[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....@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


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