Re: [RFC PATCH] drivers: bus: add ARM CCI support

[Stephen Boyd <sboyd@codeaurora.org>]

On 04/18/13 10:54, Nicolas Pitre wrote:
> On Thu, 18 Apr 2013, Stephen Boyd wrote:
>
>> On 04/11/13 07:47, Lorenzo Pieralisi wrote:
>>> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
>>> new file mode 100644
>>> index 0000000..81953de
>>> --- /dev/null
>>> +++ b/drivers/bus/arm-cci.c
>> [...]
>>> +static void notrace cci_port_control(unsigned int port, bool enable)
>>> +{
>>> +	void __iomem *base = ports[port].base;
>>> +
>>> +	if (!base)
>>> +		return;
>>> +
>>> +	writel_relaxed(enable, base + CCI_PORT_CTRL);
>>> +	while (readl_relaxed(cci_ctrl_base + CCI_CTRL_STATUS) & 0x1)
>>> +			;
>> cpu_relax()?
> In some cases there is no more cache coherence when this is called and 
> the hardware might not be in a good state to cope with whatever action 
> people might be tempted to insert into cpu_relax().  After the CCI is 
> disabled it is important to keep a low profile and not touch anything 
> global. With some early hardware revision, even a DMB here was harmful.

Fair enough. Perhaps the code could use a comment to that effect.

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