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Date: Fri, 07 Nov 2014 12:45:07 +0100 From: Lucas Stach <l.stach@...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>, Philipp Zabel <p.zabel@...gutronix.de>, 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>, 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 Subject: Re: [PATCH V4 5/6] dw-hdmi: add support for multi byte register width access Am Freitag, den 07.11.2014, 19:35 +0800 schrieb Andy Yan: > On rockchip rk3288, only word(32-bit) accesses are > permitted for hdmi registers. Byte width access (writeb, > readb) generates an imprecise external abort. > > Signed-off-by: Andy Yan <andy.yan@...k-chips.com> > --- > drivers/gpu/drm/bridge/dw_hdmi.c | 49 +++++++++++++++++++++++++++++++++++++--- > 1 file changed, 46 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c > index df76a8c..9867642 100644 > --- a/drivers/gpu/drm/bridge/dw_hdmi.c > +++ b/drivers/gpu/drm/bridge/dw_hdmi.c > @@ -126,19 +126,42 @@ struct dw_hdmi { [...] > + 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) { This should throw an error if the property value in devicetree is not recognized. This could be simplified like this: u32 val = 1; // this won't touch val if it can't find the property 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; case 1: hdmi->write = dw_hdmi_writeb; hdmi->read = dw_hdmi_readb; hdmi->reg_shift = 0; break; default: dev_err(dev, "unrecognized value for reg-io-width"); // error handling } Also the DT binding doc for this property is missing. Regards, Lucas -- Pengutronix e.K. | Lucas Stach | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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