Re: [alsa-devel] [PATCH] dma: add new DMA control commands

On Thu, 2012-10-18 at 13:32 +0800, Huang Shijie wrote:

From: Huang Shijie shijie8@gmail.com

[1] Why add these new DMA control commands? In mx6q, the gpmi-nand driver is the only user of the APBH-DMA. The dma clock is enabled when we have successfully requested a DMA channel. So even when the gpmi-nand driver does not work, the dma clock(apbh-dma) still runs in high speed (198MHz). To save some power, it is better to disable the dma clock when the dma device, such as gpmi-nand, is not working anymore. When the dma device becomes work again, enable the dma clock again.

[2] add new DMA control commands: DMA_START/DMA_END DMA_START: do some preprations to start the DMA engine, such as enable the necessary clocks. DMA_END: do some works to end the DMA engine, such as disable the necessary clocks.

[3] This patch does not change any logic in i2c-mxs driver and mxs-pcm driver. But for gpmi-nand driver, we will enable the the clock only when we select the nand chip, and want to do some real jobs with the nand chip. For mxs-mmc driver, disable the dma clock in the suspend; and enable the dma clock in the resume.

Why cant you do start (prepare clock etc) when you submit the descriptor to dmaengine. Can be done in tx_submit callback. Similarly remove the clock when dma transaction gets completed.

I don't think we need a new API for this, it needs to be handled by driver on its own.

Signed-off-by: Huang Shijie b32955@freescale.com

drivers/dma/mxs-dma.c | 17 +++++++++++++++++ drivers/i2c/busses/i2c-mxs.c | 10 +++++++++- drivers/mmc/host/mxs-mmc.c | 19 ++++++++++++++++--- drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 10 ++++++++++ drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 10 ++++++---- include/linux/dmaengine.h | 6 ++++++ sound/soc/mxs/mxs-pcm.c | 12 ++++++++++++ 7 files changed, 76 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c index 9f02e79..89286f4 100644 --- a/drivers/dma/mxs-dma.c +++ b/drivers/dma/mxs-dma.c @@ -384,6 +384,8 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan) /* the descriptor is ready */ async_tx_ack(&mxs_chan->desc);

• clk_disable_unprepare(mxs_dma->clk);
• return 0;

err_clk: @@ -399,6 +401,14 @@ static void mxs_dma_free_chan_resources(struct dma_chan *chan) { struct mxs_dma_chan *mxs_chan = to_mxs_dma_chan(chan); struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;

• int ret;

• ret = clk_prepare_enable(mxs_dma->clk);

• if (ret) {

• dev_err(mxs_dma->dma_device.dev,
  

• 	"failed in enabling the dma clock\n");
  

• return;
  

• }

  mxs_dma_disable_chan(mxs_chan);

@@ -597,9 +607,13 @@ static int mxs_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned long arg) { struct mxs_dma_chan *mxs_chan = to_mxs_dma_chan(chan);

• struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma; int ret = 0;

  switch (cmd) {

• case DMA_START:

• ret = clk_prepare_enable(mxs_dma->clk);
  

• break;
  

  case DMA_TERMINATE_ALL: mxs_dma_reset_chan(mxs_chan); mxs_dma_disable_chan(mxs_chan);

@@ -610,6 +624,9 @@ static int mxs_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, case DMA_RESUME: mxs_dma_resume_chan(mxs_chan); break;

• case DMA_END:

• clk_disable_unprepare(mxs_dma->clk);
  

• break;
  

  default: ret = -ENOSYS; }

diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c index 1f58197..da1e881 100644 --- a/drivers/i2c/busses/i2c-mxs.c +++ b/drivers/i2c/busses/i2c-mxs.c @@ -643,6 +643,12 @@ static int __devinit mxs_i2c_probe(struct platform_device *pdev) dev_err(dev, "Failed to request dma\n"); return -ENODEV; }

• err = dmaengine_device_control(i2c->dmach, DMA_START, 0);
  

• if (err) {
  

• 	dma_release_channel(i2c->dmach);
  

• 	dev_err(dev, "Failed to start dma\n");
  

• 	return err;
  

• }
  

  }

  platform_set_drvdata(pdev, i2c);

@@ -680,8 +686,10 @@ static int __devexit mxs_i2c_remove(struct platform_device *pdev) if (ret) return -EBUSY;

• if (i2c->dmach)

• if (i2c->dmach) {

• dmaengine_device_control(i2c->dmach, DMA_END, 0);
  

  dma_release_channel(i2c->dmach);

• }

  writel(MXS_I2C_CTRL0_SFTRST, i2c->regs + MXS_I2C_CTRL0_SET);

diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c index 80d1e6d..aa91830 100644 --- a/drivers/mmc/host/mxs-mmc.c +++ b/drivers/mmc/host/mxs-mmc.c @@ -676,6 +676,9 @@ static int mxs_mmc_probe(struct platform_device *pdev) "%s: failed to request dma\n", __func__); goto out_clk_put; }

• ret = dmaengine_device_control(ssp->dmach, DMA_START, 0);

• if (ret)

• goto out_free_dma;
  
  

  /* set mmc core parameters */ mmc->ops = &mxs_mmc_ops;

@@ -717,18 +720,20 @@ static int mxs_mmc_probe(struct platform_device *pdev) ret = devm_request_irq(&pdev->dev, irq_err, mxs_mmc_irq_handler, 0, DRIVER_NAME, host); if (ret)

• goto out_free_dma;
  

• goto out_end_free_dma;
  
  

  spin_lock_init(&host->lock);

  ret = mmc_add_host(mmc); if (ret)

• goto out_free_dma;
  

• goto out_end_free_dma;
  
  

  dev_info(mmc_dev(host->mmc), "initialized\n");

  return 0;

+out_end_free_dma:

• dmaengine_device_control(ssp->dmach, DMA_END, 0);

out_free_dma: if (ssp->dmach) dma_release_channel(ssp->dmach); @@ -750,8 +755,10 @@ static int mxs_mmc_remove(struct platform_device *pdev)

platform_set_drvdata(pdev, NULL);

• if (ssp->dmach)

• if (ssp->dmach) {

• dmaengine_device_control(ssp->dmach, DMA_END, 0);
  

  dma_release_channel(ssp->dmach);

• }

  clk_disable_unprepare(ssp->clk); clk_put(ssp->clk);

@@ -772,6 +779,7 @@ static int mxs_mmc_suspend(struct device *dev) ret = mmc_suspend_host(mmc);

clk_disable_unprepare(ssp->clk);

• dmaengine_device_control(ssp->dmach, DMA_END, 0);

  return ret;

} @@ -784,8 +792,13 @@ static int mxs_mmc_resume(struct device *dev) int ret = 0;

clk_prepare_enable(ssp->clk);

• ret = dmaengine_device_control(ssp->dmach, DMA_START, 0);

• if (ret)

• return ret;
  
  

  ret = mmc_resume_host(mmc);

• if (ret)

• dmaengine_device_control(ssp->dmach, DMA_END, 0);
  
  

  return ret;

} diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c index 3502acc..20ed3f3 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c @@ -958,6 +958,7 @@ void gpmi_begin(struct gpmi_nand_data *this) uint32_t reg; unsigned int dll_wait_time_in_us; struct gpmi_nfc_hardware_timing hw;

• struct dma_chan *channel = get_dma_chan(this); int ret;

  /* Enable the clock. */

@@ -967,6 +968,12 @@ void gpmi_begin(struct gpmi_nand_data *this) goto err_out; }

• ret = dmaengine_device_control(channel, DMA_START, 0);
• if (ret) {

• gpmi_disable_clk(this);
  

• goto err_out;
  

• }
• /* Only initialize the timing once */ if (this->flags & GPMI_TIMING_INIT_OK) return;

@@ -1035,7 +1042,10 @@ err_out:

void gpmi_end(struct gpmi_nand_data *this) {

• struct dma_chan *channel = get_dma_chan(this);
• gpmi_disable_clk(this);
• dmaengine_device_control(channel, DMA_END, 0);

}

/* Clears a BCH interrupt. */ diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c index e2c56fc..5694d03 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c @@ -815,12 +815,14 @@ static void gpmi_select_chip(struct mtd_info *mtd, int chipnr) struct nand_chip *chip = mtd->priv; struct gpmi_nand_data *this = chip->priv;

• if ((this->current_chip < 0) && (chipnr >= 0))

• if ((this->current_chip < 0) && (chipnr >= 0)) {

• /* set the current_chip before we call gpmi_begin(). */
  

• this->current_chip = chipnr;
  

  gpmi_begin(this);

• else if ((this->current_chip >= 0) && (chipnr < 0))

• } else if ((this->current_chip >= 0) && (chipnr < 0)) { gpmi_end(this);

• this->current_chip = chipnr;

• this->current_chip = chipnr;
  

• }

}

static void gpmi_read_buf(struct mtd_info *mtd, uint8_t *buf, int len) diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index d3201e4..79f864a 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -199,6 +199,8 @@ enum dma_ctrl_flags { /**

• enum dma_ctrl_cmd - DMA operations that can optionally be exercised
• on a running channel.

• • @DMA_START: do some preprations to start the DMA engine, such as enable the
• • necessary clocks.
  • @DMA_TERMINATE_ALL: terminate all ongoing transfers
  • @DMA_PAUSE: pause ongoing transfers
  • @DMA_RESUME: resume paused transfer

@@ -209,13 +211,17 @@ enum dma_ctrl_flags {

• command.
• @FSLDMA_EXTERNAL_START: this command will put the Freescale DMA controller
• into external start mode.

• • @DMA_END: do some works to end the DMA engine, such as disable the
• • necessary clocks.
  */

enum dma_ctrl_cmd {

• DMA_START, DMA_TERMINATE_ALL, DMA_PAUSE, DMA_RESUME, DMA_SLAVE_CONFIG, FSLDMA_EXTERNAL_START,
• DMA_END,

};

/** diff --git a/sound/soc/mxs/mxs-pcm.c b/sound/soc/mxs/mxs-pcm.c index f82d766..cfcc30f 100644 --- a/sound/soc/mxs/mxs-pcm.c +++ b/sound/soc/mxs/mxs-pcm.c @@ -92,6 +92,7 @@ static int snd_mxs_open(struct snd_pcm_substream *substream) { struct snd_soc_pcm_runtime *rtd = substream->private_data; struct mxs_pcm_dma_data *pcm_dma_data;

• struct dma_chan *chan; int ret;

  pcm_dma_data = kzalloc(sizeof(*pcm_dma_data), GFP_KERNEL);

@@ -107,6 +108,14 @@ static int snd_mxs_open(struct snd_pcm_substream *substream) return ret; }

• chan = snd_dmaengine_pcm_get_chan(substream);

• ret = dmaengine_device_control(chan, DMA_START, (unsigned long)0);

• if (ret) {

• snd_dmaengine_pcm_close(substream);
  

• kfree(pcm_dma_data);
  

• return ret;
  

• }

• snd_soc_set_runtime_hwparams(substream, &snd_mxs_hardware);

  snd_dmaengine_pcm_set_data(substream, pcm_dma_data);

@@ -117,7 +126,10 @@ static int snd_mxs_open(struct snd_pcm_substream *substream) static int snd_mxs_close(struct snd_pcm_substream *substream) { struct mxs_pcm_dma_data *pcm_dma_data = snd_dmaengine_pcm_get_data(substream);

• struct dma_chan *chan;

• chan = snd_dmaengine_pcm_get_chan(substream);

• dmaengine_device_control(chan, DMA_END, 0); snd_dmaengine_pcm_close(substream); kfree(pcm_dma_data);