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([2001:861:44c0:66c0:d284:de3f:b3d6:f714]) by smtp.gmail.com with ESMTPSA id o1sm20351064wru.91.2021.11.09.05.33.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Nov 2021 05:33:32 -0800 (PST) Subject: Re: [PATCH] drm/omap: increase DSS5 max tv pclk to 192MHz To: tomba@kernel.org Cc: linux-omap@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, khilman@baylibre.com, Tomi Valkeinen References: <20211012133939.2145462-1-narmstrong@baylibre.com> From: Neil Armstrong Organization: Baylibre Message-ID: Date: Tue, 9 Nov 2021 14:33:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20211012133939.2145462-1-narmstrong@baylibre.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tomi, On 12/10/2021 15:39, Neil Armstrong wrote: > From: Tomi Valkeinen > > DSS5's maximum tv pclk rate (i.e. HDMI) is set to 186MHz, which comes > from the TRM (DPLL_HDMI_CLK1 frequency must be lower than 186 MHz). To > support DRA76's wide screen HDMI feature, we need to increase this > maximum rate. > > Testing shows that the PLL seems to work fine even with ~240MHz clocks, > and even the HDMI output at that clock is stable enough for monitors to > show a picture. This holds true for all DRA7 and AM5 SoCs (and probably > also for OMAP5). > > However, the highest we can go without big refactoring to the clocking > code is 192MHz, as that is the DSS func clock we get from the PRCM. So, > increase the max HDMI pixel clock to 192MHz for now, to allow some more > 2k+ modes to work. > > This patch never had a clear confirmation from HW people, but this > change stayed on production trees for multiple years without any report > on an eventual breakage. > > Signed-off-by: Tomi Valkeinen > Signed-off-by: Neil Armstrong > --- > drivers/gpu/drm/omapdrm/dss/dispc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Tomi, > > I slighly changed the commit message to point the fact this patch has been > used in production fort years without any sign of breakage. > > Neil > > diff --git a/drivers/gpu/drm/omapdrm/dss/dispc.c b/drivers/gpu/drm/omapdrm/dss/dispc.c > index 5619420cc2cc..3c4a4991e45a 100644 > --- a/drivers/gpu/drm/omapdrm/dss/dispc.c > +++ b/drivers/gpu/drm/omapdrm/dss/dispc.c > @@ -4458,7 +4458,7 @@ static const struct dispc_features omap54xx_dispc_feats = { > .mgr_width_max = 4096, > .mgr_height_max = 4096, > .max_lcd_pclk = 170000000, > - .max_tv_pclk = 186000000, > + .max_tv_pclk = 192000000, > .max_downscale = 4, > .max_line_width = 2048, > .min_pcd = 1, > > base-commit: e4e737bb5c170df6135a127739a9e6148ee3da82 > Gentle ping, Neil