer_one" change

Hi All,

I'm in a use case where I use cs_change on McSPI channel 3 on a single transfer Full-Duplex message, then I transfer a single full duplex message without cs_change on channel 1.

Here is a better representation :
-- 1 transfer message cs_change=1
cs3 : set_cs(0)
cs3 : full-duplex transfer
cs3 : transfer ok
-- 1 transfer message cs_change=1
cs3 : set_cs(0)
cs3 : full-duplex transfer
cs3 : transfer ok
...
-- 1 transfer message cs_change=1
cs3 : set_cs(0)
cs3 : full-duplex transfer
cs3 : transfer ok
-- 1 transfer message cs_change=1
cs1 : set_cs(0)
cs1 : full-duplex transfer
cs1 : RXS timed out
cs1 : set_cs(1)

Then "RXS timed out" on each non-cs3 transfers.

The previous behavior of cs_change was :
- between transfers, unassert CS and re-assert-it for the following transfer
- between messages, unassert CS

The new behaviour inherited from the SPI core spi_transfer_one_message function :
- between transfers, unassert CS and re-assert-it for the following transfer
- between messages, leave CS asserted

We tried disabling the DMA, and the FIFO, but the behavior was actually the same, only reverting back before the "Switch driver to use transfer_one" fixed the issue.

Then actually disabling the cs_change corrected the issue. It may be why the original driver ignored the "leave it on after last xfer" hint.

The problem is : how can we disable this hint since it is managed in SPI core spi_transfer_one_message ?

A solution will be to track down the current asserted CS and unassert it them when the active channel changes.

Neil

Looks like bus contention here.

It seems the core driver assumes that the driver is smart enough to deselect the previous chip select instead of doing it explicitly.

--
To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html