Re: [PATCH v3 1/2] tpm_tis_spi: Use DMA-safe memory for SPI transfers

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Thu, Aug 24, 2017 at 10:27:44AM +0200, Alexander Steffen wrote:
> The buffers used as tx_buf/rx_buf in a SPI transfer need to be DMA-safe.
> This cannot be guaranteed for the buffers passed to tpm_tis_spi_read_bytes
> and tpm_tis_spi_write_bytes. Therefore, we need to use our own DMA-safe
> buffer and copy the data to/from it.
> 
> The buffer needs to be allocated separately, to ensure that it is
> cacheline-aligned and not shared with other data, so that DMA can work
> correctly.
> 
> Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
> ---
>  drivers/char/tpm/tpm_tis_spi.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index 88fe72a..05ce841 100644
> --- a/drivers/char/tpm/tpm_tis_spi.c
> +++ b/drivers/char/tpm/tpm_tis_spi.c
> @@ -47,8 +47,8 @@ struct tpm_tis_spi_phy {
>  	struct tpm_tis_data priv;
>  	struct spi_device *spi_device;
>  
> -	u8 tx_buf[4];
> -	u8 rx_buf[4];
> +	u8 *tx_buf;
> +	u8 *rx_buf;
>  };
>  
>  static inline struct tpm_tis_spi_phy *to_tpm_tis_spi_phy(struct tpm_tis_data *data)
> @@ -115,10 +115,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
>  
>  		if (direction) {
>  			spi_xfer.tx_buf = NULL;
> -			spi_xfer.rx_buf = buffer;
>  		} else {
> -			spi_xfer.tx_buf = buffer;
>  			spi_xfer.rx_buf = NULL;
> +			memcpy(phy->tx_buf, buffer, transfer_len);
>  		}
>  
>  		spi_message_init(&m);
> @@ -127,6 +126,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
>  		if (ret < 0)
>  			goto exit;
>  
> +		if (direction)
> +			memcpy(buffer, phy->rx_buf, transfer_len);
> +
>  		len -= transfer_len;
>  		buffer += transfer_len;
>  	}
> @@ -194,6 +196,14 @@ static int tpm_tis_spi_probe(struct spi_device *dev)
>  
>  	phy->spi_device = dev;
>  
> +	phy->tx_buf = devm_kmalloc(&dev->dev, MAX_SPI_FRAMESIZE, GFP_KERNEL);
> +	if (!phy->tx_buf)
> +		return -ENOMEM;
> +
> +	phy->rx_buf = devm_kmalloc(&dev->dev, MAX_SPI_FRAMESIZE, GFP_KERNEL);
> +	if (!phy->rx_buf)
> +		return -ENOMEM;
> +
>  	return tpm_tis_core_init(&dev->dev, &phy->priv, -1, &tpm_spi_phy_ops,
>  				 NULL);
>  }
> -- 
> 2.7.4
> 

Great. This is much less confusing patch for backporting.

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko