-
Notifications
You must be signed in to change notification settings - Fork 55.3k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
spi: sun4i: Allow transfers larger than FIFO size
SPI transfers were limited to one FIFO depth, which is 64 bytes. This was an artificial limitation, however, as the hardware can handle much larger bursts. To accommodate this, we enable the interrupt when the Rx FIFO is 3/4 full, and drain the FIFO within the interrupt handler. The 3/4 ratio was chosen arbitrarily, with the intention to reduce the potential number of interrupts. Since the SUN4I_CTL_TP bit is set, the hardware will pause transmission whenever the FIFO is full, so there is no risk of losing data if we can't service the interrupt in time. For the Tx side, enable and use the Tx FIFO 3/4 empty interrupt to replenish the FIFO on large SPI bursts. This requires more care in when the interrupt is left enabled, as this interrupt will continually trigger when the FIFO is less than 1/4 full, even though we acknowledge it. Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Olliver Schinagl <o.schinagl@ultimaker.com> Signed-off-by: Mark Brown <broonie@kernel.org>
- Loading branch information
Showing
1 changed file
with
67 additions
and
8 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters