Unverified Commit abb4b46c authored by David Lechner's avatar David Lechner Committed by Mark Brown
Browse files

spi: axi-spi-engine: move msg finalization out of irq handler 



As a general principal, it is best to do as little as possible in an
interrupt handler. This patch reworks the AXI SPI Engine driver to move
timer_delete_sync() and spi_finalize_current_message() out of the
interrupt handler. Instead, spi_finalize_current_message() is moved to
the transfer_one_message function (similar to nearly all other SPI
controllers). A completion is now used to wait for the sync interrupt
that indicates that the message is complete. The watchdog timer is no
longer needed since we can use the wait_for_completion_timeout()
function to wait for the message to complete with the same effect.

As a bonus, these changes also improve throughput of the SPI controller.
For example, this was tested on a ZynqMP with a 80MHz SCLK reading 4
byte samples from an ADC. The max measured throughput increased from
26k to 28k samples per second.

Reviewed-by: default avatarNuno Sa <nuno.sa@analog.com>
Signed-off-by: default avatarDavid Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20240207-axi-spi-engine-round-2-1-v2-2-40c0b4e85352@baylibre.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 531860e1

drivers/spi/spi-axi-spi-engine.c

+15 −25
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
 */



#include <linux/clk.h>

#include <linux/completion.h>

#include <linux/fpga/adi-axi-common.h>

#include <linux/interrupt.h>

#include <linux/io.h>
@@ -13,7 +14,6 @@ 
#include <linux/module.h>

#include <linux/platform_device.h>

#include <linux/spi/spi.h>

#include <linux/timer.h>



#define SPI_ENGINE_REG_RESET			0x40
@@ -109,9 +109,7 @@ struct spi_engine { 
	spinlock_t lock;



	void __iomem *base;

	struct timer_list watchdog_timer;

	struct spi_controller *controller;



	struct completion msg_complete;

	unsigned int int_enable;

};
@@ -483,11 +481,9 @@ static irqreturn_t spi_engine_irq(int irq, void *devid) 


	if (pending & SPI_ENGINE_INT_SYNC && msg) {

		if (completed_id == AXI_SPI_ENGINE_CUR_MSG_SYNC_ID) {

			if (timer_delete_sync(&spi_engine->watchdog_timer)) {

			msg->status = 0;

			msg->actual_length = msg->frame_length;

				spi_finalize_current_message(host);

			}

			complete(&spi_engine->msg_complete);

			disable_int |= SPI_ENGINE_INT_SYNC;

		}

	}
@@ -558,7 +554,7 @@ static int spi_engine_transfer_one_message(struct spi_controller *host, 
	unsigned int int_enable = 0;

	unsigned long flags;



	mod_timer(&spi_engine->watchdog_timer, jiffies + msecs_to_jiffies(5000));

	reinit_completion(&spi_engine->msg_complete);



	spin_lock_irqsave(&spi_engine->lock, flags);
@@ -580,21 +576,16 @@ static int spi_engine_transfer_one_message(struct spi_controller *host, 
	spi_engine->int_enable = int_enable;

	spin_unlock_irqrestore(&spi_engine->lock, flags);



	return 0;

}



static void spi_engine_timeout(struct timer_list *timer)

{

	struct spi_engine *spi_engine = from_timer(spi_engine, timer, watchdog_timer);

	struct spi_controller *host = spi_engine->controller;



	if (WARN_ON(!host->cur_msg))

		return;



	if (!wait_for_completion_timeout(&spi_engine->msg_complete,

					 msecs_to_jiffies(5000))) {

		dev_err(&host->dev,

			"Timeout occurred while waiting for transfer to complete. Hardware is probably broken.\n");

	host->cur_msg->status = -ETIMEDOUT;

		msg->status = -ETIMEDOUT;

	}



	spi_finalize_current_message(host);



	return msg->status;

}



static void spi_engine_release_hw(void *p)
@@ -625,8 +616,7 @@ static int spi_engine_probe(struct platform_device *pdev) 
	spi_engine = spi_controller_get_devdata(host);



	spin_lock_init(&spi_engine->lock);

	timer_setup(&spi_engine->watchdog_timer, spi_engine_timeout, TIMER_IRQSAFE);

	spi_engine->controller = host;

	init_completion(&spi_engine->msg_complete);



	spi_engine->clk = devm_clk_get_enabled(&pdev->dev, "s_axi_aclk");

	if (IS_ERR(spi_engine->clk))