From: Heiko Stuebner <heiko@sntech.de>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: thierry.reding@gmail.com, mark.rutland@arm.com,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, robh+dt@kernel.org,
christoph.muellner@theobroma-systems.com
Subject: Re: [PATCH 3/3] drm/panel: add panel driver for Xinpeng XPP055C272 panels
Date: Sun, 15 Dec 2019 10:13:29 +0100 [thread overview]
Message-ID: <1744285.zQlJhejOUX@phil> (raw)
In-Reply-To: <20191215082916.GA25772@ravnborg.org>
Hi Sam,
Am Sonntag, 15. Dezember 2019, 09:29:16 CET schrieb Sam Ravnborg:
> Hi Heiko.
>
> > Am Samstag, 14. Dezember 2019, 09:17:30 CET schrieb Sam Ravnborg:
> > > > +#define dsi_generic_write_seq(dsi, cmd, seq...) do { \
> > > > + static const u8 d[] = { seq }; \
> > > > + int ret; \
> > > > + ret = mipi_dsi_dcs_write(dsi, cmd, d, ARRAY_SIZE(d)); \
> > > > + if (ret < 0) \
> > > > + return ret; \
> > > > + } while (0)
> > > This macro return an error code if a write fails.
> > >
> > > > +
> > > > +static int xpp055c272_init_sequence(struct xpp055c272 *ctx)
> > > > +{
> > > > + struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> > > > + struct device *dev = ctx->dev;
> > > > + int ret;
> > > > +
> > > > + /*
> > > > + * Init sequence was supplied by the panel vendor without much
> > > > + * documentation.
> > > > + */
> > > > + dsi_generic_write_seq(dsi, XPP055C272_CMD_SETEXTC, 0xf1, 0x12, 0x83);
> > > But all uses of the macro here ignore the error.
> >
> > hmm, am I way off track here?
> >
> > dsi_generic_write_seq(dsi, XPP055C272_CMD_SETEXTC, 0xf1, 0x12, 0x83);
> > dsi_generic_write_seq(dsi, XPP055C272_CMD_SETMIPI,
> > 0x33, 0x81, 0x05, 0xf9, 0x0e, 0x0e, 0x00, 0x00,
> > 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25,
> > 0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4f, 0x01,
> > 0x00, 0x00, 0x37);
> > ...
> >
> > should just expand to
> >
> > do {
> > static const u8 d[] = { 0xf1, 0x12, 0x83 };
> > int ret;
> > ret = mipi_dsi_dcs_write(dsi, XPP055C272_CMD_SETEXTC, d, ARRAY_SIZE(d));
> > if (ret < 0)
> > return ret;
> > } while (0)
> > do {
> > static const u8 d[] = { 0x33, 0x81, 0x05, 0xf9, 0x0e, 0x0e, 0x00, 0x00,
> > 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25,
> > 0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4f, 0x01,
> > 0x00, 0x00, 0x37 };
> > int ret;
> > ret = mipi_dsi_dcs_write(dsi, XPP055C272_CMD_SETMIPI, d, ARRAY_SIZE(d));
> > if (ret < 0)
> > return ret;
> > } while (0)
> > ...
> >
> > so every write instance will actually return an error if it happens and not
> > continue on with the next init item.
> The idea was that if a write returned an error then do not even attempt
> more writes. So if a write fails we do not loose the original error
> code, assuming subsequent write would also fail.
Shouldn't the code above do exactly that? ... Because it's like
ret = dcs_write(...)
if (ret <0)
return ret;
So if any of the dcs_writes goes wrong it should just return the
error code from that write from the function and not try any more
writes. (or I'm blind and do not see something ;-) )
Heiko
> I have looked through all the panel drivers now, and the majority does
> not check if the write goes wrong.
> So following the pattern on the other panels you can also decide to just
> ignore the return value of mipi_dsi_dcs_write() rahter than trying to
> invent the check I tried to explain.
>
> Sam
>
next prev parent reply other threads:[~2019-12-15 9:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-09 14:42 [PATCH 1/3] dt-bindings: Add vendor prefix for Xinpeng Technology Heiko Stuebner
2019-12-09 14:42 ` [PATCH 2/3] dt-bindings: display: panel: Add binding document for Xinpeng XPP055C272 Heiko Stuebner
2019-12-14 7:54 ` Sam Ravnborg
2019-12-09 14:42 ` [PATCH 3/3] drm/panel: add panel driver for Xinpeng XPP055C272 panels Heiko Stuebner
2019-12-14 8:17 ` Sam Ravnborg
2019-12-14 23:07 ` Heiko Stübner
2019-12-15 8:29 ` Sam Ravnborg
2019-12-15 9:13 ` Heiko Stuebner [this message]
2019-12-15 9:40 ` Sam Ravnborg
2019-12-14 7:50 ` [PATCH 1/3] dt-bindings: Add vendor prefix for Xinpeng Technology Sam Ravnborg
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