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Fri, 3 Jun 2022 04:24:18 -0400 (EDT) Date: Fri, 3 Jun 2022 10:24:16 +0200 From: Maxime Ripard To: Roman Stratiienko Cc: wens@csie.org, jernej.skrabec@gmail.com, airlied@linux.ie, daniel@ffwll.ch, samuel@sholland.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, megi@xff.cz Subject: Re: [PATCH] drm/sun4i: sun8i: Add the ability to keep scaler enabled for VI layer Message-ID: <20220603082416.ukohug3mwzu43csu@penduick> References: <20220602180118.66170-1-r.stratiienko@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220602180118.66170-1-r.stratiienko@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220603_012428_046010_C18F7DC3 X-CRM114-Status: GOOD ( 23.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Thu, Jun 02, 2022 at 06:01:18PM +0000, Roman Stratiienko wrote: > According to DE2.0/DE3.0 manual VI scaler enable register is double > buffered, but de facto it doesn't, or the hardware has the shadow > register latching issues which causes single-frame picture corruption > after changing the state of scaler enable register. > > Allow the user to keep the scaler always enabled, preventing the UI > glitches on the transition from scaled to unscaled state. > > NOTE: > UI layer scaler has more registers with double-buffering issue and can't > be workarounded in the same manner. > > You may find a python test and a demo video for this issue at [1] > > [1]: https://github.com/GloDroid/glodroid_tests/issues/4 Please describe the issue entirely here. The commit log must be self-sufficient. > Signed-off-by: Roman Stratiienko > --- > drivers/gpu/drm/sun4i/sun8i_mixer.c | 12 ++++++++++++ > drivers/gpu/drm/sun4i/sun8i_vi_layer.c | 4 +++- > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c b/drivers/gpu/drm/sun4i/sun8i_mixer.c > index 71ab0a00b4de..15cad0330f66 100644 > --- a/drivers/gpu/drm/sun4i/sun8i_mixer.c > +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c > @@ -27,6 +27,18 @@ > #include "sun8i_vi_layer.h" > #include "sunxi_engine.h" > > +/* According to DE2.0/DE3.0 manual VI scaler enable register is double > + * buffered, but de facto it doesn't, or the hardware has the shadow > + * register latching issues which causes single-frame picture corruption > + * after changing the state of scaler enable register. > + * Allow the user to keep the scaler always enabled, preventing the UI > + * glitches on the transition from scaled to unscaled state. > + */ > +int sun8i_vi_keep_scaler_enabled; > +MODULE_PARM_DESC(keep_vi_scaler_enabled, > + "Keep VI scaler enabled (1 = enabled, 0 = disabled (default))"); > +module_param_named(keep_vi_scaler_enabled, sun8i_vi_keep_scaler_enabled, int, 0644); > + It's not clear to me why we would want to make that a parameter? If it never works, we should fix it once and for all and not allow a broken setup at all. Maxime _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel