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

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Message-ID: <1417019657.3177.10.camel@pengutronix.de>
Date:	Wed, 26 Nov 2014 17:34:17 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Andy Yan <andy.yan@...k-chips.com>
Cc:	airlied@...ux.ie, heiko@...ech.de, fabio.estevam@...escale.com,
	rmk+kernel@....linux.org.uk,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Shawn Guo <shawn.guo@...aro.org>,
	Josh Boyer <jwboyer@...hat.com>,
	Sean Paul <seanpaul@...omium.org>,
	Inki Dae <inki.dae@...sung.com>,
	Dave Airlie <airlied@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	Lucas Stach <l.stach@...gutronix.de>,
	Zubair.Kakakhel@...tec.com, djkurtz@...gle.com, ykk@...k-chips.com,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	devel@...verdev.osuosl.org, devicetree@...r.kernel.org,
	linux-rockchip@...ts.infradead.org, jay.xu@...k-chips.com,
	Pawel Moll <pawel.moll@....com>, mark.yao@...k-chips.com,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH v13 07/12] drm: bridge/dw_hdmi: add support for
 multi-byte register width access

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@...k-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.

>  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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