[PATCH v8 6/9] drm: bridge/dw_hdmi: add support for multi byte register width access

[Andy Yan <andy.yan@rock-chips.com>]

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@rock-chips.com>

---

Changes in v8: None
Changes in v7: None
Changes in v6:
- move some modification to  patch#6
- 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

Changes in v2: None

 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 e9f0dfe..978c709 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -101,6 +101,11 @@ struct hdmi_data_info {
 	struct hdmi_vmode video_mode;
 };
 
+union dw_reg_ptr {
+	u32 __iomem *p32;
+	u8 __iomem *p8;
+};
+
 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;
 
 	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);
+}
+
+static u8 dw_hdmi_readl(struct dw_hdmi *hdmi, int offset)
+{
+	return readl(hdmi->regs.p32 + offset);
+}
+
+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)
@@ -1499,6 +1527,23 @@ static int dw_hdmi_bind(struct device *dev, struct device *master, void *data)
 	struct device_node *ddc_node;
 	struct resource *iores;
 	int ret, irq;
+	u32 val = 1;
+
+	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) {
@@ -1525,9 +1570,9 @@ static int dw_hdmi_bind(struct device *dev, struct device *master, void *data)
 		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);
 
 	if (hdmi->plat_data->setup)
 		hdmi->priv = hdmi->plat_data->setup(pdev);
-- 
1.9.1