[PATCH V3 3/4] dw-hdmi: add support for multi byte register width access

[Andy Yan]

On rockchip rk3288, only word(32-bit) accesses are
permitted for hdmi registers.  Byte width access (writeb,
readb) generate an imprecise external abort.

Signed-off-by: Andy Yan <andy.yan at rock-chips.com>
---
 drivers/gpu/drm/bridge/dw_hdmi.c | 53 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 48 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index e561286..a34f928 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -126,19 +126,42 @@ struct dw_hdmi {
 
 	unsigned int sample_rate;
 	int ratio;
+	void (*write)(u8 val, void __iomem *addr);
+	u8 (*read)(void __iomem *addr);
+	int reg_shift;
 };
 
+static void dw_hdmi_writel(u8 val, void __iomem *addr)
+{
+	writel(val, addr);
+}
+
+static u8 dw_hdmi_readl(void __iomem *addr)
+{
+	return readl(addr);
+}
+
+static void dw_hdmi_writeb(u8 val, void __iomem *addr)
+{
+	writeb(val, addr);
+}
+
+static u8 dw_hdmi_readb(void __iomem *addr)
+{
+	return readb(addr);
+}
+
 static inline void hdmi_writeb(struct dw_hdmi *hdmi, u8 val, int offset)
 {
-	writeb(val, hdmi->regs + offset);
+	hdmi->write(val, hdmi->regs + (offset << hdmi->reg_shift));
 }
 
 static inline u8 hdmi_readb(struct dw_hdmi *hdmi, int offset)
 {
-	return readb(hdmi->regs + offset);
+	return hdmi->read(hdmi->regs + (offset << hdmi->reg_shift));
 }
 
-static void hdmi_modb(struct dw_hdmi *hdmi, u8 data, u8 mask, unsigned reg)
+static void hdmi_modb(struct dw_hdmi *hdmi, u32 data, u32 mask, unsigned reg)
 {
 	u8 val = hdmi_readb(hdmi, reg) & ~mask;
 
@@ -146,8 +169,8 @@ static void hdmi_modb(struct dw_hdmi *hdmi, u8 data, u8 mask, unsigned reg)
 	hdmi_writeb(hdmi, val, reg);
 }
 
-static void hdmi_mask_writeb(struct dw_hdmi *hdmi, u8 data, unsigned int reg,
-		      u8 shift, u8 mask)
+static void hdmi_mask_writeb(struct dw_hdmi *hdmi, u32 data, unsigned int reg,
+		      u32 shift, u32 mask)
 {
 	hdmi_modb(hdmi, data << shift, mask, reg);
 }
@@ -1500,6 +1523,26 @@ 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;
+
+	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) {
-- 
1.9.1