linux-kernel - [PATCH v1 3/5] PM / devfreq: tegra20: Use clk_round_rate

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Date:   Tue, 31 Mar 2020 02:16:15 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-clk@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 3/5] PM / devfreq: tegra20: Use clk_round_rate_unboundly()

The clk_round_rate() doesn't work for us properly if clock rate is bounded
by a min/max rate that is requested by some other clk-user because we're
building devfreq's OPP table based on the rounding.

In particular this becomes a problem if display driver is probed earlier
than devfreq, and thus, display adds a memory bandwidth request using
interconnect API, which results in a minimum clock-rate being set for
the memory clk. In a result, the lowest devfreq OPP rate is getting
limited to the minimum rate imposed by the display driver.

Let's use new clk_round_rate_unboundly() that resolves the problem by
rounding clock rate without taking into account min/max limits imposed by
active clk users.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/devfreq/tegra20-devfreq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/devfreq/tegra20-devfreq.c b/drivers/devfreq/tegra20-devfreq.c
index ff82bac9ee4e..1bb10ef11dfe 100644
--- a/drivers/devfreq/tegra20-devfreq.c
+++ b/drivers/devfreq/tegra20-devfreq.c
@@ -149,10 +149,10 @@ static int tegra_devfreq_probe(struct platform_device *pdev)

 	tegra->regs = mc->regs;

-	max_rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
+	max_rate = clk_round_rate_unboundly(tegra->emc_clock, ULONG_MAX);

 	for (rate = 0; rate <= max_rate; rate++) {
-		rate = clk_round_rate(tegra->emc_clock, rate);
+		rate = clk_round_rate_unboundly(tegra->emc_clock, rate);

 		err = dev_pm_opp_add(&pdev->dev, rate, 0);
 		if (err) {
-- 
2.25.1