linux-kernel - Re: [PATCH v2 3/3] misc: aspeed-lpc-ctrl: Enable FWH and A2H bridge cycles

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Date:   Tue, 20 Feb 2018 10:19:53 +1100
From:   Cyril Bur <cyrilbur@...il.com>
To:     Joel Stanley <joel@....id.au>, Lee Jones <lee.jones@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andrew Jeffery <andrew@...id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Ryan Chen <ryan_chen@...eedtech.com>,
        Lei YU <mine260309@...il.com>
Subject: Re: [PATCH v2 3/3] misc: aspeed-lpc-ctrl: Enable FWH and A2H bridge
 cycles

On Mon, 2018-02-19 at 17:54 +1030, Joel Stanley wrote:
> To date this driver has relied on prevous state from out of tree hacks
> and vendor u-boot trees in order to have the host be able to access
> data over the LPC bus.
> 
> Now we explicitly enable the AHB to LPC bridge and FWH cycles from when
> the user first configures the address to map. We chose to do this then
> as before that time there is no way for the kernel to know where it is
> safe to point the LPC window.
> 
> Tested-by: Lei YU <mine260309@...il.com>
> Reviewed-by: Andrew Jeffery <andrew@...id.au>
> Signed-off-by: Joel Stanley <joel@....id.au>

Reviewed-by: Cyril Bur <cyrilbur@...il.com>

> ---
>  drivers/misc/aspeed-lpc-ctrl.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/aspeed-lpc-ctrl.c b/drivers/misc/aspeed-lpc-ctrl.c
> index 1827b7aa6674..a024f8042259 100644
> --- a/drivers/misc/aspeed-lpc-ctrl.c
> +++ b/drivers/misc/aspeed-lpc-ctrl.c
> @@ -21,6 +21,10 @@
>  
>  #define DEVICE_NAME	"aspeed-lpc-ctrl"
>  
> +#define HICR5 0x0
> +#define HICR5_ENL2H	BIT(8)
> +#define HICR5_ENFWH	BIT(10)
> +
>  #define HICR7 0x8
>  #define HICR8 0xc
>  
> @@ -155,8 +159,18 @@ static long aspeed_lpc_ctrl_ioctl(struct file *file, unsigned int cmd,
>  		if (rc)
>  			return rc;
>  
> -		return regmap_write(lpc_ctrl->regmap, HICR8,
> -			(~(map.size - 1)) | ((map.size >> 16) - 1));
> +		rc = regmap_write(lpc_ctrl->regmap, HICR8,
> +				(~(map.size - 1)) | ((map.size >> 16) - 1));
> +		if (rc)
> +			return rc;
> +
> +		/*
> +		 * Enable LPC FHW cycles. This is required for the host to
> +		 * access the regions specified.
> +		 */
> +		return regmap_update_bits(lpc_ctrl->regmap, HICR5,
> +				HICR5_ENFWH | HICR5_ENL2H,
> +				HICR5_ENFWH | HICR5_ENL2H);
>  	}
>  
>  	return -EINVAL;