spi/pl022: Add high priority message pump support
This switches the PL022 worker to a kthread in order to get
hold of a mechanism to control the message pump priority. On
low-latency systems elevating the message kthread to realtime
priority give a real sleek response curve. This has been
confirmed by measurements. Realtime priority elevation for
a certain PL022 port can be requested from platform data.
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Chris Blair <chris.blair@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/include/linux/amba/pl022.h b/include/linux/amba/pl022.h
index 572f637..3672f40 100644
--- a/include/linux/amba/pl022.h
+++ b/include/linux/amba/pl022.h
@@ -241,6 +241,8 @@
* @autosuspend_delay: delay in ms following transfer completion before the
* runtime power management system suspends the device. A setting of 0
* indicates no delay and the device will be suspended immediately.
+ * @rt: indicates the controller should run the message pump with realtime
+ * priority to minimise the transfer latency on the bus.
*/
struct pl022_ssp_controller {
u16 bus_id;
@@ -250,6 +252,7 @@
void *dma_rx_param;
void *dma_tx_param;
int autosuspend_delay;
+ bool rt;
};
/**