linux-kernel - Re: [PATCH 06/14] soundwire: Add IO transfer

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Date:   Sat, 21 Oct 2017 10:29:08 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        ALSA <alsa-devel@...a-project.org>, Takashi <tiwai@...e.de>,
        Pierre <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Shreyas NC <shreyas.nc@...el.com>, patches.audio@...el.com,
        alan@...ux.intel.com,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Sagar Dharia <sdharia@...eaurora.org>,
        srinivas.kandagatla@...aro.org, plai@...eaurora.org,
        Sudheer Papothi <spapothi@...eaurora.org>
Subject: Re: [PATCH 06/14] soundwire: Add IO transfer

On Thu, Oct 19, 2017 at 08:33:22AM +0530, Vinod Koul wrote:

> +static bool sdw_get_page(struct sdw_slave *slave, struct sdw_msg *msg)
> +{
> +	bool page = false, paging_support = false;
> +
> +	if (slave && slave->prop.paging_support)
> +		paging_support = true;
> +
> +	/*
> +	 * Programme SCP page addr for:
> +	 * 1. addr_page1 and addr_page2 contains non-zero values.
> +	 * 2. Paging supported by Slave.
> +	 */
> +	switch (msg->dev_num) {
> +	case SDW_ENUM_DEV_NUM:
> +	case SDW_BROADCAST_DEV_NUM:
> +		break;
> +
> +	default:
> +		if (paging_support && ((msg->addr_page1) || (msg->addr_page2)))
> +			page = true;
> +	}
> +
> +	return page;

So if a page was specified but we don't have paging support we silently
just write to the base pagee?

> +int sdw_transfer(struct sdw_bus *bus, struct sdw_slave *slave,
> +					struct sdw_msg *msg)
> +{
> +	bool page;
> +	int ret;
> +
> +	mutex_lock(&bus->msg_lock);
> +
> +	page = sdw_get_page(slave, msg);

get_page() doesn't interact with the hardware at all so it could be
outside the lock.

> +	ret = do_transfer(bus, msg, page);
> +	if (ret != 0 && ret != -ENODATA) {
> +		dev_err(bus->dev, "trf on Slave %d failed:%d\n",
> +				msg->dev_num, ret);
> +		goto error;
> +	}
> +
> +	if (page)
> +		ret = sdw_reset_page(bus, msg->dev_num);

Wouldn't it be safer to reset the page even on error so future messages
go to the right place if the paging bit of the failed operation worked?

> +int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
> +{
> +	struct sdw_msg msg;
> +	int ret;
> +
> +	pm_runtime_get_sync(slave->bus->dev);

No error check.

> +	pm_runtime_get_sync(slave->bus->dev);
> +
> +	sdw_fill_msg(&msg, addr, count, slave->dev_num, SDW_MSG_FLAG_WRITE, val);

The device doesn't need to be powered up for us to fill in the data
structures we're going to use.

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