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Date: Thu, 20 Aug 2015 16:56:56 +0200
From: Maxime Ripard <maxime.ripard@...e-electrons.com>
To: Michal Suchanek <hramrach@...il.com>
Cc: linux-sunxi@...glegroups.com, Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Russell King <linux@....linux.org.uk>,
Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-spi@...r.kernel.org,
Emilio López <emilio@...pez.com.ar>
Subject: Re: [PATCH 4/9] spi: sun4i: add DMA support
On Thu, Aug 20, 2015 at 02:19:46PM -0000, Emilio López wrote:
> From: Emilio López <emilio@...pez.com.ar>
>
> This patch adds support for 64 byte or bigger transfers on the
> sun4i SPI controller. Said transfers will be performed via DMA.
>
> Signed-off-by: Emilio López <emilio@...pez.com.ar>
> Tested-by: Michal Suchanek <hramrach@...il.com>
This should have your SoB.
> ---
> drivers/spi/spi-sun4i.c | 145 +++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 130 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
> index 4dda366..63242a7 100644
> --- a/drivers/spi/spi-sun4i.c
> +++ b/drivers/spi/spi-sun4i.c
> @@ -14,6 +14,8 @@
> #include <linux/clk.h>
> #include <linux/delay.h>
> #include <linux/device.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> #include <linux/interrupt.h>
> #include <linux/io.h>
> #include <linux/module.h>
> @@ -34,6 +36,7 @@
> #define SUN4I_CTL_CPHA BIT(2)
> #define SUN4I_CTL_CPOL BIT(3)
> #define SUN4I_CTL_CS_ACTIVE_LOW BIT(4)
> +#define SUN4I_CTL_DMAMC_DEDICATED BIT(5)
> #define SUN4I_CTL_LMTF BIT(6)
> #define SUN4I_CTL_TF_RST BIT(8)
> #define SUN4I_CTL_RF_RST BIT(9)
> @@ -51,6 +54,8 @@
> #define SUN4I_INT_STA_REG 0x10
>
> #define SUN4I_DMA_CTL_REG 0x14
> +#define SUN4I_DMA_CTL_RF_READY BIT(0)
> +#define SUN4I_DMA_CTL_TF_NOT_FULL BIT(10)
>
> #define SUN4I_WAIT_REG 0x18
>
> @@ -130,6 +135,13 @@ static inline void sun4i_spi_fill_fifo(struct sun4i_spi *sspi, int len)
> }
> }
>
> +static bool sun4i_spi_can_dma(struct spi_master *master,
> + struct spi_device *spi,
> + struct spi_transfer *tfr)
> +{
> + return tfr->len >= SUN4I_FIFO_DEPTH;
> +}
> +
> static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
> {
> struct sun4i_spi *sspi = spi_master_get_devdata(spi->master);
> @@ -169,17 +181,12 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
> struct spi_transfer *tfr)
> {
> struct sun4i_spi *sspi = spi_master_get_devdata(master);
> + struct dma_async_tx_descriptor *desc_tx = NULL, *desc_rx = NULL;
> unsigned int speed, mclk_rate, div, timeout;
> unsigned int start, end, tx_time;
> unsigned int tx_len = 0;
> + u32 reg, trigger = 0;
> int ret = 0;
> - u32 reg;
> -
> - /* We don't support transfer larger than the FIFO */
> - if (tfr->len > SUN4I_FIFO_DEPTH)
> - return -EINVAL;
> - if (tfr->tx_buf && tfr->len => SUN4I_FIFO_DEPTH)
> - return -EINVAL;
>
> reinit_completion(&sspi->done);
> sspi->tx_buf = tfr->tx_buf;
> @@ -277,14 +284,67 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
> sun4i_spi_write(sspi, SUN4I_BURST_CNT_REG, SUN4I_BURST_CNT(tfr->len));
> sun4i_spi_write(sspi, SUN4I_XMIT_CNT_REG, SUN4I_XMIT_CNT(tx_len));
>
> - /* Fill the TX FIFO */
> - /* Filling the fifo fully causes timeout for some reason
> - * at least on spi2 on a10s */
> - sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH - 1);
> -
> /* Enable the interrupts */
> sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC);
>
> + if (sun4i_spi_can_dma(master, spi, tfr)) {
> + dev_dbg(&sspi->master->dev, "Using DMA mode for transfer\n");
> +
> + if (sspi->tx_buf) {
> + desc_tx = dmaengine_prep_slave_sg(master->dma_tx,
> + tfr->tx_sg.sgl, tfr->tx_sg.nents,
> + DMA_TO_DEVICE,
> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> + if (!desc_tx) {
> + dev_err(&sspi->master->dev,
> + "Couldn't prepare dma slave\n");
> + return -EIO;
> + }
> +
> + trigger |= SUN4I_DMA_CTL_TF_NOT_FULL;
> +
> + dmaengine_submit(desc_tx);
> + dma_async_issue_pending(master->dma_tx);
> +
> + }
> +
> + if (sspi->rx_buf) {
> + desc_rx = dmaengine_prep_slave_sg(master->dma_rx,
> + tfr->rx_sg.sgl, tfr->rx_sg.nents,
> + DMA_FROM_DEVICE,
> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> + if (!desc_rx) {
> + dev_err(&sspi->master->dev,
> + "Couldn't prepare dma slave\n");
> + return -EIO;
> + }
> +
> + trigger |= SUN4I_DMA_CTL_RF_READY;
> +
> + dmaengine_submit(desc_rx);
> + dma_async_issue_pending(master->dma_rx);
> + }
What happens if the dma driver controller isn't present in your
system? Or that it doesn't have any channels available anymore?
> + /* Enable Dedicated DMA requests */
> + reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
> + reg |= SUN4I_CTL_DMAMC_DEDICATED;
> + sun4i_spi_write(sspi, SUN4I_CTL_REG, reg);
> + sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, trigger);
> + } else {
> + dev_dbg(&sspi->master->dev, "Using PIO mode for transfer\n");
> +
> + /* Disable DMA requests */
> + reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
> + sun4i_spi_write(sspi, SUN4I_CTL_REG,
> + reg & ~SUN4I_CTL_DMAMC_DEDICATED);
> + sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, 0);
> +
> + /* Fill the TX FIFO */
> + /* Filling the fifo fully causes timeout for some reason
> + * at least on spi2 on a10s */
> + sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH - 1);
> + }
> +
> /* Start the transfer */
> reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
> sun4i_spi_write(sspi, SUN4I_CTL_REG, reg | SUN4I_CTL_XCH);
> @@ -303,7 +363,12 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
> goto out;
> }
>
> - sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
> + if (sun4i_spi_can_dma(master, spi, tfr) && desc_rx) {
> + /* The receive transfer should be the last one to finish */
> + dma_wait_for_async_tx(desc_rx);
Nope, this is only meant for async_tx. You should register a callback
in your transfer that will mark the completion structure as completed,
and then drain the FIFO only if not using DMA.
> + } else {
> + sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
> + }
>
> out:
> sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
> @@ -368,6 +433,7 @@ static int sun4i_spi_runtime_suspend(struct device *dev)
>
> static int sun4i_spi_probe(struct platform_device *pdev)
> {
> + struct dma_slave_config dma_sconfig;
> struct spi_master *master;
> struct sun4i_spi *sspi;
> struct resource *res;
> @@ -403,7 +469,9 @@ static int sun4i_spi_probe(struct platform_device *pdev)
> goto err_free_master;
> }
>
> + init_completion(&sspi->done);
> sspi->master = master;
> + master->can_dma = sun4i_spi_can_dma;
> master->set_cs = sun4i_spi_set_cs;
> master->transfer_one = sun4i_spi_transfer_one;
> master->num_chipselect = 4;
> @@ -426,7 +494,45 @@ static int sun4i_spi_probe(struct platform_device *pdev)
> goto err_free_master;
> }
>
> - init_completion(&sspi->done);
> + master->dma_tx = dma_request_slave_channel_reason(&pdev->dev, "tx");
> + if (IS_ERR(master->dma_tx)) {
> + dev_err(&pdev->dev, "Unable to acquire DMA channel TX\n");
> + ret = PTR_ERR(master->dma_tx);
> + goto err_free_master;
> + }
> +
> + dma_sconfig.direction = DMA_MEM_TO_DEV;
> + dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> + dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> + dma_sconfig.dst_addr = res->start + SUN4I_TXDATA_REG;
> + dma_sconfig.src_maxburst = 1;
> + dma_sconfig.dst_maxburst = 1;
> +
> + ret = dmaengine_slave_config(master->dma_tx, &dma_sconfig);
> + if (ret) {
> + dev_err(&pdev->dev, "Unable to configure TX DMA slave\n");
> + goto err_tx_dma_release;
> + }
> +
> + master->dma_rx = dma_request_slave_channel_reason(&pdev->dev, "rx");
> + if (IS_ERR(master->dma_rx)) {
> + dev_err(&pdev->dev, "Unable to acquire DMA channel RX\n");
> + ret = PTR_ERR(master->dma_rx);
> + goto err_tx_dma_release;
> + }
> +
> + dma_sconfig.direction = DMA_DEV_TO_MEM;
> + dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> + dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> + dma_sconfig.src_addr = res->start + SUN4I_RXDATA_REG;
> + dma_sconfig.src_maxburst = 1;
> + dma_sconfig.dst_maxburst = 1;
We can't use a higher bust size?
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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