[Letux-kernel] [PATCH RFC] w1: omap: disable iclk autoidle

Tony Lindgren tony at atomide.com
Mon Oct 1 16:47:45 CEST 2018


* Andreas Kemnade <andreas at kemnade.info> [180929 22:39]:
> +	 * needed to disable autoidle, if system power state is too low
> +	 * hdq transactions will not work correctly, although registers
> +	 * are accessible.
> +	 * According to AM/DM3730 TRM p.2879 the hwmod has to way to
> +	 * keep iclk running during a transfer if autoidle is enabled

Sounds like hdq1w is not wake-up capable and the uart is blocking
deeper SoC idle states. To me it seems that you should rather just
use pm_qos in the hdq1w driver to block SoC idle for the duration
of transfers.

We had a similar problem with audio playback glitches a while
back, see commit 9834ffd1ecc3 ("ASoC: omap-mcbsp: Add PM QoS
support for McBSP to prevent glitches"). See how it does
pm_qos_add_request(), pm_qos_update_request() and
pm_qos_remove_request().

Regards,

Tony


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