Re: [PATCH] spi/omap2_mcspi: Verify TX reg is empty after TX only xfer with DMA

[Tony Lindgren <tony@atomide.com>]

* Ilkka Koskinen <ilkka.koskinen@nokia.com> [101019 06:55]:
> In case of TX only with DMA, the driver assumes that the data
> has been transferred once DMA callback in invoked. However,
> SPI's shift register may still contain data. Thus, the driver
> is supposed to verify that the register is empty and the end of
> the SPI transfer has been reached.
> 
> Signed-off-by: Ilkka Koskinen <ilkka.koskinen@nokia.com>
> Tested-by: Tuomas Katila <ext-tuomas.2.katila@nokia.com>

Grant, can you please queue this one?

Acked-by: Tony Lindgren <tony@atomide.com>


> ---
>  drivers/spi/omap2_mcspi.c |   39 ++++++++++++++++++++++++++-------------
>  1 files changed, 26 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
> index b3a94ca..a2e053c 100644
> --- a/drivers/spi/omap2_mcspi.c
> +++ b/drivers/spi/omap2_mcspi.c
> @@ -296,6 +296,19 @@ static int omap2_mcspi_enable_clocks(struct omap2_mcspi *mcspi)
>  	return 0;
>  }
>  
> +static int mcspi_wait_for_reg_bit(void __iomem *reg, unsigned long bit)
> +{
> +	unsigned long timeout;
> +
> +	timeout = jiffies + msecs_to_jiffies(1000);
> +	while (!(__raw_readl(reg) & bit)) {
> +		if (time_after(jiffies, timeout))
> +			return -1;
> +		cpu_relax();
> +	}
> +	return 0;
> +}
> +
>  static unsigned
>  omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
>  {
> @@ -309,11 +322,14 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
>  	u32			l;
>  	u8			* rx;
>  	const u8		* tx;
> +	void __iomem		*chstat_reg;
>  
>  	mcspi = spi_master_get_devdata(spi->master);
>  	mcspi_dma = &mcspi->dma_channels[spi->chip_select];
>  	l = mcspi_cached_chconf0(spi);
>  
> +	chstat_reg = cs->base + OMAP2_MCSPI_CHSTAT0;
> +
>  	count = xfer->len;
>  	c = count;
>  	word_len = cs->word_len;
> @@ -382,6 +398,16 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
>  	if (tx != NULL) {
>  		wait_for_completion(&mcspi_dma->dma_tx_completion);
>  		dma_unmap_single(NULL, xfer->tx_dma, count, DMA_TO_DEVICE);
> +
> +		/* for TX_ONLY mode, be sure all words have shifted out */
> +		if (rx == NULL) {
> +			if (mcspi_wait_for_reg_bit(chstat_reg,
> +						OMAP2_MCSPI_CHSTAT_TXS) < 0)
> +				dev_err(&spi->dev, "TXS timed out\n");
> +			else if (mcspi_wait_for_reg_bit(chstat_reg,
> +						OMAP2_MCSPI_CHSTAT_EOT) < 0)
> +				dev_err(&spi->dev, "EOT timed out\n");
> +		}
>  	}
>  
>  	if (rx != NULL) {
> @@ -435,19 +461,6 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
>  	return count;
>  }
>  
> -static int mcspi_wait_for_reg_bit(void __iomem *reg, unsigned long bit)
> -{
> -	unsigned long timeout;
> -
> -	timeout = jiffies + msecs_to_jiffies(1000);
> -	while (!(__raw_readl(reg) & bit)) {
> -		if (time_after(jiffies, timeout))
> -			return -1;
> -		cpu_relax();
> -	}
> -	return 0;
> -}
> -
>  static unsigned
>  omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
>  {
> -- 
> 1.6.0.4
>