Re: [PATCH V7 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

Peter Senna Tschudin
2017-02-01T10:58:43Z

Hi Archit,

On 01 February, 2017 10:44 CET, Archit Taneja <architt@codeaurora.org> wrote:

>
>
> On 01/30/2017 10:35 PM, Jani Nikula wrote:
> > On Sat, 28 Jan 2017, Peter Senna Tschudin <peter.senna@collabora.com> wrote:
> >> On Thu, Jan 05, 2017 at 01:18:47PM +0530, Archit Taneja wrote:
> >> Hi Archit,
> >>
> >> Thank you for the comments!
> >>
> >> [...]
> >>>> + total_size = (block[EDID_EXT_BLOCK_CNT] + 1) * EDID_LENGTH;
> >>>> + if (total_size > EDID_LENGTH) {
> >>>> + kfree(block);
> >>>> + block = kmalloc(total_size, GFP_KERNEL);
> >>>> + if (!block)
> >>>> + return NULL;
> >>>> +
> >>>> + /* Yes, read the entire buffer, and do not skip the first
> >>>> + * EDID_LENGTH bytes.
> >>>> + */
> >>>
> >>> Is this the reason why you aren't using drm_do_get_edid()?

> >>
> >> Yes, for some hw specific reason, it is necessary to read the entire
> >> EDID buffer starting from 0, not block by block.
> >
> > Hrmh, I'm planning on moving the edid override and firmware edid
> > mechanisms at the drm_do_get_edid() level to be able to truly and
> > transparently use a different edid. Currently, they're only used for
> > modes, really, and lead to some info retrieved from overrides, some from
> > the real edid. This kind of hacks will bypass the override/firmware edid
> > mechanisms then too. :(
>
> It seems like there is a HW issue which prevents them from reading EDID
> from an offset. So, I'm not sure if it is a hack or a HW limitation.

>
> One way around this would be to hide the HW requirement in the
> get_edid_block func pointer passed to drm_do_get_edid(). This
> would, however, result in more i2c reads (equal to # of extension
> blocks) than what the patch currently does.
>
> Peter, if you think doing extra EDID reads isn't too costly on your
> platform, you could consider using drm_do_get_edid(). If not, I guess
> you'll miss out on the additional functionality Jani is going to add

> in the future.

My concern is that for almost one year now, every time I fix something one or two new requests are made. I'm happy to fix the driver, but I want a list of the changes that are required to get it upstream, before I make more changes. Can we agree on exactly what is preventing this driver to get upstream? Then I'll fix it.

>
> Thanks,
> Archit
>
>
> >
> > BR,
> > Jani.
> >
> >
> >>
> >> [...]
> >>
> >> I fixed all your other suggestions. Thank you!
> >> _______________________________________________
> >> dri-devel mailing list
> >> dri-devel at lists.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
>
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