On Mon, Mar 7, 2011 at 7:30 AM, Guennadi Liakhovetski
<g.liakhovetski@xxxxxx> wrote:
> 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: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> ---
> drivers/mmc/host/tmio_mmc.c | 33 +++++++++++++++++++++++----------
> 1 files changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/mmc/host/tmio_mmc.c b/drivers/mmc/host/tmio_mmc.c
> index aa384ba..f5ec5e6 100644
> --- a/drivers/mmc/host/tmio_mmc.c
> +++ b/drivers/mmc/host/tmio_mmc.c
> @@ -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;
> @@ -384,6 +387,7 @@ 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);
>
> @@ -403,6 +407,7 @@ 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);
>
> @@ -484,7 +489,7 @@ 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) {
> @@ -550,15 +555,11 @@ 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);
> }
> @@ -582,7 +583,7 @@ 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
> @@ -595,11 +596,12 @@ 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);
> @@ -648,12 +650,12 @@ 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);
> @@ -811,6 +813,11 @@ 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 */
> @@ -886,6 +893,11 @@ 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 */
> @@ -1132,6 +1144,7 @@ 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);
> }
> --
> 1.7.2.3
>
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>
This is probably a good idea for other controllers too, no? I mean to
implement something similar for other controllers...
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