Date:   Fri, 11 Feb 2022 09:30:43 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <Kavyasree.Kotagiri@...rochip.com>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>,
        <robh+dt@...nel.org>, <lee.jones@...aro.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <UNGLinuxDriver@...rochip.com>, <Manohar.Puri@...rochip.com>
Subject: Re: [PATCH 2/2] mfd: atmel-flexcom: Add support for lan966 flexcom
 shared configurations

On 10.02.2022 09:45, Kavyasree Kotagiri wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Each flexcom of LAN966 SoC has 2 chip selects. For each chip
> select of each flexcom there is a configuration register
> FLEXCOM_SHARED[0-4]:SS_MASK[0-1]. The width of configuration
> register is 21 because there are 21 shared pins on each of
> which the chip select can be mapped. Each bit of the register
> represents a different FLEXCOM_SHARED pin.

Hi Kavyasree,

I may have wrongly understood but it seems to me like you have a little pin
controller (mapped at a different address than flexcom itself) that
connects to each flexcom chip selects (and maybe to other IPs CSs). In that
case, in my opinion, it would be best to model the pin controller with a
GPIO driver (examples in drivers/gpio) and to pass to flexcom only one
binding something like:

cs-gpios = <&your_pin_controller pin_number state>;

and to do proper GPIO handling in flexcom with GPIO APIs.

Thank you,
Claudiu Beznea

> 
> Signed-off-by: Kavyasree Kotagiri <kavyasree.kotagiri@...rochip.com>
> ---
>  drivers/mfd/atmel-flexcom.c | 49 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
> 
> diff --git a/drivers/mfd/atmel-flexcom.c b/drivers/mfd/atmel-flexcom.c
> index 559eb4d352b6..b8fc476e411d 100644
> --- a/drivers/mfd/atmel-flexcom.c
> +++ b/drivers/mfd/atmel-flexcom.c
> @@ -27,6 +27,12 @@
>  #define FLEX_MR_OPMODE_MASK    (0x3 << FLEX_MR_OPMODE_OFFSET)
>  #define FLEX_MR_OPMODE(opmode) (((opmode) << FLEX_MR_OPMODE_OFFSET) &  \
>                                  FLEX_MR_OPMODE_MASK)
> +#ifdef CONFIG_SOC_LAN966
> +/* LAN966 register offsets */
> +#define FLEX_SHRD_SS_MASK_0 0x0
> +#define FLEX_SHRD_SS_MASK_1 0x4
> +#define FLEX_SHRD_MASK      0x1FFFFF
> +#endif
> 
>  struct atmel_flexcom {
>         void __iomem *base;
> @@ -39,6 +45,10 @@ static int atmel_flexcom_probe(struct platform_device *pdev)
>         struct device_node *np = pdev->dev.of_node;
>         struct resource *res;
>         struct atmel_flexcom *ddata;
> +#ifdef CONFIG_SOC_LAN966
> +       u32 lan966x_ss_pin, lan966x_cs, val;
> +       void __iomem *shared_base;
> +#endif
>         int err;
> 
>         ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
> @@ -76,6 +86,45 @@ static int atmel_flexcom_probe(struct platform_device *pdev)
>          */
>         writel(FLEX_MR_OPMODE(ddata->opmode), ddata->base + FLEX_MR);
> 
> +#ifdef CONFIG_SOC_LAN966
> +       /*
> +        * Flexcom Shared Register Configurations:
> +        * In order to map chip select index X of Flexcom Y to FLEXCOM_SHARED Z,
> +        * write 0 to bit index Z of FLEXCOM_SHARED[Y]:SS_MASK[X].
> +        */
> +       if (of_property_read_bool(np, "lan966x-flx-shared-cfg")) {
> +               /* Shared pin */
> +               err = of_property_read_u32(np, "lan966x-ss-pin", &lan966x_ss_pin);
> +               if (err)
> +                       return err;
> +
> +               if (lan966x_ss_pin > 20)
> +                       return -EINVAL;
> +
> +               /* chip-select */
> +               err = of_property_read_u32(np, "lan966x-cs", &lan966x_cs);
> +               if (err)
> +                       return err;
> +
> +               if (lan966x_cs > 1)
> +                       return -EINVAL;
> +
> +               shared_base = devm_ioremap_resource(&pdev->dev,
> +                               platform_get_resource(pdev, IORESOURCE_MEM, 1));
> +               if (IS_ERR(shared_base)) {
> +                       dev_dbg(&pdev->dev, "No Flexcom shared register config\n");
> +                       return PTR_ERR(shared_base);
> +               }
> +
> +               val = ~(1 << lan966x_ss_pin) & FLEX_SHRD_MASK;
> +
> +               if (lan966x_cs == 0)
> +                       writel(val, shared_base + FLEX_SHRD_SS_MASK_0);
> +               else
> +                       writel(val, shared_base + FLEX_SHRD_SS_MASK_1);
> +       }
> +#endif
> +
>         clk_disable_unprepare(ddata->clk);
> 
>         return devm_of_platform_populate(&pdev->dev);
> --
> 2.17.1
> 
> 
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