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Commit 5f52c355 authored by Guennadi Liakhovetski's avatar Guennadi Liakhovetski Committed by Chris Ball
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mmc: tmio: use PIO for short transfers 



This patch allows transferring of some requests in PIO and some in DMA
mode and defaults to using DMA only for transfers longer than 8 bytes.
This is especially useful with SDIO, which can have lots of 2- and 4-byte
transfers, creating unnecessary high overhead, when executed in DMA.

Signed-off-by: default avatarGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: default avatarPaul Mundt <lethal@linux-sh.org>
Signed-off-by: default avatarChris Ball <cjb@laptop.org>
parent 51fc7b2c

drivers/mmc/host/tmio_mmc.c

+23 −10
Original line number Diff line number Diff line
@@ -100,6 +100,8 @@ 
		TMIO_STAT_CARD_REMOVE | TMIO_STAT_CARD_INSERT)

#define TMIO_MASK_IRQ     (TMIO_MASK_READOP | TMIO_MASK_WRITEOP | TMIO_MASK_CMD)



#define TMIO_MIN_DMA_LEN 8



#define enable_mmc_irqs(host, i) \

	do { \

		u32 mask;\
@@ -147,6 +149,7 @@ struct tmio_mmc_host { 
	struct platform_device *pdev;



	/* DMA support */

	bool			force_pio;

	struct dma_chan		*chan_rx;

	struct dma_chan		*chan_tx;

	struct tasklet_struct	dma_complete;
@@ -385,6 +388,7 @@ static void tmio_mmc_reset_work(struct work_struct *work) 
	host->cmd = NULL;

	host->data = NULL;

	host->mrq = NULL;

	host->force_pio = false;



	spin_unlock_irqrestore(&host->lock, flags);
@@ -404,6 +408,7 @@ tmio_mmc_finish_request(struct tmio_mmc_host *host) 
	host->mrq = NULL;

	host->cmd = NULL;

	host->data = NULL;

	host->force_pio = false;



	cancel_delayed_work(&host->delayed_reset_work);
@@ -485,7 +490,7 @@ static void tmio_mmc_pio_irq(struct tmio_mmc_host *host) 
	unsigned int count;

	unsigned long flags;



	if (host->chan_tx || host->chan_rx) {

	if ((host->chan_tx || host->chan_rx) && !host->force_pio) {

		pr_err("PIO IRQ in DMA mode!\n");

		return;

	} else if (!data) {
@@ -551,15 +556,11 @@ static void tmio_mmc_do_data_irq(struct tmio_mmc_host *host) 
	 */



	if (data->flags & MMC_DATA_READ) {

		if (!host->chan_rx)

			disable_mmc_irqs(host, TMIO_MASK_READOP);

		else

		if (host->chan_rx && !host->force_pio)

			tmio_check_bounce_buffer(host);

		dev_dbg(&host->pdev->dev, "Complete Rx request %p\n",

			host->mrq);

	} else {

		if (!host->chan_tx)

			disable_mmc_irqs(host, TMIO_MASK_WRITEOP);

		dev_dbg(&host->pdev->dev, "Complete Tx request %p\n",

			host->mrq);

	}
@@ -583,7 +584,7 @@ static void tmio_mmc_data_irq(struct tmio_mmc_host *host) 
	if (!data)

		goto out;



	if (host->chan_tx && (data->flags & MMC_DATA_WRITE)) {

	if (host->chan_tx && (data->flags & MMC_DATA_WRITE) && !host->force_pio) {

		/*

		 * Has all data been written out yet? Testing on SuperH showed,

		 * that in most cases the first interrupt comes already with the
@@ -596,11 +597,12 @@ static void tmio_mmc_data_irq(struct tmio_mmc_host *host) 
			disable_mmc_irqs(host, TMIO_STAT_DATAEND);

			tasklet_schedule(&host->dma_complete);

		}

	} else if (host->chan_rx && (data->flags & MMC_DATA_READ)) {

	} else if (host->chan_rx && (data->flags & MMC_DATA_READ) && !host->force_pio) {

		disable_mmc_irqs(host, TMIO_STAT_DATAEND);

		tasklet_schedule(&host->dma_complete);

	} else {

		tmio_mmc_do_data_irq(host);

		disable_mmc_irqs(host, TMIO_MASK_READOP | TMIO_MASK_WRITEOP);

	}

out:

	spin_unlock(&host->lock);
@@ -649,12 +651,12 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host, 
	 */

	if (host->data && !cmd->error) {

		if (host->data->flags & MMC_DATA_READ) {

			if (!host->chan_rx)

			if (host->force_pio || !host->chan_rx)

				enable_mmc_irqs(host, TMIO_MASK_READOP);

			else

				tasklet_schedule(&host->dma_issue);

		} else {

			if (!host->chan_tx)

			if (host->force_pio || !host->chan_tx)

				enable_mmc_irqs(host, TMIO_MASK_WRITEOP);

			else

				tasklet_schedule(&host->dma_issue);
@@ -810,6 +812,11 @@ static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host) 
		goto pio;

	}



	if (sg->length < TMIO_MIN_DMA_LEN) {

		host->force_pio = true;

		return;

	}



	disable_mmc_irqs(host, TMIO_STAT_RXRDY);



	/* The only sg element can be unaligned, use our bounce buffer then */
@@ -878,6 +885,11 @@ static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host) 
		goto pio;

	}



	if (sg->length < TMIO_MIN_DMA_LEN) {

		host->force_pio = true;

		return;

	}



	disable_mmc_irqs(host, TMIO_STAT_TXRQ);



	/* The only sg element can be unaligned, use our bounce buffer then */
@@ -1119,6 +1131,7 @@ static void tmio_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq) 


fail:

	host->mrq = NULL;

	host->force_pio = false;

	mrq->cmd->error = ret;

	mmc_request_done(mmc, mrq);

}