ONFI timing mode with onfi_set_features unsupported

[Sascha Hauer]

On Mon, Nov 21, 2016 at 02:51:04PM +0100, Boris Brezillon wrote:
> Hi Sascha,
> 
> On Mon, 21 Nov 2016 14:23:27 +0100
> Sascha Hauer <s.hauer at pengutronix.de> wrote:
> 
> > Hi all,
> > 
> > I have a i.MX6ul here with a Cypress S34ML04G2 connected. This Nand chip
> > has ONFI support, but onfi_set_features is unsupported (opt_cmd is
> > 0x3b). Currently the gpmi Nand driver calls nand_onfi_set_features(),
> > gets -EINVAL as error and continues with a very slow default timing.
> > 
> > I assume the nand_onfi_set_features() call is just unnecessary for this
> > chip, if I skip it, the chip works with the fast timing.
> > 
> > Any idea how to cope with this situation? I attached the most obvious
> > patch, but it looks a bit hackish. Any suggestions or is the patch fine
> > as is?
> 
> It looks good to me. Why do you find this code hackish?
> Of course, it would be even better to implement the
> ->setup_data_interface() method.

Indeed, but my current project doesn't allow to spend that much time at
the moment.

> 
> BTW, can you patch the core to only send the ->set_feature() command
> (to change the timings mode) when the chip supports it?

With hackish I mean that I think the problem should be solved in the
core. How about returning -EOPNOTSUPP from onfi_set_features() when the
operation is not supported? The caller could then decide what to do
without testing for bits in the onfi param page.

Sascha

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