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<base href="https://bugs.freedesktop.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [CHV] Backlight init fails on Surface 3 if module load order is wrong"
href="https://bugs.freedesktop.org/show_bug.cgi?id=96571">96571</a>
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<th>Summary</th>
<td>[CHV] Backlight init fails on Surface 3 if module load order is wrong
</td>
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<th>Product</th>
<td>DRI
</td>
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<th>Version</th>
<td>XOrg git
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>Linux (All)
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
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<th>Component</th>
<td>DRM/Intel
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<th>Assignee</th>
<td>intel-gfx-bugs@lists.freedesktop.org
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<th>Reporter</th>
<td>stephenjust@gmail.com
</td>
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<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
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<th>CC</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr></table>
<p>
<div>
<pre>As stated by Jani in <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [BYT DSI PMIC backlight] Backlight support for Dell Venue 8 Pro"
href="show_bug.cgi?id=85977#c38">https://bugs.freedesktop.org/show_bug.cgi?id=85977#c38</a>, if
i915 is loaded before relevant PMIC/I2C/PWM drivers, PWM backlight probe can
fail.
[drm:pwm_setup_backlight [i915]] *ERROR* Failed to own the pwm chip
It would be nice to have this fixed so that the backlight on Surface 3 might
work reliably on distro-stock kernels that don't build-in certain modules to
influence the probe order.
Quote from <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [BYT DSI PMIC backlight] Backlight support for Dell Venue 8 Pro"
href="show_bug.cgi?id=85977">Bug 85977</a>:
<span class="quote">>There still remains the issue with probe ordering: if i915 gets probed before all >the related pmic/i2c drivers, pwm_get() fails as described in <a href="show_bug.cgi?id=96571#c32">comment #32</a>. If you >want to file a new bug for that, I don't mind.</span >
>
<span class="quote">>As a workaround, these config options worked for me on Surface 3 PMIC backlight:</span >
>
<span class="quote">>CONFIG_PWM=y
>CONFIG_PWM_CRC=y
>CONFIG_I2C_DESIGNWARE_PLATFORM=y
>CONFIG_I2C_DESIGNWARE_PCI=y
>CONFIG_INTEL_SOC_PMIC=y
>CONFIG_DRM_I915=m</span ></pre>
</div>
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