linux-kernel - Re: [PATCH 6/7] ARM: OMAP: Disable POSTED mode for errata i103 and i767

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Date:	Mon, 25 Nov 2013 14:14:38 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	Joel Fernandes <joelf@...com>
Cc:	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>
Subject: Re: [PATCH 6/7] ARM: OMAP: Disable POSTED mode for errata i103 and
 i767

* Joel Fernandes <joelf@...com> [131125 13:46]:
> Enabling of Posted mode is seen to cause problems on dmtimer modules on AM33xx
> (much like other OMAPs).  Reference discussions on forums [1] [2]. Earlier
> patch solving this on other OMAPs [3].
> 
> For OMAP SoCs with this errata, the fix has been to not enable Posted mode.
> However, on some SoCs (atleast AM33xx) which carry this errata, Posted mode
> is enabled on reset. So we not only need to ignore enabling of the POSTED bit
> when the timer is requested, but also disable Posted mode if errata is present.

This could explain some occasional lost timers I saw a while back when
testing things.. We most likely should merge for the -rc series with cc stable.

Does this depend on the other patches in this series?

Regards,

Tony
 
> [1] http://e2e.ti.com/support/arm/sitara_arm/f/791/t/285744.aspx
> [2] http://e2e.ti.com/support/arm/sitara_arm/f/791/t/270632.aspx
> [3] http://www.spinics.net/lists/linux-omap/msg81770.html
> 
> Reported-by: Russ Dill <russ.dill@...com>
> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
> Signed-off-by: Joel Fernandes <joelf@...com>
> ---
>  arch/arm/plat-omap/include/plat/dmtimer.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/plat-omap/include/plat/dmtimer.h b/arch/arm/plat-omap/include/plat/dmtimer.h
> index fb92abb..2861b15 100644
> --- a/arch/arm/plat-omap/include/plat/dmtimer.h
> +++ b/arch/arm/plat-omap/include/plat/dmtimer.h
> @@ -336,8 +336,11 @@ static inline void __omap_dm_timer_enable_posted(struct omap_dm_timer *timer)
>  	if (timer->posted)
>  		return;
>  
> -	if (timer->errata & OMAP_TIMER_ERRATA_I103_I767)
> +	if (timer->errata & OMAP_TIMER_ERRATA_I103_I767) {
> +		timer->posted = OMAP_TIMER_NONPOSTED;
> +		__omap_dm_timer_write(timer, OMAP_TIMER_IF_CTRL_REG, 0, 0);
>  		return;
> +	}
>  
>  	__omap_dm_timer_write(timer, OMAP_TIMER_IF_CTRL_REG,
>  			      OMAP_TIMER_CTRL_POSTED, 0);
> -- 
> 1.8.1.2
> 
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