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Subject: Re: [PATCH v8 01/21] pinctrl: tegra: Fix write barrier placement in
 pmx_writel
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com, tglx@linutronix.de,
        jason@lakedaemon.net, marc.zyngier@arm.com,
        linus.walleij@linaro.org, stefan@agner.ch, mark.rutland@arm.com
Cc:     pdeschrijver@nvidia.com, pgaikwad@nvidia.com, sboyd@kernel.org,
        linux-clk@vger.kernel.org, linux-gpio@vger.kernel.org,
        jckuo@nvidia.com, josephl@nvidia.com, talho@nvidia.com,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        mperttunen@nvidia.com, spatra@nvidia.com, robh+dt@kernel.org,
        devicetree@vger.kernel.org, rjw@rjwysocki.net,
        viresh.kumar@linaro.org, linux-pm@vger.kernel.org
References: <1565308020-31952-1-git-send-email-skomatineni@nvidia.com>
 <1565308020-31952-2-git-send-email-skomatineni@nvidia.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <a8b0c979-de6f-16d0-5e46-436a1a6ced8c@gmail.com>
Date:   Fri, 9 Aug 2019 14:38:54 +0300
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09.08.2019 2:46, Sowjanya Komatineni пишет:
> pmx_writel uses writel which inserts write barrier before the
> register write rather.
> 
> This patch has fix to replace writel with writel_relaxed followed
> by a write barrier to ensure write operation before the barrier
> is completed for successful pinctrl change.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
>  drivers/pinctrl/tegra/pinctrl-tegra.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/tegra/pinctrl-tegra.c b/drivers/pinctrl/tegra/pinctrl-tegra.c
> index e3a237534281..982ee634b3b1 100644
> --- a/drivers/pinctrl/tegra/pinctrl-tegra.c
> +++ b/drivers/pinctrl/tegra/pinctrl-tegra.c
> @@ -32,7 +32,9 @@ static inline u32 pmx_readl(struct tegra_pmx *pmx, u32 bank, u32 reg)
>  
>  static inline void pmx_writel(struct tegra_pmx *pmx, u32 val, u32 bank, u32 reg)
>  {
> -	writel(val, pmx->regs[bank] + reg);
> +	writel_relaxed(val, pmx->regs[bank] + reg);
> +	/* make sure pinmux register write completed */
> +	wmb();
>  }
>  
>  static int tegra_pinctrl_get_groups_count(struct pinctrl_dev *pctldev)
> 

But this only ensures that CPU have sent the write to the APB BUS and
not that the write actually taken into effect? I'm a bit paranoid when
it comes to a cross-domain synchronization things.

Any ways it looks better than it was before.

Reviewed-by: Dmitry Osipenko <digetx@gmail.com>