linux-kernel - Re: [PATCH 1/2] mmc: sdhci: Add support for setting parent clock

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Date:   Mon, 20 Mar 2017 21:22:51 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Ritesh Harjani <riteshh@...eaurora.org>
Cc:     linux-mmc@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mmc: sdhci: Add support for setting parent clock

On 03/16/2017 12:32 PM, Jon Hunter wrote:
> It is common for SD/MMC host controllers to set the parent clock that
> drives the SD/MMC interface in order to support various operating
> speeds. Typically, this is performed by calling common clock framework
> APIs such as clk_set_rate(). The problem is that these APIs may sleep
> and must not be called from within atomic sections and therefore, these
> functions cannot be called within the existing 'set_clock' SDHCI
> operator because they are called from within the context of a spinlock.
> Add a new 'set_parent_clock' operator for the SDHCI driver that is
> called early during the SDHCI 'set_ios' before the spinlock is aquire to
> give the platform driver the opportunity to set the parent clock rate.

I just posted a patch to remove the spin lock from set_ios().  Does that help?