Unverified Commit 809b1b04 authored by Robin Gong's avatar Robin Gong Committed by Mark Brown
Browse files

spi: introduce fallback to pio 



Add fallback to pio mode in case dma transfer failed with error status
SPI_TRANS_FAIL_NO_START.
If spi client driver want to enable this feature please set xfer->error in
the proper place such as dmaengine_prep_slave_sg() failure detect(but no
any data put into spi bus yet). Besides, add master->fallback checking in
its can_dma() so that spi core could switch to pio next time. Please refer
to spi-imx.c.

Signed-off-by: default avatarRobin Gong <yibin.gong@nxp.com>
Link: https://lore.kernel.org/r/1592347329-28363-2-git-send-email-yibin.gong@nxp.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent c314360c

drivers/spi/spi.c

+12 −0
Original line number Diff line number Diff line
@@ -982,6 +982,8 @@ static int __spi_unmap_msg(struct spi_controller *ctlr, struct spi_message *msg) 
		spi_unmap_buf(ctlr, tx_dev, &xfer->tx_sg, DMA_TO_DEVICE);

	}



	ctlr->cur_msg_mapped = false;



	return 0;

}

#else /* !CONFIG_HAS_DMA */
@@ -1234,8 +1236,17 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, 
		if (xfer->tx_buf || xfer->rx_buf) {

			reinit_completion(&ctlr->xfer_completion);



fallback_pio:

			ret = ctlr->transfer_one(ctlr, msg->spi, xfer);

			if (ret < 0) {

				if (ctlr->cur_msg_mapped &&

				   (xfer->error & SPI_TRANS_FAIL_NO_START)) {

					__spi_unmap_msg(ctlr, msg);

					ctlr->fallback = true;

					xfer->error &= ~SPI_TRANS_FAIL_NO_START;

					goto fallback_pio;

				}



				SPI_STATISTICS_INCREMENT_FIELD(statm,

							       errors);

				SPI_STATISTICS_INCREMENT_FIELD(stats,
@@ -1693,6 +1704,7 @@ void spi_finalize_current_message(struct spi_controller *ctlr) 
	spin_lock_irqsave(&ctlr->queue_lock, flags);

	ctlr->cur_msg = NULL;

	ctlr->cur_msg_prepared = false;

	ctlr->fallback = false;

	kthread_queue_work(&ctlr->kworker, &ctlr->pump_messages);

	spin_unlock_irqrestore(&ctlr->queue_lock, flags);

include/linux/spi/spi.h

+7 −0
Original line number Diff line number Diff line
@@ -447,6 +447,8 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv) 
 *	If the driver does not set this, the SPI core takes the snapshot as

 *	close to the driver hand-over as possible.

 * @irq_flags: Interrupt enable state during PTP system timestamping

 * @fallback: fallback to pio if dma transfer return failure with

 *	SPI_TRANS_FAIL_NO_START.

 *

 * Each SPI controller can communicate with one or more @spi_device

 * children.  These make a small bus, sharing MOSI, MISO and SCK signals
@@ -602,6 +604,7 @@ struct spi_controller { 
	bool				auto_runtime_pm;

	bool                            cur_msg_prepared;

	bool				cur_msg_mapped;

	bool                            fallback;

	struct completion               xfer_completion;

	size_t				max_dma_len;
@@ -847,6 +850,7 @@ extern void spi_res_release(struct spi_controller *ctlr, 
 *	back unset and they need the better resolution.

 * @timestamped_post: See above. The reason why both exist is that these

 *	booleans are also used to keep state in the core SPI logic.

 * @error: Error status logged by spi controller driver.

 *

 * SPI transfers always write the same number of bytes as they read.

 * Protocol drivers should always provide @rx_buf and/or @tx_buf.
@@ -940,6 +944,9 @@ struct spi_transfer { 
	bool		timestamped;



	struct list_head transfer_list;



#define SPI_TRANS_FAIL_NO_START	BIT(0)

	u16		error;

};



/**

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