[PATCH v2 26/27] drm/tegra: Add DSI support

[Thierry Reding]

On Tue, Oct 15, 2013 at 11:21:07AM -0600, Stephen Warren wrote:
> On 10/15/2013 02:33 AM, Thierry Reding wrote:
> > On Mon, Oct 14, 2013 at 12:16:48PM -0600, Stephen Warren wrote:
> >> On 10/14/2013 07:55 AM, Thierry Reding wrote:
> >>> On Fri, Oct 11, 2013 at 04:43:35PM -0600, Stephen Warren
> >>> wrote:
> >>>> On 10/07/2013 02:34 AM, Thierry Reding wrote:
> >>>>> This commit adds support for both DSI outputs found on
> >>>>> Tegra. Only very minimal functionality is implemented, so
> >>>>> advanced features like ganged mode won't work.
> >>>>> 
> >>>>> Due to the lack of other test hardware, some sections of
> >>>>> the driver are hardcoded to work with Dalmore.
> >>>> 
> >>>>> diff --git a/drivers/gpu/drm/tegra/dsi.c
> >>>>> b/drivers/gpu/drm/tegra/dsi.c
> >>>> 
> >>>>> +static int tegra_dsi_show_regs(struct seq_file *s, void
> >>>>> *data) +{ +	struct drm_info_node *node = s->private; +
> >>>>> struct tegra_dsi *dsi = node->info_ent->data; + +#define
> >>>>> DUMP_REG(name)						\ +	seq_printf(s, "%-32s %#05x
> >>>>> %08lx\n", #name, name,	\ +		   tegra_dsi_readl(dsi, name)) 
> >>>>> + +	DUMP_REG(DSI_INCR_SYNCPT);
> >>>> 
> >>>> Does it make sense to use an MMIO regmap instead? That way,
> >>>> you get all the debugfs files for free...
> >>> 
> >>> As far as I know, regmap doesn't give you the symbolic names
> >>> for the registers. I find that a rather useful feature because
> >>> it allows to easily compare the registers to the ones in our
> >>> downstream kernels.
> >> 
> >> True. However, we should really be writing user-space scripts to
> >> encode that information. Such a script could be useful e.g. if
> >> reading the information directly from /dev/mem or JTAG too, and
> >> bloating the kernel with debug strings doesn't seem like a great
> >> idea.
> > 
> > I don't agree. While I see some value in having such userspace
> > scripts, having the symbolic names in debugfs allows anyone to look
> > at a readable form of the data without having to have access to
> > those scripts. Besides it's called *debug*fs for a purpose, isn't
> > it? There's plenty of edited data that's not just a plain dump of
> > data.
> 
> Perhaps you should work to enhance regmap's debugfs files to support
> optionally naming registers?

Just to follow up with what we've discussed on IRC: I'll take a stab at
refactoring the debugfs file output into something more generic that can
possibly be leveraged by regmap as well. That should provide a somewhat
more lightweight alternative to regmap for implementations that don't
need regmap for anything else while at the same time providing something
so not every driver has to come up with something custom.

Does that sum it up correctly?

Thierry
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