Re: [PATCH v2 2/8] spi: imx: replace fixed timeout with calculated one

[Robin Gong <b38343@freescale.com>]

On Fri, Sep 25, 2015 at 07:57:09PM +0200, Anton Bondarenko wrote:
> Fixed timeout value can fire while transaction is ongoing. This may happen
> because there are no strict requirements on SPI transaction duration.
> Dynamic timeout value is generated based on SCLK and transaction size.
> 
> There is also 4 * SCLK delay between TX bursts related to CS change.
> 
> Signed-off-by: Anton Bondarenko <anton_bondarenko@mentor.com>
> ---
>  drivers/spi/spi-imx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 41 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
> index 165bc2c..6c98eda 100644
> --- a/drivers/spi/spi-imx.c
> +++ b/drivers/spi/spi-imx.c
> @@ -59,7 +59,6 @@
>  
>  /* The maximum  bytes that a sdma BD can transfer.*/
>  #define MAX_SDMA_BD_BYTES  (1 << 15)
> -#define IMX_DMA_TIMEOUT (msecs_to_jiffies(3000))
>  struct spi_imx_config {
>  	unsigned int speed_hz;
>  	unsigned int bpw;
> @@ -95,6 +94,7 @@ struct spi_imx_data {
>  	struct clk *clk_per;
>  	struct clk *clk_ipg;
>  	unsigned long spi_clk;
> +	unsigned int spi_bus_clk;
>  
>  	unsigned int count;
>  	void (*tx)(struct spi_imx_data *);
> @@ -317,8 +317,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
>  {
>  	u32 ctrl = MX51_ECSPI_CTRL_ENABLE, dma = 0;
>  	u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG);
> -
> -	u32 clk = config->speed_hz, delay;
> +	u32 delay;
>  
>  	/*
>  	 * The hardware seems to have a race condition when changing modes. The
> @@ -330,7 +329,9 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
>  	ctrl |= MX51_ECSPI_CTRL_MODE_MASK;
>  
>  	/* set clock speed */
> -	ctrl |= mx51_ecspi_clkdiv(spi_imx->spi_clk, config->speed_hz, &clk);
> +	spi_imx->spi_bus_clk = config->speed_hz;
> +	ctrl |= mx51_ecspi_clkdiv(spi_imx->spi_clk, config->speed_hz,
> +				  &spi_imx->spi_bus_clk);
>  
>  	/* set chip select to use */
>  	ctrl |= MX51_ECSPI_CTRL_CS(config->cs);
> @@ -363,7 +364,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
>  	 * the SPI communication as the device on the other end would consider
>  	 * the change of SCLK polarity as a clock tick already.
>  	 */
> -	delay = (2 * 1000000) / clk;
> +	delay = (2 * USEC_PER_SEC) / spi_imx->spi_bus_clk;
>  	if (likely(delay < 10))	/* SCLK is faster than 100 kHz */
>  		udelay(delay);
>  	else			/* SCLK is _very_ slow */
> @@ -889,12 +890,40 @@ static void spi_imx_dma_tx_callback(void *cookie)
>  	complete(&spi_imx->dma_tx_completion);
>  }
>  
> +static int spi_imx_calculate_timeout(struct spi_imx_data *spi_imx, int size)
> +{
> +	unsigned long coef1 = 1;
> +	unsigned long coef2 = MSEC_PER_SEC;
> +	unsigned long timeout = 0;
> +
> +	/* Swap coeficients to avoid div by 0 */
> +	if (spi_imx->spi_bus_clk < MSEC_PER_SEC) {
> +		coef1 = MSEC_PER_SEC;
> +		coef2 = 1;
> +	}
> +
> +	/* Time with actual data transfer */
> +	timeout += DIV_ROUND_UP(8 * size * coef1,
> +				spi_imx->spi_bus_clk / coef2);
> +
> +	/* Take CS change delay related to HW */
> +	timeout += DIV_ROUND_UP((size - 1) * 4 * coef1,
> +				spi_imx->spi_bus_clk / coef2);
> +
> +	/* Add extra second for scheduler related activities */
> +	timeout += MSEC_PER_SEC;
> +
> +	/* Double calculated timeout */
> +	return msecs_to_jiffies(2 * timeout);
> +}
> +
>  static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>  				struct spi_transfer *transfer)
>  {
>  	struct dma_async_tx_descriptor *desc_tx = NULL, *desc_rx = NULL;
>  	int ret;
>  	unsigned long timeout;
> +	unsigned long transfer_timeout;
>  	const int left = transfer->len % spi_imx->wml;
>  	struct spi_master *master = spi_imx->bitbang.master;
>  	struct sg_table *tx = &transfer->tx_sg, *rx = &transfer->rx_sg;
> @@ -947,9 +976,11 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>  	dma_async_issue_pending(master->dma_tx);
>  	spi_imx->devtype_data->trigger(spi_imx);
>  
> +	transfer_timeout = spi_imx_calculate_timeout(spi_imx, transfer->len);
> +
>  	/* Wait SDMA to finish the data transfer.*/
>  	timeout = wait_for_completion_timeout(&spi_imx->dma_tx_completion,
> -						IMX_DMA_TIMEOUT);
> +						transfer_timeout);
>  	if (!timeout) {
>  		pr_warn("%s %s: I/O Error in DMA TX\n",
>  			dev_driver_string(&master->dev),
> @@ -957,8 +988,10 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>  		dmaengine_terminate_all(master->dma_tx);
>  		dmaengine_terminate_all(master->dma_rx);
>  	} else {
> +		transfer_timeout = spi_imx_calculate_timeout(spi_imx,
> +							     spi_imx->wml * 2);
*2 again here? Although spi_imx_calculate_timeout has double it.
>  		timeout = wait_for_completion_timeout(
> -				&spi_imx->dma_rx_completion, IMX_DMA_TIMEOUT);
> +				&spi_imx->dma_rx_completion, transfer_timeout);
>  		if (!timeout) {
>  			pr_warn("%s %s: I/O Error in DMA RX\n",
>  				dev_driver_string(&master->dev),
> @@ -980,7 +1013,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
>  			spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TCEN);
>  
>  			timeout = wait_for_completion_timeout(
> -					&spi_imx->xfer_done, IMX_DMA_TIMEOUT);
> +					&spi_imx->xfer_done, transfer_timeout);
>  			if (!timeout) {
>  				pr_warn("%s %s: I/O Error in RX tail\n",
>  					dev_driver_string(&master->dev),
> -- 
> 2.5.2
>