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 <tomi.valkeinen@ti.com>
Tested-by: H. Nikolaus Schaller <hns@goldelico.com>

diff --git a/drivers/gpu/drm/omapdrm/dss/dss.h b/drivers/gpu/drm/omapdrm/dss/dss.h
index 085486024089f997f0580a2a5ab2dd25d7c4be26..ed465572491ea5b6d7814753d033db458878d222 100644 (file)
--- 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 5e221302768bef048ba37c576cd3cd4c93a903cf..9d9d9d42009baf4ee634733ee31a464bbe16e6bd 100644 (file)
--- 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 f7ea02a88b1a80e0380780f9e75c9d12d098d487..38a239cc5e044ece0abe4fcf5bcdad380e414b54 100644 (file)
--- 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,