Re: [PATCH v3 3/3] counter: 104-quad-8: Utilize helper functions to handle PR, FLAG and PSC

Andy Shevchenko
2023-04-11T14:44:03Z

On Tue, Apr 11, 2023 at 10:05:25AM -0400, William Breathitt Gray wrote:
> On Tue, Apr 11, 2023 at 04:50:03PM +0300, Andy Shevchenko wrote:
> > On Mon, Apr 10, 2023 at 10:03:13AM -0400, William Breathitt Gray wrote:
> > > The Preset Register (PR), Flag Register (FLAG), and Filter Clock
> > > Prescaler (PSC) have common usage patterns. Wrap up such usage into
> > > dedicated functions to improve code clarity.

...

> > > *val = 0;
> >
> > Is not needed now as always being initialized by below call.
>
> The regmap_noinc_read() call only reads the number of bytes requested.
> Since we request 3 bytes, the upper bytes of the u64 val remain
> uninitialized, so that is why we need to set *val = 0. This isn't
> immediately clear in the code, so I can add a comment to make it
> explicit.

Hmm...
Since we are using byte array for the value, can we actually use
memset() to show that explicitly? Perhaps in that way it will be more visible?

> > > spin_lock_irqsave(&priv->lock, irqflags);
> > >
> > > iowrite8(SELECT_RLD | RESET_BP | TRANSFER_CNTR_TO_OL, &chan->control);
> > > -
> > > - for (i = 0; i < 3; i++)
> > > - *val |= (unsigned long)ioread8(&chan->data) << (8 * i);
> > > + ioread8_rep(&chan->data, val, 3);

But hold on, wouldn't this have an endianess issue? The call fills in LE,
while here you use the CPU order.

> > > spin_unlock_irqrestore(&priv->lock, irqflags);

That said, I think you should have something like

u8 value[3];

ioread8_rep(..., value, sizeof(value));

*val = get_unaligned_le24(value);

--
With Best Regards,
Andy Shevchenko