Best practice to lock a read/write to a HW register

[manty kuma]

Ideally, it depends on the platform you are working. You need to discuss
with them for the correct approach. For Qualcomm they have some hardware
caled as RPU(Register protection unit). They have systems calls exposed for
using them. You can associtate it to the register you want protection. I
dont know if there is any way you could do it in Linux itself?

Regards,
Sandeep


On Thu, Nov 14, 2013 at 9:14 PM, Bernd Petrovitsch <
bernd at petrovitsch.priv.at> wrote:

> Hi!
>
> On Don, 2013-11-14 at 11:32 +0100, Luca Ellero wrote:
> [...]
> > can someone please show me which is the best practice to lock a
> > read/write to a hardware register.
> > In other words if, in a driver, I want to modify a bit in a HW register,
> > I have to read the register, set/reset the relevant bit and write back
> > the reg.
> > But what can I do to be sure that no other code modifies the register
> > between my read and write?
> > Is spin_lock() suitable for this purpose?
>
> If the read-modify-write (read: the critical section) run-time is short,
> a spin-lock is the usual means. If it is needed from IRQ-context - see
> also other mails - you must use the *_irq() variant.
>
>         Bernd
> --
> Bernd Petrovitsch                  Email : bernd at petrovitsch.priv.at
>                      LUGA : http://www.luga.at
>
>
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