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SubjectRe: [PATCH v5 4/5] drm: imx: Add i.MX 6 MIPI DSI host platform driver
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On Tue, 2020-03-31 at 00:31 +0300, Adrian Ratiu wrote:
> On Mon, 30 Mar 2020, Ezequiel Garcia <ezequiel@collabora.com>
> wrote:
> > Hello Fabio, Adrian:
> >
> > On Mon, 2020-03-30 at 08:49 -0300, Fabio Estevam wrote:
> > > Hi Adrian, On Mon, Mar 30, 2020 at 8:34 AM Adrian Ratiu
> > > <adrian.ratiu@collabora.com> wrote:
> > > > This adds support for the Synopsis DesignWare MIPI DSI v1.01
> > > > host controller which is embedded in i.MX 6 SoCs. Based on
> > > > following patches, but updated/extended to work with existing
> > > > support found in the kernel: - drm: imx: Support Synopsys
> > > > DesignWare MIPI DSI host controller
> > > > Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
> > > > - ARM: dtsi: imx6qdl: Add support for MIPI DSI host
> > > > controller
> > > > Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
> > > This one looks like a devicetree patch, but this patch does
> > > not touch devicetree.
> > > > + ret = clk_prepare_enable(dsi->pllref_clk); + if
> > > > (ret) { + dev_err(dev, "%s: Failed to enable
> > > > pllref_clk\n", __func__); + return ret; +
> > > > } + + dsi->mux_sel =
> > > > syscon_regmap_lookup_by_phandle(dev->of_node, "fsl,gpr"); +
> > > > if (IS_ERR(dsi->mux_sel)) { + ret =
> > > > PTR_ERR(dsi->mux_sel); + dev_err(dev, "%s:
> > > > Failed to get GPR regmap: %d\n", +
> > > > __func__, ret); + return ret;
> > > You should disable the dsi->pllref_clk clock prior to
> > > returning the error.
> >
> > Another approach could be moving the clock on and off to to
> > component_ops.{bind,unbind} (as rockhip driver does).
> >
> > What exactly is the PLL clock needed for? Would it make sense to
> > move it some of the PHY power on/off? (Maybe not, but it's
> > worthing checking).
> >
> > Also, it seems the other IP blocks have this PLL clock, so maybe
> > it could be moved to the dw_mipi_dsi core? This could be
> > something for a follow-up, to avoid creeping this series.
>
> Hi Ezequiel,
>
> pll is the video reference clock which drives the data lanes and
> yes all drivers have it as it's a basic requirement, so moving it
> to the common bridge is indeed a good idea, however this kind of
> driver refactoring is out of scope for this specific patch series,
> because, for now, I'd like to get the regmap and the imx6 driver
> in, once that is done we can think how to further abstract away
> common logic and slim down the existing drivers further.
>
> Basically I just want to avoid feature creep as I expect v6 to be
> ~ 8 patches big and the series is already over 1200 lines.
>

Oh, absolutely: if there's one thing I try to avoid is
feature creep -- together with bikeshedding!

Do note however, that you could move the PLL clock handling
to component_ops.{bind,unbind} and maybe simplify the error
handling.

(BTW, great work!)

Cheers,
Ezequiel



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