From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Yan Subject: Re: [PATCH v13 07/12] drm: bridge/dw_hdmi: add support for multi-byte register width access Date: Mon, 01 Dec 2014 20:46:36 +0800 Message-ID: <547C632C.7000309@rock-chips.com> References: <1417008157-31861-1-git-send-email-andy.yan@rock-chips.com> <1417008759-32257-1-git-send-email-andy.yan@rock-chips.com> <1417019657.3177.10.camel@pengutronix.de> <547843B9.6000806@rock-chips.com> <1417435456.4624.12.camel@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; Format="flowed" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <1417435456.4624.12.camel@pengutronix.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" To: Philipp Zabel Cc: Mark Rutland , heiko@sntech.de, airlied@linux.ie, dri-devel@lists.freedesktop.org, ykk@rock-chips.com, devel@driverdev.osuosl.org, Arnd Bergmann , linux-rockchip@lists.infradead.org, Grant Likely , rmk+kernel@arm.linux.org.uk, jay.xu@rock-chips.com, devicetree@vger.kernel.org, Zubair.Kakakhel@imgtec.com, Pawel Moll , Ian Campbell , Inki Dae , Rob Herring , Sean Paul , Dave Airlie , mark.yao@rock-chips.com, fabio.estevam@freescale.com, Josh Boyer , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, djkurtz@google.com, Kumar Gala , Shawn Guo , Lucas Stach List-Id: devicetree@vger.kernel.org SGkgUGhpbGlwcDoKT24gMjAxNOW5tDEy5pyIMDHml6UgMjA6MDQsIFBoaWxpcHAgWmFiZWwgd3Jv dGU6Cj4gQW0gRnJlaXRhZywgZGVuIDI4LjExLjIwMTQsIDE3OjQzICswODAwIHNjaHJpZWIgQW5k eSBZYW46Cj4+IEhpIFphYmVsOgo+PiBPbiAyMDE05bm0MTHmnIgyN+aXpSAwMDozNCwgUGhpbGlw cCBaYWJlbCB3cm90ZToKPj4+IEFtIE1pdHR3b2NoLCBkZW4gMjYuMTEuMjAxNCwgMjE6MzIgKzA4 MDAgc2NocmllYiBBbmR5IFlhbjoKPj4+PiBPbiByb2NrY2hpcCByazMyODgsIG9ubHkgd29yZCgz Mi1iaXQpIGFjY2Vzc2VzIGFyZQo+Pj4+IHBlcm1pdHRlZCBmb3IgaGRtaSByZWdpc3RlcnMuICBC eXRlIHdpZHRoIGFjY2Vzc2VzICh3cml0ZWIsCj4+Pj4gcmVhZGIpIGdlbmVyYXRlIGFuIGltcHJl 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Lm9yZwpodHRwOi8vZHJpdmVyZGV2LmxpbnV4ZHJpdmVycHJvamVjdC5vcmcvbWFpbG1hbi9saXN0 aW5mby9kcml2ZXJkZXYtZGV2ZWwK From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753573AbaLAMqs (ORCPT ); Mon, 1 Dec 2014 07:46:48 -0500 Received: from lucky1.263xmail.com ([211.157.147.131]:58061 "EHLO lucky1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752922AbaLAMqq (ORCPT ); Mon, 1 Dec 2014 07:46:46 -0500 X-263anti-spam: KSV:0; X-MAIL-GRAY: 1 X-MAIL-DELIVERY: 0 X-KSVirus-check: 0 X-ABS-CHECKED: 4 X-RL-SENDER: andy.yan@rock-chips.com X-FST-TO: l.stach@pengutronix.de X-SENDER-IP: 121.15.173.1 X-LOGIN-NAME: andy.yan@rock-chips.com X-UNIQUE-TAG: <6f55435382ce65c6d86fa34593eb244d> X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Message-ID: <547C632C.7000309@rock-chips.com> Date: Mon, 01 Dec 2014 20:46:36 +0800 From: Andy Yan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Philipp Zabel CC: Mark Rutland , heiko@sntech.de, airlied@linux.ie, dri-devel@lists.freedesktop.org, ykk@rock-chips.com, devel@driverdev.osuosl.org, Pawel Moll , linux-rockchip@lists.infradead.org, Grant Likely , Dave Airlie , jay.xu@rock-chips.com, devicetree@vger.kernel.org, Zubair.Kakakhel@imgtec.com, Arnd Bergmann , Ian Campbell , Inki Dae , Rob Herring , Sean Paul , rmk+kernel@arm.linux.org.uk, mark.yao@rock-chips.com, fabio.estevam@freescale.com, Josh Boyer , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, djkurtz@google.com, Kumar Gala , Shawn Guo , Lucas Stach Subject: Re: [PATCH v13 07/12] drm: bridge/dw_hdmi: add support for multi-byte register width access References: <1417008157-31861-1-git-send-email-andy.yan@rock-chips.com> <1417008759-32257-1-git-send-email-andy.yan@rock-chips.com> <1417019657.3177.10.camel@pengutronix.de> <547843B9.6000806@rock-chips.com> <1417435456.4624.12.camel@pengutronix.de> In-Reply-To: <1417435456.4624.12.camel@pengutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Philipp: On 2014年12月01日 20:04, Philipp Zabel wrote: > Am Freitag, den 28.11.2014, 17:43 +0800 schrieb 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 >>>> >>>> --- >>>> >>>> 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. > Four additional lines, a new defined type, a few more changes to struct > dw_hdmi and dw_hdmi_bind necessary. > > Technically I see no problem to let the compiler do the multiplication, > my issue is that it ever so slightly obfuscates the code. Instead of > just writing "* 4" in two functions, we get a new union that you need to > know about when looking at struct dw_hdmi and dw_hdmi_bind, regs.p8 is > used but never assigned directly, it's just a tiny bit of additional > effort needed to understand the code. But when the cost to avoid that is > so small... > > regards > Philipp > What you said is right, I will change it in PATCH V15 thanks . > _______________________________________________ > Linux-rockchip mailing list > Linux-rockchip@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-rockchip