[PATCH V4 5/6] dw-hdmi: add support for multi byte register width access

[Lucas Stach]

Am Freitag, den 07.11.2014, 19:35 +0800 schrieb Andy Yan:
> On rockchip rk3288, only word(32-bit) accesses are
> permitted for hdmi registers.  Byte width access (writeb,
> readb) generates an imprecise external abort.
> 
> Signed-off-by: Andy Yan <andy.yan at rock-chips.com>
> ---
>  drivers/gpu/drm/bridge/dw_hdmi.c | 49 
> +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 46 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c 
> b/drivers/gpu/drm/bridge/dw_hdmi.c
> index df76a8c..9867642 100644
> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> @@ -126,19 +126,42 @@ struct dw_hdmi {
[...]
> +     u32 val;
> +
> +     if (!of_property_read_u32(np, "reg-io-width", &val)) {
> +             switch (val) {
> +             case 4:
> +                     hdmi->write = dw_hdmi_writel;
> +                     hdmi->read = dw_hdmi_readl;
> +                     hdmi->reg_shift = 2;
> +                     break;
> +             default:
> +                     hdmi->write = dw_hdmi_writeb;
> +                     hdmi->read = dw_hdmi_readb;
> +                     hdmi->reg_shift = 0;
> +                     break;
> +             }
> +     } else {
> +             hdmi->write = dw_hdmi_writeb;
> +             hdmi->read = dw_hdmi_readb;
> +             hdmi->reg_shift = 0;
> +     }
>  
>       ddc_node = of_parse_phandle(np, "ddc-i2c-bus", 0);
>       if (ddc_node) {

This should throw an error if the property value in devicetree is not
recognized. This could be simplified like this:

        u32 val = 1;

        // this won't touch val if it can't find the property
        of_property_read_u32(np, "reg-io-width", &val) 


        switch (val) {
        case 4:
                hdmi->write = dw_hdmi_writel;
                hdmi->read = dw_hdmi_readl;
                hdmi->reg_shift = 2;
                break;
        case 1:
                hdmi->write = dw_hdmi_writeb;
                hdmi->read = dw_hdmi_readb;
                hdmi->reg_shift = 0;
                break;
        default:
                dev_err(dev, "unrecognized value for reg-io-width");
                // error handling
        }

Also the DT binding doc for this property is missing.

Regards,
Lucas
-- 
Pengutronix e.K.             | Lucas Stach                 |
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