Hello Haixu,
Thanks. This was a hard one. I knew that I did the delay settingsmost
probably somewhat wrong but I had no idea that I did it so wrong.
Reworked, made a new function for this, currently testing. Added the
link to the place where your E-Mail is stored
https://lore.kernel.org/all/6171c1c3-55ba-4f74-ae60-764820cf1caf@xxxxxxxxxxx/
as a comment to the source code and hope this will survive the reviews.
Another option would be to add the diagram + the explanations below as
quoted here as comment to the code. Whether 30+ lines of comments would
survive the reviews I don't know.
Just to say nothing in the code making live hard for people trying to
understand the code is something I would like to avoid.
Regards
Harald
On 30.01.24 04:21, Haixu Cui wrote:
. . . . . . . . . .
Delay + A + + B + + C + D + E + F + A +
. . . . . . . . . .
___. . . . . . .___.___. .
CS# |___.______.____.____.___.___| . |___._____________
. . . . . . . . . .
. . . . . . . . . .
SCLK__.___.___NNN_____NNN__.___.___.___.___.___.___NNN_______
NOTE: 1st transfer has two words, the delay betweent these two words
are 'B' in the diagram.
A => struct spi_device -> cs_setup
B => max{struct spi_transfer -> word_delay,
struct spi_device -> word_delay}
Note: spi_device and spi_transfer both have word_delay, Linux
choose the bigger one, refer to _spi_xfer_word_delay_update
function
C => struct spi_transfer -> delay
D => struct spi_device -> cs_hold
E => struct spi_device -> cs_inactive
F => struct spi_transfer -> cs_change_delay
So the corresponding relationship:
A <===> cs_setup_ns (after CS asserted)
B <===> word_delay_ns (no matter with CS)
C+D <===> cs_delay_hold_ns (before CS deasserted)
E+F <===> cs_change_delay_inactive_ns (after CS deasserted, these two
values also recommend in Linux driver to be added up)
