Re: [PATCH v13 07/12] drm: bridge/dw_hdmi: add support for multi-byte register width access

[Andy Yan]

Hi Zabel:
On 2014å11æ27æ 00:34, Philipp Zabel wrote:
> Am Mittwoch, den 26.11.2014, 21:32 +0800 schrieb Andy Yan:
> > On rockchip rk3288, only word(32-bit) accesses are
> > permitted for hdmi registers.  Byte width accesses (writeb,
> > readb) generate an imprecise external abort.
> >
> > Signed-off-by: Andy Yan <andy.yan@xxxxxxxxxxxxxx>
> >
> > ---
> >
> > Changes in v13: None
> > Changes in v12: None
> > Changes in v11: None
> > Changes in v10: None
> > Changes in v9: None
> > Changes in v8: None
> > Changes in v7: None
> > Changes in v6:
> > - refactor register access without reg_shift
> >
> > Changes in v5:
> > - refactor reg-io-width
> >
> > Changes in v4: None
> > Changes in v3:
> > - split multi-register access to one indepent patch
> >
> >   drivers/gpu/drm/bridge/dw_hdmi.c | 57 +++++++++++++++++++++++++++++++++++-----
> >   1 file changed, 51 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
> > index a53bf63..5e88c8d 100644
> > --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> > +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> > @@ -100,6 +100,11 @@ struct hdmi_data_info {
> >   	struct hdmi_vmode video_mode;
> >   };
> >   
> > +union dw_reg_ptr {
> > +	u32 __iomem *p32;
> > +	u8 __iomem *p8;
> > +};
> I see no need to introduce this. Just explicitly multiply the offset in
> dw_hdmi_writel.
    Is there any disadvantage to do like this?
    The compiler can help us do the explicitly multiply by this way.
> >   struct dw_hdmi {
> >   	struct drm_connector connector;
> >   	struct drm_encoder *encoder;
> > @@ -121,20 +126,43 @@ struct dw_hdmi {
> >   
> >   	struct regmap *regmap;
> >   	struct i2c_adapter *ddc;
> > -	void __iomem *regs;
> > +	union dw_reg_ptr regs;
> Keep this as void __iomem *
>
> >   	unsigned int sample_rate;
> >   	int ratio;
> > +
> > +	void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
> > +	u8 (*read)(struct dw_hdmi *hdmi, int offset);
> >   };
> >   
> > +static void dw_hdmi_writel(struct dw_hdmi *hdmi, u8 val, int offset)
> > +{
> > +	writel(val, hdmi->regs.p32 + offset);
> hdmi->regs + 4 * offset
>
> > +}
> > +
> > +static u8 dw_hdmi_readl(struct dw_hdmi *hdmi, int offset)
> > +{
> > +	return readl(hdmi->regs.p32 + offset);
> same here
>
> > +}
> > +
> > +static void dw_hdmi_writeb(struct dw_hdmi *hdmi, u8 val, int offset)
> > +{
> > +	writeb(val, hdmi->regs.p8 + offset);
> > +}
> > +
> > +static u8 dw_hdmi_readb(struct dw_hdmi *hdmi, int offset)
> > +{
> > +	return readb(hdmi->regs.p8 + offset);
> > +}
> > +
> >   static inline void hdmi_writeb(struct dw_hdmi *hdmi, u8 val, int offset)
> >   {
> > -	writeb(val, hdmi->regs + offset);
> > +	hdmi->write(hdmi, val, offset);
> >   }
> >   
> >   static inline u8 hdmi_readb(struct dw_hdmi *hdmi, int offset)
> >   {
> > -	return readb(hdmi->regs + offset);
> > +	return hdmi->read(hdmi, offset);
> >   }
> >
> >   static void hdmi_modb(struct dw_hdmi *hdmi, u8 data, u8 mask, unsigned reg)
> > @@ -1508,6 +1536,7 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
> >   	struct dw_hdmi *hdmi;
> >   	struct resource *iores;
> >   	int ret, irq;
> > +	u32 val = 1;
> >   
> >   	hdmi = devm_kzalloc(&pdev->dev, sizeof(*hdmi), GFP_KERNEL);
> >   	if (!hdmi)
> > @@ -1520,6 +1549,22 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
> >   	hdmi->ratio = 100;
> >   	hdmi->encoder = encoder;
> >   
> > +	of_property_read_u32(np, "reg-io-width", &val);
> > +
> > +	switch (val) {
> > +	case 4:
> > +		hdmi->write = dw_hdmi_writel;
> > +		hdmi->read = dw_hdmi_readl;
> > +		break;
> > +	case 1:
> > +		hdmi->write = dw_hdmi_writeb;
> > +		hdmi->read = dw_hdmi_readb;
> > +		break;
> > +	default:
> > +		dev_err(dev, "reg-io-width must be 1 or 4\n");
> > +		return -EINVAL;
> > +	}
> > +
> >   	ddc_node = of_parse_phandle(np, "ddc-i2c-bus", 0);
> >   	if (ddc_node) {
> >   		hdmi->ddc = of_find_i2c_adapter_by_node(ddc_node);
> > @@ -1544,9 +1589,9 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
> >   		return ret;
> >   
> >   	iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > -	hdmi->regs = devm_ioremap_resource(dev, iores);
> > -	if (IS_ERR(hdmi->regs))
> > -		return PTR_ERR(hdmi->regs);
> > +	hdmi->regs.p32 = devm_ioremap_resource(dev, iores);
> > +	if (IS_ERR(hdmi->regs.p32))
> > +		return PTR_ERR(hdmi->regs.p32);
> >   
> >   	/* Product and revision IDs */
> >   	dev_info(dev,
> regards
> Philipp

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