linux-kernel - Re: [PATCH v2 1/3] soundwire: qcom: clear BIT FIELDs before value set.

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Date:   Wed, 16 Sep 2020 18:16:34 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     yung-chuan.liao@...ux.intel.com,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] soundwire: qcom: clear BIT FIELDs before value
 set.

Hi Srini,

On 16-09-20, 10:21, Srinivas Kandagatla wrote:
> According to usage (bitfields.h) of REG_FIELDS,
> Modify is:
>   reg &= ~REG_FIELD_C;
>   reg |= FIELD_PREP(REG_FIELD_C, c);
> 
> Patch ("soundwire: qcom : use FIELD_{GET|PREP}") seems to have
> accidentally removed clearing bit field while modifying the register.
> 
> Fix this by adding back clear register mask before setting it up!
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  drivers/soundwire/qcom.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> index d7aabdaffee3..5d26361ab4f6 100644
> --- a/drivers/soundwire/qcom.c
> +++ b/drivers/soundwire/qcom.c
> @@ -311,6 +311,7 @@ static int qcom_swrm_init(struct qcom_swrm_ctrl *ctrl)
>  
>  	/* Configure No pings */
>  	ctrl->reg_read(ctrl, SWRM_MCP_CFG_ADDR, &val);
> +	val &= ~SWRM_MCP_CFG_MAX_NUM_OF_CMD_NO_PINGS_BMSK;
>  	val |= FIELD_PREP(SWRM_MCP_CFG_MAX_NUM_OF_CMD_NO_PINGS_BMSK, SWRM_DEF_CMD_NO_PINGS);

Should we rather use u32_replace_bits() here, I think the intention is
to replace bits.

>  	ctrl->reg_write(ctrl, SWRM_MCP_CFG_ADDR, val);
>  
> @@ -372,6 +373,9 @@ static int qcom_swrm_pre_bank_switch(struct sdw_bus *bus)
>  
>  	ctrl->reg_read(ctrl, reg, &val);
>  
> +	val &= ~SWRM_MCP_FRAME_CTRL_BANK_COL_CTRL_BMSK;
> +	val &= ~SWRM_MCP_FRAME_CTRL_BANK_ROW_CTRL_BMSK;
> +
>  	val |= FIELD_PREP(SWRM_MCP_FRAME_CTRL_BANK_COL_CTRL_BMSK, SWRM_MAX_COL_VAL);
>  	val |= FIELD_PREP(SWRM_MCP_FRAME_CTRL_BANK_ROW_CTRL_BMSK, SWRM_MAX_ROW_VAL);
>  
> -- 
> 2.21.0

-- 
~Vinod