linux-kernel - [PATCH v4 2/2] soc/tegra: pmc: Remove unnecessary memory barrier

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Message-Id: <20190804202927.15014-2-digetx@gmail.com>
Date:   Sun,  4 Aug 2019 23:29:27 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/2] soc/tegra: pmc: Remove unnecessary memory barrier

The removed barrier isn't needed because the writes/reads are strictly
ordered and even if PMC had separate ports for the writes, it wouldn't
matter since the hardware logic takes into effect after triggering CPU's
power-gating and at that point all CPU accesses are guaranteed to be
completed. Hence remove the barrier to eliminate the confusion.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---

Changelog:

v4: No changes.

v3: No changes.

v2: New patch that was added after Jon's Hunter pointing that it's better
    not to change the barrier's placement in the code. In fact the barrier
    is not needed at all.

 drivers/soc/tegra/pmc.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
index 4e44943d0b26..8f8fb2db064d 100644
--- a/drivers/soc/tegra/pmc.c
+++ b/drivers/soc/tegra/pmc.c
@@ -1460,8 +1460,6 @@ void tegra_pmc_enter_suspend_mode(enum tegra_suspend_mode mode)
 	do_div(ticks, USEC_PER_SEC);
 	tegra_pmc_writel(pmc, ticks, PMC_CPUPWROFF_TIMER);
 
-	wmb();
-
 	value = tegra_pmc_readl(pmc, PMC_CNTRL);
 	value &= ~PMC_CNTRL_SIDE_EFFECT_LP0;
 	value |= PMC_CNTRL_CPU_PWRREQ_OE;
-- 
2.22.0