date:   Wed, 01 Feb 2017 10:58:43 +0000
from:   "Peter Senna Tschudin" <peter.senna@...labora.co.uk>
to:     "Archit Taneja" <architt@...eaurora.org>
cc:     ijc+devicetree@...lion.org.uk,
        "Fabio Estevam" <fabio.estevam@....com>, treding@...dia.com,
        linux-kernel@...r.kernel.org, davem@...emloft.net,
        mark.rutland@....com, ykk@...k-chips.com, martin.donnelly@...com,
        mchehab@....samsung.com, robh+dt@...nel.org, galak@...eaurora.org,
        peter.senna@...il.com, pawel.moll@....com, javier@...hile0.org,
        gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
        shawnguo@...nel.org,
        "Peter Senna Tschudin" <peter.senna@...labora.com>, tiwai@...e.com,
        linux@...ck-us.net, martyn.welch@...labora.co.uk,
        rmk+kernel@...linux.org.uk, kernel@...gutronix.de,
        daniel.vetter@...ll.ch, jslaby@...e.cz, devicetree@...r.kernel.org,
        linux@...linux.org.uk, linux-arm-kernel@...ts.infradead.org,
        enric.balletbo@...labora.com, dri-devel@...ts.freedesktop.org,
        "Jani Nikula" <jani.nikula@...ux.intel.com>
subject: Re: [PATCH V7 3/4] drm/bridge: Add driver for GE B850v3 
 LVDS/DP++ Bridge

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

> 
> 
> On 01/30/2017 10:35 PM, Jani Nikula wrote:
> > On Sat, 28 Jan 2017, Peter Senna Tschudin <peter.senna@...labora.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@...ts.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> 
> -- 
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
 
 
 
 

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