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

[Andy Yan]

Hi Zabel:
On 2014年11月27日 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....@rock-chips.com>

---

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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