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

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Message-ID: <20200916144852.GS2968@vkoul-mobl>
Date:   Wed, 16 Sep 2020 20:18:52 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        yung-chuan.liao@...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.

On 16-09-20, 09:36, Pierre-Louis Bossart wrote:
> 
> 
> On 9/16/20 9:29 AM, Vinod Koul wrote:
> > On 16-09-20, 08:18, Pierre-Louis Bossart wrote:
> > > 
> > > > > According to usage (bitfields.h) of REG_FIELDS,
> > > > > Modify is:
> > > > >     reg &= ~REG_FIELD_C;
> > > > >     reg |= FIELD_PREP(REG_FIELD_C, c);
> > > 
> > > 
> > > if this is indeed the case, all the code in cadence_master.c is also broken,
> > > e.g:
> > > 
> > > 	dpn_config = cdns_readl(cdns, dpn_config_off);
> > > 
> > > 	dpn_config |= FIELD_PREP(CDNS_DPN_CONFIG_WL, (p_params->bps - 1));
> > > 	dpn_config |= FIELD_PREP(CDNS_DPN_CONFIG_PORT_FLOW, p_params->flow_mode);
> > > 	dpn_config |= FIELD_PREP(CDNS_DPN_CONFIG_PORT_DAT, p_params->data_mode);
> > 
> > This should be replaced with u32_replace_bits(), i am sending the fix
> 
> wondering if we should replace all uses of FIELD_PREP with either
> u32_insert_bits() or u32_encode_bits() then?

That might be overkill as in the rest of the cases we have

        foo = FIELD_PREP();
        foo |= FIELD_PREP();

so the first one would set the bitfield and clear the rest

Thanks
-- 
~Vinod