On Mon, 21 Oct 2024, Andy Shevchenko wrote:
> On Mon, Oct 21, 2024 at 12:24:57PM +0300, Ilpo Järvinen wrote:
> > On Mon, 21 Oct 2024, Andy Shevchenko wrote:
> >
> > > The theory is that the so called workaround in pwr_reg_rdwr() is
> > > the actual reader of the data in 32-bit chunks. For some reason
> > > the 8-bit IO won't fail after that. Replace the workaround by using
> > > 32-bit IO explicitly and then memcpy() as much data as was requested
> > > by the user. The same approach is already in use in
> > > intel_scu_ipc_dev_command_with_size().
>
> ...
>
> > > err = intel_scu_ipc_check_status(scu);
> > > - if (!err && id == IPC_CMD_PCNTRL_R) { /* Read rbuf */
> > > - /* Workaround: values are read as 0 without memcpy_fromio */
> > > - memcpy_fromio(cbuf, scu->ipc_base + 0x90, 16);
> > > - for (nc = 0; nc < count; nc++)
> > > - data[nc] = ipc_data_readb(scu, nc);
> > > + if (!err) { /* Read rbuf */
> >
> > What is the reason for the removal of that id check? This seems a clear
> > logic change but why? And if you remove want to remove that check, what
> > that comment then means?
>
> Let me split this to a separate change with better explanation then.
>
> > > + for (nc = 0, offset = 0; nc < 4; nc++, offset += 4)
> > > + wbuf[nc] = ipc_data_readl(scu, offset);
> > > + memcpy(data, wbuf, count);
> >
> > So do we actually need to read more than
> > DIV_ROUND_UP(min(count, 16U), sizeof(u32))? Because that's the approach
> > used in intel_scu_ipc_dev_command_with_size() which you referred to.
>
> I'm not sure I follow. We do IO for whole (16-bytes) buffer, but return only
> asked _bytes_ to the user.
So always reading 16 bytes is not part of the old workaround? Because it
has a "lets read enough" feel.
> > > }
> > > mutex_unlock(&ipclock);
> > > return err;
> >
> > FYI (unrelated to this patch), there seems to be some open-coded
> > FIELD_PREP()s in pwr_reg_rdwr(), some of which is common code between
> > those if branches too.
>
> This code is quite old and full of tricks that has to be tested. So, yes
> while it's possible to convert, I would like to do it in a small (baby)
> steps. This series is already quite intrusive from this perspective :-)
Yeah, no pressure, I just noted down what I saw. :-)
--
i.
