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SubjectRE: [PATCH V18 4/6] i2c: tegra: Add DMA support
Date
> > > I am not sure if you are aware of this document, so I mention it:
> > >
> > > Documentation/i2c/DMA-considerations
> > >
> > > I am not pushing you to use the i2c_get_dma_safe_msg_buf() helpers,
> > > just wanted to make sure you know about them. I am also fine with an
> > > incremental patch on top of this if you want to add usage of those
> > > helpers somewhen later.
> >
> > At least I was not aware of those helpers. It looks to me that the
> > approach of having a statically allocated buffer is more optimal than
> > having to allocate and map the buffer on each transfer.
>
> Can be argued, yes.
>
> > >> /* Match table for of_platform binding */ static const struct
> > >> of_device_id tegra_i2c_of_match[] = {
> > >> { .compatible = "nvidia,tegra194-i2c", .data = &tegra194_i2c_hw,
> > >> },
> > >> + { .compatible = "nvidia,tegra186-i2c", .data = &tegra186_i2c_hw,
> > >> +},
> > >> { .compatible = "nvidia,tegra210-i2c", .data = &tegra210_i2c_hw, },
> > >> { .compatible = "nvidia,tegra124-i2c", .data = &tegra124_i2c_hw, },
> > >> { .compatible = "nvidia,tegra114-i2c", .data = &tegra114_i2c_hw,
> > >> },
> > >
> > > Shouldn't this be a seperate patch?
> >
> > I asked for this change and no, it shouldn't be a separate patch as it
> > adds "has_apb_dma = false" property for T186 that older Tegra's have
> > as "true". Without this change T186 uses tegra_i2c_hw_feature of T210,
> > see [0]. Hence this change is absolutely correct and appropriate for
> > this patch.
>
> Then please update the patch description to contain this information.
>
Will update commit message about the reason for adding has_apb_dma
>
>
> > > This should definately be a seperate patch. While I am all for
> > > taking it, are you sure it does not regress on older Tegra platforms?
> > >
> >
> > All the patches are tested on older Tegra's (T20/T30 specifically by
> > me) and we fixed several bugs that were regressing them over the few
> > versions of the patchset. I specifically asked for this change for
> > older Tegra's because the APBDMA driver (T20-T210) is getting
> > registered from the module-init level and hence I2C driver probe is
> > always getting deferred. I'm not sure that it's worth to factor out
> > this hunk into a separate patch as it's directly related to the DMA
> > support addition, maybe worth to mention why this is needed in the
> > commit message.
>
> At least, this, yes.
>
Will update commit message to reflect this...
>
>

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