Re: [PATCH v2 2/2] irqchip: Add Qualcomm MPM controller driver

On Tue, Nov 30, 2021 at 01:19:48PM +0530, Maulik Shah wrote:

   Hi Shawn,

   On 11/30/2021 8:01 AM, Shawn Guo wrote:

+       do {
+               r_val = readl(priv->base + offset);
+               udelay(5);
+       } while (r_val != val);

What? Is this waiting for a bit to clear? Why isn't this one of the
read*_poll_timeout*() function instead? Surely you can't wait forever
here.

This is taken from downstream, and it seems to double check the written
value by reading it back.  But to be honest, I'm not really this is
necessary.  I will do some testing with the read-back check dropped.

How about asking for specs instead? There are QC people on Cc, and
many more reading the list. Hopefully they can explain what this is
all about.

Maulik,

If you have some information about this, that would be great.

   This can be converted to read poll_timeout(). This was introduced in
   place of wmb() to make sure writes are completed.

Hmm, in this case, writel() will just do the right thing, as it wraps
wmb() there.  Or am I missing something?

Shawn