From 0c43f1e02598d304d4cfb06187305445c8207675 Mon Sep 17 00:00:00 2001 From: Tomi Valkeinen Date: Tue, 13 Jun 2017 12:02:10 +0300 Subject: [PATCH] drm/omap: fix i886 work-around 7d267f068a8b4944d52e8b0ae4c8fcc1c1c5c5ba ("drm/omap: work-around for errata i886") changed how the PLL dividers and multipliers are calculated. While the new way should work fine for all the PLLs, it breaks omap5 PLLs. The issues seen are rather odd: seemed that the output clock rate is half of what we asked. It is unclear what's causing there issues. As a work-around this patch adds a "errata_i886" flag, which is set only for DRA7's PLLs, and the PLL setup is done according to that flag. Signed-off-by: Tomi Valkeinen Tested-by: H. Nikolaus Schaller --- drivers/gpu/drm/omapdrm/dss/dss.h | 3 +++ drivers/gpu/drm/omapdrm/dss/pll.c | 29 ++++++++++++++++++++--------- drivers/gpu/drm/omapdrm/dss/video-pll.c | 2 ++ 3 files changed, 25 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/omapdrm/dss/dss.h b/drivers/gpu/drm/omapdrm/dss/dss.h index 0854860..ed46557 100644 --- a/drivers/gpu/drm/omapdrm/dss/dss.h +++ b/drivers/gpu/drm/omapdrm/dss/dss.h @@ -185,6 +185,9 @@ struct dss_pll_hw { bool has_freqsel; bool has_selfreqdco; bool has_refsel; + + /* DRA7 errata i886: use high N & M to avoid jitter */ + bool errata_i886; }; struct dss_pll { diff --git a/drivers/gpu/drm/omapdrm/dss/pll.c b/drivers/gpu/drm/omapdrm/dss/pll.c index 5e22130..9d9d9d4 100644 --- a/drivers/gpu/drm/omapdrm/dss/pll.c +++ b/drivers/gpu/drm/omapdrm/dss/pll.c @@ -215,8 +215,8 @@ bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin, dss_pll_calc_func func, void *data) { const struct dss_pll_hw *hw = pll->hw; - int n, n_min, n_max; - int m, m_min, m_max; + int n, n_start, n_stop, n_inc; + int m, m_start, m_stop, m_inc; unsigned long fint, clkdco; unsigned long pll_hw_max; unsigned long fint_hw_min, fint_hw_max; @@ -226,22 +226,33 @@ bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin, fint_hw_min = hw->fint_min; fint_hw_max = hw->fint_max; - n_min = max(DIV_ROUND_UP(clkin, fint_hw_max), 1ul); - n_max = min((unsigned)(clkin / fint_hw_min), hw->n_max); + n_start = max(DIV_ROUND_UP(clkin, fint_hw_max), 1ul); + n_stop = min((unsigned)(clkin / fint_hw_min), hw->n_max); + n_inc = 1; + + if (hw->errata_i886) { + swap(n_start, n_stop); + n_inc = -1; + } pll_max = pll_max ? pll_max : ULONG_MAX; - /* Try to find high N & M to avoid jitter (DRA7 errata i886) */ - for (n = n_max; n >= n_min; --n) { + for (n = n_start; n != n_stop; n += n_inc) { fint = clkin / n; - m_min = max(DIV_ROUND_UP(DIV_ROUND_UP(pll_min, fint), 2), + m_start = max(DIV_ROUND_UP(DIV_ROUND_UP(pll_min, fint), 2), 1ul); - m_max = min3((unsigned)(pll_max / fint / 2), + m_stop = min3((unsigned)(pll_max / fint / 2), (unsigned)(pll_hw_max / fint / 2), hw->m_max); + m_inc = 1; + + if (hw->errata_i886) { + swap(m_start, m_stop); + m_inc = -1; + } - for (m = m_max; m >= m_min; --m) { + for (m = m_start; m != m_stop; m += m_inc) { clkdco = 2 * m * fint; if (func(n, m, fint, clkdco, data)) diff --git a/drivers/gpu/drm/omapdrm/dss/video-pll.c b/drivers/gpu/drm/omapdrm/dss/video-pll.c index f7ea02a..38a239c 100644 --- a/drivers/gpu/drm/omapdrm/dss/video-pll.c +++ b/drivers/gpu/drm/omapdrm/dss/video-pll.c @@ -130,6 +130,8 @@ static const struct dss_pll_hw dss_dra7_video_pll_hw = { .mX_lsb[3] = 5, .has_refsel = true, + + .errata_i886 = true, }; struct dss_pll *dss_video_pll_init(struct platform_device *pdev, int id, -- 2.7.4