[PATCH] clk: ast2600: enable BCLK for PCI/PCIe bus always

Jae Hyun Yoo jae.hyun.yoo at linux.intel.com
Thu Jan 16 07:21:33 AEDT 2020

On 1/14/2020 9:43 PM, Joel Stanley wrote:
> On Tue, 14 Jan 2020 at 19:53, Jae Hyun Yoo <jae.hyun.yoo at 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 at 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.

Looks like it needs changes in clk-ast2600 module for checking of
'clock-critical' device tree property. Let me try to make it.


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