From: Dmitry Osipenko <digetx@gmail.com> To: Thierry Reding <thierry.reding@gmail.com>, Jonathan Hunter <jonathanh@nvidia.com>, David Heidelberg <david@ixit.cz>, Svyatoslav Ryhel <clamor95@gmail.com> Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: [PATCH v1] drm/tegra: dc: Don't set PLL clock to 0Hz Date: Tue, 2 Mar 2021 16:15:06 +0300 [thread overview] Message-ID: <20210302131506.11790-1-digetx@gmail.com> (raw) RGB output doesn't allow to change parent clock rate of the display and PCLK rate is set to 0Hz in this case. The tegra_dc_commit_state() shall not set the display clock to 0Hz since this change propagates to the parent clock. The DISP clock is defined as a NODIV clock by the tegra-clk driver and all NODIV clocks use the CLK_SET_RATE_PARENT flag. This bug stayed unnoticed because by default PLLP is used as the parent clock for the display controller and PLLP silently skips the erroneous 0Hz rate changes because it always has active child clocks that don't permit rate changes. The PLLP isn't acceptable for some devices that we want to upstream (like Samsung Galaxy Tab and ASUS TF700T) due to a display panel clock rate requirements that can't be fulfilled by using PLLP and then the bug pops up in this case since parent clock is set to 0Hz, killing the display output. Don't touch DC clock if pclk=0 in order to fix the problem. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- drivers/gpu/drm/tegra/dc.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c index 1399e4032701..4ecda4cdf345 100644 --- a/drivers/gpu/drm/tegra/dc.c +++ b/drivers/gpu/drm/tegra/dc.c @@ -1723,6 +1723,11 @@ static void tegra_dc_commit_state(struct tegra_dc *dc, dev_err(dc->dev, "failed to set clock rate to %lu Hz\n", state->pclk); + + err = clk_set_rate(dc->clk, state->pclk); + if (err < 0) + dev_err(dc->dev, "failed to set clock %pC to %lu Hz: %d\n", + dc->clk, state->pclk, err); } DRM_DEBUG_KMS("rate: %lu, div: %u\n", clk_get_rate(dc->clk), @@ -1733,11 +1738,6 @@ static void tegra_dc_commit_state(struct tegra_dc *dc, value = SHIFT_CLK_DIVIDER(state->div) | PIXEL_CLK_DIVIDER_PCD1; tegra_dc_writel(dc, value, DC_DISP_DISP_CLOCK_CONTROL); } - - err = clk_set_rate(dc->clk, state->pclk); - if (err < 0) - dev_err(dc->dev, "failed to set clock %pC to %lu Hz: %d\n", - dc->clk, state->pclk, err); } static void tegra_dc_stop(struct tegra_dc *dc) -- 2.29.2
WARNING: multiple messages have this Message-ID (diff)
From: Dmitry Osipenko <digetx@gmail.com> To: Thierry Reding <thierry.reding@gmail.com>, Jonathan Hunter <jonathanh@nvidia.com>, David Heidelberg <david@ixit.cz>, Svyatoslav Ryhel <clamor95@gmail.com> Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: [PATCH v1] drm/tegra: dc: Don't set PLL clock to 0Hz Date: Tue, 2 Mar 2021 16:15:06 +0300 [thread overview] Message-ID: <20210302131506.11790-1-digetx@gmail.com> (raw) RGB output doesn't allow to change parent clock rate of the display and PCLK rate is set to 0Hz in this case. The tegra_dc_commit_state() shall not set the display clock to 0Hz since this change propagates to the parent clock. The DISP clock is defined as a NODIV clock by the tegra-clk driver and all NODIV clocks use the CLK_SET_RATE_PARENT flag. This bug stayed unnoticed because by default PLLP is used as the parent clock for the display controller and PLLP silently skips the erroneous 0Hz rate changes because it always has active child clocks that don't permit rate changes. The PLLP isn't acceptable for some devices that we want to upstream (like Samsung Galaxy Tab and ASUS TF700T) due to a display panel clock rate requirements that can't be fulfilled by using PLLP and then the bug pops up in this case since parent clock is set to 0Hz, killing the display output. Don't touch DC clock if pclk=0 in order to fix the problem. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- drivers/gpu/drm/tegra/dc.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c index 1399e4032701..4ecda4cdf345 100644 --- a/drivers/gpu/drm/tegra/dc.c +++ b/drivers/gpu/drm/tegra/dc.c @@ -1723,6 +1723,11 @@ static void tegra_dc_commit_state(struct tegra_dc *dc, dev_err(dc->dev, "failed to set clock rate to %lu Hz\n", state->pclk); + + err = clk_set_rate(dc->clk, state->pclk); + if (err < 0) + dev_err(dc->dev, "failed to set clock %pC to %lu Hz: %d\n", + dc->clk, state->pclk, err); } DRM_DEBUG_KMS("rate: %lu, div: %u\n", clk_get_rate(dc->clk), @@ -1733,11 +1738,6 @@ static void tegra_dc_commit_state(struct tegra_dc *dc, value = SHIFT_CLK_DIVIDER(state->div) | PIXEL_CLK_DIVIDER_PCD1; tegra_dc_writel(dc, value, DC_DISP_DISP_CLOCK_CONTROL); } - - err = clk_set_rate(dc->clk, state->pclk); - if (err < 0) - dev_err(dc->dev, "failed to set clock %pC to %lu Hz: %d\n", - dc->clk, state->pclk, err); } static void tegra_dc_stop(struct tegra_dc *dc) -- 2.29.2 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
next reply other threads:[~2021-03-03 3:36 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-02 13:15 Dmitry Osipenko [this message] 2021-03-02 13:15 ` [PATCH v1] drm/tegra: dc: Don't set PLL clock to 0Hz Dmitry Osipenko 2021-03-24 15:14 ` Thierry Reding 2021-03-24 15:14 ` Thierry Reding
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