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From: Joel Stanley <joel@jms.id.au>
To: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Cc: Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Andrew Jeffery <andrew@aj.id.au>,
	linux-clk@vger.kernel.org,
	linux-aspeed <linux-aspeed@lists.ozlabs.org>
Subject: Re: [PATCH] clk: ast2600: enable BCLK for PCI/PCIe bus always
Date: Wed, 15 Jan 2020 05:43:03 +0000
Message-ID: <CACPK8XfevBQxdAanN5QjiUv8KKevetjKP7cbr3tuL=mrULjttg@mail.gmail.com> (raw)
In-Reply-To: <255b53d2-d4b5-8bc0-393b-a2f531a98fc1@linux.intel.com>

On Tue, 14 Jan 2020 at 19:53, Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> wrote:
>
> Hi Joel,
>
> On 1/13/2020 10:15 PM, Joel Stanley wrote:
> > On Mon, 13 Jan 2020 at 21:33, Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> wrote:
> >>
> >> BCLK for PCI/PCIe bus should be enabled always with having the
> >> CLK_IS_CRITICAL flag otherwise it will be disabled at kernel late
> >> initcall phase as an unused clock, and eventually it causes
> >> unexpected behavior on BMC features that are connected to the host
> >> through PCI/PCIe bus.
> >
> > This is true for systems that have PCIe connected. There are systems
> > that do not, and in that case we don't want to have the clock enabled.
> >
> > Are you doing this to support the case where the PCIe device not load
> > a BMC driver? (eg for host VGA use). If not, then you can have the
> > driver you're loading request the BCLK.
> >
> > If this is for the host VGA device, then you will need to come up with
> > a mechanism that makes the enabling of this clock depend on the device
> > tree.
>
> Is there any way to enable clock by just adding a node in device tree?
> Do you want me to add a simple driver module for host VGA just for
> enabling BCLK?

Okay, so this is for the case where we lack a BMC driver.

One option would be to do as you suggest, adding a simple driver that
claims essential clocks.

Another could be to add some extra properties that clock driver parses
and enables the clocks.

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 21:34 Jae Hyun Yoo
2020-01-14  6:15 ` Joel Stanley
2020-01-14 19:53   ` Jae Hyun Yoo
2020-01-15  5:43     ` Joel Stanley [this message]
2020-01-15 20:21       ` Jae Hyun Yoo

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