On Mon, Oct 14, 2013 at 08:58:34AM +0300, Terje Bergström wrote: > On 12.10.2013 01:43, Stephen Warren wrote: > > On 10/07/2013 02:34 AM, Thierry Reding wrote: > >> The gr2d hardware in Tegra114 is compatible with that of Tegra20 and > >> Tegra30. No functionaly changes are required. > > Similarly here, if the HW is 100% backwards-compatible, there's no need > > to add compatible values to the driver. > > We've used this mechanism for attaching a per-hw-version data structure > in match table to accomodate differences in how the hardware is power > gated, reset, booted, some per-soc performance related changes etc. It's > also used in staging features for new chips, such as disabling power > features when they're not working/verified yet. > > Upstream driver is not yet in a state where that is relevant. > > With this, would we still be able to do that with match table? It sounds > like we could, because we can still (even with multiple compatible > properties) add separate entries in match table and I guess the > compatible properties matched in order.
Yes, as long as the device tree files includes the most specific value
in the compatible this should still be possible. So we'd have this:
gr2d@54140000 {
compatible = "nvida,tegra114-gr2d", "nvidia,tegra20-gr2d";
...
};
and the driver will match on "nvidia,tegra20-gr2d" if the more specific
"nvidia,tegra114-gr2d" is not there. When the driver is updated to
support Tegra114 specific functionality, then a more specific entry can
be added to the compatible table to handle it.
Thierry
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