[RFC PATCH 04/12] arm: mm: cache-l2x0: add l2x0 suspend and resume functions

[Russell King - ARM Linux]

On Fri, Jan 29, 2010 at 10:29:32AM -0800, Daniel Walker wrote:
> On Fri, 2010-01-29 at 10:23 -0800, Ruan, Willie wrote:
> > > From: Daniel Walker [mailto:dwalker at codeaurora.org] 
> > > Sent: Friday, January 29, 2010 9:59 AM
> > >
> > > What if there are multiple cpu's calling cache_sync() at the same time?
> > > Disable interrupt wouldn't prevent it ..
> > 
> > cache_sync() is calling sync_writel(), which is using spin_lock_irqsave().
> > So, each call of cache_sync() and sync_writel() is SMP safe individually
> > in l2x0_flush_all() as in l2x0_inv_all(), unless we need to protect the
> > two calls together, which seems not necessary to me.
> 
> This is the current version,
> 
> static inline void cache_wait(void __iomem *reg, unsigned long mask)
> {
>         /* wait for the operation to complete */
>         while (readl(reg) & mask)
>                 ;
> }
> 
> static inline void cache_sync(void)
> {
>         void __iomem *base = l2x0_base;
>         writel(0, base + L2X0_CACHE_SYNC);
>         cache_wait(base + L2X0_CACHE_SYNC, 1);
> }
> 
> Maybe cache_sync was recently changed to "writel" instead sync_writel()
> due it getting called with the lock already held.

It's pointless discussing what the current code does, because that's
not what mainline does _today_ - the locking in this file has
completely changed.