linux-kernel - Re: [PATCH 1/4] ARM: rockchip: rk3288: Switch to use the proper PWM IP

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Message-ID: <CAPz6YkW5RVb=Uqgh1hVG5GEftQE9gFy-2EuOCemBVCn=95O4uQ@mail.gmail.com>
Date:	Mon, 18 Aug 2014 10:11:46 -0700
From:	Sonny Rao <sonnyrao@...omium.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Heiko Stuebner <heiko@...ech.de>,
	Thierry Reding <thierry.reding@...il.com>,
	Caesar Wang <caesar.wang@...k-chips.com>,
	Olof Johansson <olof@...om.net>,
	Eddie Cai <eddie.cai@...k-chips.com>,
	Russell King <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] ARM: rockchip: rk3288: Switch to use the proper PWM IP

On Mon, Aug 18, 2014 at 10:09 AM, Doug Anderson <dianders@...omium.org> wrote:
> The rk3288 SoC has an option to switch all of the PWMs in the system
> between the old IP block and the new IP block.  The new IP block is
> working and tested and the suggested PWM to use, so setup the SoC to
> use it and then we can pretend that the other IP block doesn't exist.
>
> This code could go lots of other places, but we've put it here.  Why?
> - Pushing it to the bootloader just makes the code harder to update in
>   the field.  If we later find a bug in the new IP block and want to
>   change our mind about what to use we want it to be easy to update.
> - Putting this code in the driver for IP block is a lot of extra work,
>   device tree bindings, etc.  Now that the new IP block is validated
>   it's likely no future SoCs will need this code.  Why pollute the PWM
>   driver with this?  This is an rk3288 thing so it should be in rk3288
>   code.
> - There's a single bit that switches over PWMs, which makes it extra
>   hard to put this under the PWM device tree nodes.
>
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
>  arch/arm/mach-rockchip/rockchip.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/arch/arm/mach-rockchip/rockchip.c b/arch/arm/mach-rockchip/rockchip.c
> index 8ab9e0e..99133b9 100644
> --- a/arch/arm/mach-rockchip/rockchip.c
> +++ b/arch/arm/mach-rockchip/rockchip.c
> @@ -24,6 +24,24 @@
>  #include <asm/hardware/cache-l2x0.h>
>  #include "core.h"
>
> +static void __init rk3288_init_machine(void)
> +{
> +       void *grf = ioremap(0xff770000, 0x10000);

Is it worth checking for failure here?  Will the system boot without this?

> +
> +       /* Set pwm_sel to RK design PWM in GRF_SOC_CON2; affects all PWMs */
> +       writel(0x00010001, grf + 0x24c);
> +
> +       iounmap(grf);
> +}
> +
> +static void __init rockchip_init_machine(void)
> +{
> +       if (of_machine_is_compatible("rockchip,rk3288"))
> +               rk3288_init_machine();
> +
> +       of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
> +}
> +
>  static const char * const rockchip_board_dt_compat[] = {
>         "rockchip,rk2928",
>         "rockchip,rk3066a",
> @@ -34,6 +52,7 @@ static const char * const rockchip_board_dt_compat[] = {
>  };
>
>  DT_MACHINE_START(ROCKCHIP_DT, "Rockchip Cortex-A9 (Device Tree)")
> +       .init_machine   = rockchip_init_machine,
>         .l2c_aux_val    = 0,
>         .l2c_aux_mask   = ~0,
>         .dt_compat      = rockchip_board_dt_compat,
> --
> 2.1.0.rc2.206.gedb03e5
>
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