From mboxrd@z Thu Jan 1 00:00:00 1970
From: daniel.lezcano@linaro.org (Daniel Lezcano)
Date: Wed, 4 Nov 2015 10:46:49 +0100
Subject: [PATCH v2 0/3] let Marvell Berlin SoCs make use of the best delay
timer
In-Reply-To: <1446560917-6318-1-git-send-email-jszhang@marvell.com>
References: <1446560917-6318-1-git-send-email-jszhang@marvell.com>
Message-ID: <5639D409.1030302@linaro.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org
On 11/03/2015 03:28 PM, Jisheng Zhang wrote:
> In case there are several possible delay timers, we purely base the
> selection on the frequency, which is suboptimal in some cases. Take
> one Marvell Berlin platform for example: we have arch timer and dw-apb
> timer. The arch timer freq is 25MHZ while the dw-apb timer freq is
> 100MHZ, current selection would choose the dw-apb timer. But the dw
> apb timer is on the APB bus while arch timer sits in CPU, the cost
> of accessing the apb timer is higher than the arch timer.
>
> This series firstly modifies register_current_timer_delay() to choose
> the highest rating delay timer: use the rating as a primary indication
> and fall back to comparing the frequency if the rating is not set or
> the same. Then we set the arch_delay_timer rating as 400, finally
> Implement ARM delay timer for the dw_apb_timer and set its rating as 300.
Hi Jisheng, Arnd,
I don't feel comfortable with the rating / freq think. I am afraid this
approach based on heuristic will bring a lot of complexity and
workarounds in the code for a small benefit.
Why don't we define a DT entry for the delay timer ? So we delegate the
choice to the platform DT definition.
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