[U-Boot] [PATCH v2 10/19] spi: mpc8xxx: Simplify logic a bit

[Joakim Tjernlund]

On Thu, 2019-05-02 at 07:31 +0200, Mario Six wrote:
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> 
> Hi Jagan and Jocke,
> 
> I'm back from vacation, so here's my answer:
> 
> On Mon, Apr 29, 2019 at 12:41 PM Jagan Teki <jagan at amarulasolutions.com> wrote:
> > + Mario
> > 
> > On Mon, Apr 29, 2019 at 2:48 PM Joakim Tjernlund
> > <Joakim.Tjernlund at infinera.com> wrote:
> > > On Mon, 2019-04-29 at 01:58 +0530, Jagan Teki wrote:
> > > > From: Mario Six <mario.six at gdsys.cc>
> > > > 
> > > > We do nothing in the loop if the "not empty" event was not detected. To
> > > > simplify the logic, check if this is the case, and skip the execution of
> > > > the loop early to reduce the nesting level and flag checking.
> > > 
> > > Looked at the driver to refresh memory and noticed:
> > > if (charSize == 32) {
> > >         /* Advance output buffer by 32 bits */
> > >         din += 4;
> > > }
> > > which suggests that only 32 bit char will increase the din ptr so does other bitlens
> > > work for reading?
> Yes, It will work. When charSize < 32 in a loop execution, we necessarily also
> have numBlks == 0, since numBlks = DIV_ROUND_UP(bitlen, 32) and charSize =
> (bitlen >= 32 ? 32 : bitlen); in other words: we're at the very end of the data
> to be sent/received and also the final loop execution, so we don't have to
> advance the pointer anymore.

Ahh, I see now.

But this over use of always 32 bits cause complexity/subtile bugs. The driver should use
the requested charsize(wordlen) throughout. As is now you cannot use the NF/NE flag as intended or
toggle LSB_FIRST
I think fsl_espi driver is worse though.

    Jocke