lkml.org 
[lkml]   [2011]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Locking in the clk API
    On Tue, Jan 11, 2011 at 05:44:59PM +0800, Jeremy Kerr wrote:
    > So, it sounds like the best approach is to provide an atomic clk_enable. I
    > agree with Sascha that the clk_enable and clk_enable_atomic polarity makes the
    > most sense, so how about:
    >
    > int clk_enable(struct clk *clk)
    > {
    > might_sleep();
    >
    > [...]
    > }
    >
    > int clk_enable_atomic(struct clk *clk)
    > {
    > BUG_ON(!(clk->flags & CLK_ATOMIC));
    >
    > [...]
    > }
    >
    > Paul: even though you mention that the atomic clocks are the usual case, I
    > think that this way around illustrates the atomic 'restriction' at the call
    > site more clearly. When the drivers don't care about the atomicity,
    > clk_enable() is fine. When drivers do need an atomic clock,
    > clk_enable_atomic() shows this requirement.
    >
    No, the sleeping clock case is and always will be a corner case, and I
    have no interest in pretending otherwise. On SH we have hundreds of
    clocks that are all usable in the atomic context and perhaps less than a
    dozen that aren't (and even in those cases much of the PLL negotiation is
    handled in hardware so there's never any visibility for the lock-down
    from the software side, other architectures also have similar behaviour).

    Keep in mind that all users except for the few that you cited were
    already quite content with the atomic context use, so this 'restriction'
    you speak of is just an artificial limitation introduced by a couple of
    new platforms that deviated from what everyone else was already doing.

    If you want to go this route, then SH and ARM-based SH-Mobiles will at
    least not be making use of the generic struct clk.


    \
     
     \ /
      Last update: 2011-01-11 11:17    [W:4.127 / U:0.512 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site