linux-kernel - Re: [PATCH] drm: tilcdc: add a workaround for failed clk_set

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Date:   Wed, 28 Sep 2016 14:55:18 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
CC:     Jyri Sarha <jsarha@...com>, David Airlie <airlied@...ux.ie>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-drm <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>, Sekhar Nori <nsekhar@...com>
Subject: Re: [PATCH] drm: tilcdc: add a workaround for failed clk_set_rate()

On 28/09/16 14:43, Bartosz Golaszewski wrote:

> how far is far enough to emit a warning? On da850 the requested rate
> is 228000000 Hz, while the calculated divider is 6, which results in
> the real rate of 225000000 Hz. This is less than 1% difference -
> should we take this value as reference?

Good question, and I don't have a clear answer. But I think the point is
just to inform the user that it's likely that his LCD won't work
properly, and often LCDs are quite tolerant about the pclk. So diff less
than 1% is just fine. Even 5% sounds still fine to me, perhaps even 10%.
I think we just have to try something out, and adjust it if people get
the message too often.

 Tomi



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