[v7,8/8] bus: mhi: core: Ensure non-zero session or sequence ID values are used

While writing any sequence or session identifiers, it is possible that
the host could write a zero value, whereas only non-zero values should
be supported writes to those registers. Ensure that the host does not
write a non-zero value for them and also log them in debug messages. A
macro is introduced to simplify this check and the existing checks are
also converted to use this macro.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>
---
 drivers/bus/mhi/core/boot.c     | 15 +++++++--------
 drivers/bus/mhi/core/internal.h |  1 +
 2 files changed, 8 insertions(+), 8 deletions(-)

On Fri, May 08, 2020 at 07:26:48PM -0700, Bhaumik Bhatt wrote:
> While writing any sequence or session identifiers, it is possible that
> the host could write a zero value, whereas only non-zero values should
> be supported writes to those registers. Ensure that the host does not
> write a non-zero value for them and also log them in debug messages. A
> macro is introduced to simplify this check and the existing checks are
> also converted to use this macro.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/boot.c     | 15 +++++++--------
>  drivers/bus/mhi/core/internal.h |  1 +
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/boot.c b/drivers/bus/mhi/core/boot.c
> index 80e4d76..0b38014 100644
> --- a/drivers/bus/mhi/core/boot.c
> +++ b/drivers/bus/mhi/core/boot.c
> @@ -43,10 +43,7 @@ void mhi_rddm_prepare(struct mhi_controller *mhi_cntrl,
>  		      lower_32_bits(mhi_buf->dma_addr));
>  
>  	mhi_write_reg(mhi_cntrl, base, BHIE_RXVECSIZE_OFFS, mhi_buf->len);
> -	sequence_id = prandom_u32() & BHIE_RXVECSTATUS_SEQNUM_BMSK;
> -
> -	if (unlikely(!sequence_id))
> -		sequence_id = 1;
> +	sequence_id = MHI_RANDOM_U32_NONZERO(BHIE_RXVECSTATUS_SEQNUM_BMSK);
>  
>  	mhi_write_reg_field(mhi_cntrl, base, BHIE_RXVECDB_OFFS,
>  			    BHIE_RXVECDB_SEQNUM_BMSK, BHIE_RXVECDB_SEQNUM_SHFT,
> @@ -189,7 +186,9 @@ static int mhi_fw_load_amss(struct mhi_controller *mhi_cntrl,
>  		return -EIO;
>  	}
>  
> -	dev_dbg(dev, "Starting AMSS download via BHIe\n");
> +	sequence_id = MHI_RANDOM_U32_NONZERO(BHIE_TXVECSTATUS_SEQNUM_BMSK);
> +	dev_dbg(dev, "Starting AMSS download via BHIe. Sequence ID:%u\n",
> +		sequence_id);
>  	mhi_write_reg(mhi_cntrl, base, BHIE_TXVECADDR_HIGH_OFFS,
>  		      upper_32_bits(mhi_buf->dma_addr));
>  
> @@ -198,7 +197,6 @@ static int mhi_fw_load_amss(struct mhi_controller *mhi_cntrl,
>  
>  	mhi_write_reg(mhi_cntrl, base, BHIE_TXVECSIZE_OFFS, mhi_buf->len);
>  
> -	sequence_id = prandom_u32() & BHIE_TXVECSTATUS_SEQNUM_BMSK;
>  	mhi_write_reg_field(mhi_cntrl, base, BHIE_TXVECDB_OFFS,
>  			    BHIE_TXVECDB_SEQNUM_BMSK, BHIE_TXVECDB_SEQNUM_SHFT,
>  			    sequence_id);
> @@ -246,14 +244,15 @@ static int mhi_fw_load_sbl(struct mhi_controller *mhi_cntrl,
>  		goto invalid_pm_state;
>  	}
>  
> -	dev_dbg(dev, "Starting SBL download via BHI\n");
> +	session_id = MHI_RANDOM_U32_NONZERO(BHI_TXDB_SEQNUM_BMSK);
> +	dev_dbg(dev, "Starting SBL download via BHI. Session ID:%u\n",
> +		session_id);
>  	mhi_write_reg(mhi_cntrl, base, BHI_STATUS, 0);
>  	mhi_write_reg(mhi_cntrl, base, BHI_IMGADDR_HIGH,
>  		      upper_32_bits(dma_addr));
>  	mhi_write_reg(mhi_cntrl, base, BHI_IMGADDR_LOW,
>  		      lower_32_bits(dma_addr));
>  	mhi_write_reg(mhi_cntrl, base, BHI_IMGSIZE, size);
> -	session_id = prandom_u32() & BHI_TXDB_SEQNUM_BMSK;
>  	mhi_write_reg(mhi_cntrl, base, BHI_IMGTXDB, session_id);
>  	read_unlock_bh(pm_lock);
>  
> diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
> index 0965ca3..80b32c2 100644
> --- a/drivers/bus/mhi/core/internal.h
> +++ b/drivers/bus/mhi/core/internal.h
> @@ -452,6 +452,7 @@ enum mhi_pm_state {
>  #define PRIMARY_CMD_RING		0
>  #define MHI_DEV_WAKE_DB			127
>  #define MHI_MAX_MTU			0xffff
> +#define MHI_RANDOM_U32_NONZERO(bmsk)	(prandom_u32_max(bmsk) + 1)
>  
>  enum mhi_er_type {
>  	MHI_ER_TYPE_INVALID = 0x0,
> -- 
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