linux-kernel - Re: [PATCH v5 1/6] clk: qcom: Add support for SMD-RPM Clocks

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Message-ID: <20151228020809.GB16437@tuxbot>
Date:	Sun, 27 Dec 2015 18:08:09 -0800
From:	Bjorn Andersson <bjorn@...o.se>
To:	Georgi Djakov <georgi.djakov@...aro.org>
Cc:	sboyd@...eaurora.org, agross@...eaurora.org,
	mturquette@...libre.com, linux-clk@...r.kernel.org,
	bjorn.andersson@...ymobile.com, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v5 1/6] clk: qcom: Add support for SMD-RPM Clocks

On Thu 03 Dec 06:02 PST 2015, Georgi Djakov wrote:

> This adds initial support for clocks controlled by the Resource
> Power Manager (RPM) processor on some Qualcomm SoCs, which use
> the qcom_smd_rpm driver to communicate with RPM.
> Such platforms are msm8916, apq8084 and msm8974.
> 
> The RPM is a dedicated hardware engine for managing the shared
> SoC resources in order to keep the lowest power profile. It
> communicates with other hardware subsystems via shared memory
> and accepts clock requests, aggregates the requests and turns
> the clocks on/off or scales them on demand.
> 
> This driver is based on the codeaurora.org driver:
> https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.10/tree/drivers/clk/qcom/clock-rpm.c
> 
> Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>

Hi Georgi,

I added the 8974 clocks to this to make the WNCSS core happy (need
CXO_A2 for XO calibration), but I have a few issues:

*) msm_serial acquires a handle to GCC_BLSP1_UART2_APPS_CLK which is
parented by "xo"; the clock framework returns a clock, as the gcc driver
is probed, but as the rpmcc driver isn't probed clk_get_rate() returns
0.

Do you have any patches in your tree to fix the ordering or making the
clk_get() implement probe deferral in this case?

*) If I let the code call clk_smd_rpm_enable_scaling() my eMMC becomes
very unstable, with a rather high occurrence of timeouts during boot
(like 80% of boots fail to mount my rootfs).

Part of these (unrelated to your code) issues I think this looks good,
and hacking around these two issues allows me to get CXO_A2 ticking :)

Regards,
Bjorn
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