linux-kernel - Re: [alsa-devel] [Patch v6 2/7] slimbus: Add messaging APIs to slimbus framework

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Message-ID: <20171011102436.GH30097@localhost>
Date:   Wed, 11 Oct 2017 15:54:36 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     gregkh@...uxfoundation.org, broonie@...nel.org,
        alsa-devel@...a-project.org, mark.rutland@....com,
        michael.opdenacker@...e-electrons.com, poeschel@...onage.de,
        andreas.noever@...il.com, gong.chen@...ux.intel.com, arnd@...db.de,
        kheitke@...ience.com, bp@...e.de, devicetree@...r.kernel.org,
        james.hogan@...tec.com, pawel.moll@....com,
        linux-arm-msm@...r.kernel.org, sharon.dvir1@...l.huji.ac.il,
        robh+dt@...nel.org, sdharia@...eaurora.org, alan@...ux.intel.com,
        treding@...dia.com, mathieu.poirier@...aro.org, jkosina@...e.cz,
        linux-kernel@...r.kernel.org, daniel@...ll.ch, joe@...ches.com,
        davem@...emloft.net
Subject: Re: [alsa-devel] [Patch v6 2/7] slimbus: Add messaging APIs to
 slimbus framework

On Wed, Oct 11, 2017 at 10:42:28AM +0100, Srinivas Kandagatla wrote:
> On 11/10/17 05:38, Vinod Koul wrote:
> >On Fri, Oct 06, 2017 at 05:51:31PM +0200, srinivas.kandagatla@...aro.org wrote:
> >
> >>  	mutex_init(&ctrl->m_ctrl);
> >>+	spin_lock_init(&ctrl->tx.lock);
> >>+	spin_lock_init(&ctrl->rx.lock);
> >
> >locks galore :) My assumption is that you want to optimize these? But given
> >that audio user is going to be serialized do we practically need two locks?
> >
> If we remove the locking, It will be issue if we have multiple devices in a
> component, which is common atleast with the codec which am looking at.

can you explian what you mean by a "device" here?

> >>+	switch (mc) {
> >>+	case SLIM_MSG_MC_REQUEST_VALUE:
> >>+	case SLIM_MSG_MC_REQUEST_INFORMATION:
> >
> >what does MC refer to?
> 
> Message Code.

isnt SLIM_MSG enough :D I think we cna get rid of MC here..

> >>+struct slim_val_inf {
> >>+	u16			start_offset;
> >>+	u8			num_bytes;
> >>+	u8			*rbuf;
> >>+	const u8		*wbuf;
> >
> >can we do read and write, if not it can be a buf which maybe rbuf or wbug
> >based on type
> With REQUEST_CHANGE_VALUE single command we can read old value at the same
> time we can write new value.

so that is a read modify write, correct? Is that implemented in HW, if so we
need to provide only write value

-- 
~Vinod