linux-kernel - Re: [PATCH 04/12] i2c: qup: schedule EOT and FLUSH tags at the end of transfer

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Message-ID: <20180227223654.GE20901@hector.attlocal.net>
Date:   Tue, 27 Feb 2018 16:36:54 -0600
From:   Andy Gross <andy.gross@...aro.org>
To:     Abhishek Sahu <absahu@...eaurora.org>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        David Brown <david.brown@...aro.org>,
        Sricharan R <sricharan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] i2c: qup: schedule EOT and FLUSH tags at the end
 of transfer

On Sat, Feb 03, 2018 at 01:28:09PM +0530, Abhishek Sahu wrote:
> A single BAM transfer can have multiple read and write messages.
> The EOT and FLUSH tags should be scheduled at the end of BAM HW
> descriptors. Since the READ and WRITE can be present in any order
> so for some of the cases, these tags are not being written
> correctly.
> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>  drivers/i2c/busses/i2c-qup.c | 54 ++++++++++++++++++++------------------------
>  1 file changed, 24 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
> index bb83a2967..6357aff 100644
> --- a/drivers/i2c/busses/i2c-qup.c
> +++ b/drivers/i2c/busses/i2c-qup.c
> @@ -560,7 +560,7 @@ static int qup_i2c_set_tags_smb(u16 addr, u8 *tags, struct qup_i2c_dev *qup,
>  }
>  
>  static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
> -			    struct i2c_msg *msg,  int is_dma)
> +			    struct i2c_msg *msg)
>  {
>  	u16 addr = i2c_8bit_addr_from_msg(msg);
>  	int len = 0;
> @@ -601,11 +601,6 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
>  	else
>  		tags[len++] = data_len;
>  
> -	if ((msg->flags & I2C_M_RD) && last && is_dma) {
> -		tags[len++] = QUP_BAM_INPUT_EOT;
> -		tags[len++] = QUP_BAM_FLUSH_STOP;
> -	}
> -

So lets say you have multiple read and 1 write message.  These changes will send
a EOT/FLUSH for all reads.  I think the intent here was that the last read
message (not the last message) would have the EOT+FLUSH.  Can there be an issue
with sending EOT/FLUSH for all reads?  And how does this mesh up with the BAM
signaling?


Regards,

Andy