linux-kernel - Re: [PATCH v3 lora-next 5/5] net: lora: sx125x sx1301: allow radio to register as a clk provider

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Message-ID: <20190103123720.GR1846@sirena.org.uk>
Date:   Thu, 3 Jan 2019 12:37:20 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Andreas Färber <afaerber@...e.de>
Cc:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        Ben Whitten <ben.whitten@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        netdev@...r.kernel.org,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        "linux-lpwan@...ts.infradead.org" <linux-lpwan@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        starnight@...cu.edu.tw, "David S. Miller" <davem@...emloft.net>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 lora-next 5/5] net: lora: sx125x sx1301: allow radio
 to register as a clk provider

On Wed, Jan 02, 2019 at 01:44:40AM +0100, Andreas Färber wrote:

> So, the third invocation of sun6i_transfer_one() calling clk_get_rate()
> hangs at the prepare_lock instead of reference-counting, because it runs
> from a separate kthread, unlike the two previous calls?

If there's any contestation for the bus we push all the I/O through a
separate thread to maintain ordering and improve performance.

> I did not find any *regmap_init_spi() based example in drivers/clk/, and
> all other "spi" mentions in drivers/clk/ appeared to be clock names.
> The closest was devm_regmap_init_i2c() based clk-cdce706.c, which uses
> the prepare/unprepare ops, as suggested by Mark, and does
> regmap_update_bits() from there.

You'll find a bunch of the MFDs have SPI options as well.

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