Re: [PATCH] OMAP: DSS2: DSI: Support non-dcs long read

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

Hi,

On Fri, 2011-08-05 at 00:17 -0700, Arve Hjønnevåg wrote:
> 2011/8/5 Tomi Valkeinen <tomi.valkeinen@ti.com>:
> > On Thu, 2011-08-04 at 18:15 -0700, Arve Hjønnevåg wrote:
> >> 2011/8/4 Tomi Valkeinen <tomi.valkeinen@ti.com>:
> >> > Hi,
> >> >
> >> > On Wed, 2011-06-29 at 20:44 -0700, Arve Hjønnevåg wrote:
> >> >> Change-Id: I18168c887e1384c07dc033a1ffc57abdacb26073
> >> >> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> >> >> ---
> >> >>  drivers/video/omap2/dss/dsi.c |    7 ++++++-
> >> >>  1 files changed, 6 insertions(+), 1 deletions(-)
> >> >
> >> > This feels somehow partial... Why do you want to read generic packets if
> >> > there are no functions to send generic packets?
> >> >
> >>
> >> The chip responds with a generic packet when reading from some
> >> registers. This is a simple fix while adding support for sending
> >> generic packets would probably require an api change.
> >
> > What command do you use to read the register? DCS? If so, sounds rather
> > strange HW implementation.
> >
> 
> This change modifies dsi_vc_dcs_read to accept a generic response

Ok, so you do send a DCS read command, and you get a generic response.

> packet. If you want a separate generic read command that would also
> work, but the it would make it a little harder to write the driver
> since you then would need to know what type of response the chip
> sends.

Well, you do know what type of response the chip sends. According to
MIPI DSI spec, a DCS read is answered with DCS short/long response, and
a generic read is answered with generic short/long response.

If your HW doesn't work like that, it's against the spec. If a broken
chip like that was widely used, I guess we would have to add a hack for
that, but until such day I want to keep the driver working as the spec
says.

 Tomi


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