fbdev: sh_mobile_hdmi: add support for more precise HDMI clock configuration

The HDMI clock has to be reconfigured for different video modes. However, the
precision of the supplying SoC clock on SH-Mobile systems is often
insufficient. This patch allows to additionally reconfigure the parent clock
to achieve the optimal HDMI clock frequency, in case this is supported by the
platform.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 68 insertions, 44 deletions

diff --git a/drivers/video/sh_mobile_hdmi.c b/drivers/video/sh_mobile_hdmi.c
index d7df10315d8d..ef41c215abae 100644
--- a/drivers/video/sh_mobile_hdmi.c
+++ b/drivers/video/sh_mobile_hdmi.c
@@ -685,11 +685,21 @@ static void sh_hdmi_configure(struct sh_hdmi *hdmi)
 }
 
 static unsigned long sh_hdmi_rate_error(struct sh_hdmi *hdmi,
-                                        const struct fb_videomode *mode)
+                const struct fb_videomode *mode,
+                unsigned long *hdmi_rate, unsigned long *parent_rate)
 {
-        long target = PICOS2KHZ(mode->pixclock) * 1000,
-                rate = clk_round_rate(hdmi->hdmi_clk, target);
-        unsigned long rate_error = rate > 0 ? abs(rate - target) : ULONG_MAX;
+        unsigned long target = PICOS2KHZ(mode->pixclock) * 1000, rate_error;
+        struct sh_mobile_hdmi_info *pdata = hdmi->dev->platform_data;
+
+        *hdmi_rate = clk_round_rate(hdmi->hdmi_clk, target);
+        if ((long)*hdmi_rate < 0)
+                *hdmi_rate = clk_get_rate(hdmi->hdmi_clk);
+
+        rate_error = (long)*hdmi_rate > 0 ? abs(*hdmi_rate - target) : ULONG_MAX;
+        if (rate_error && pdata->clk_optimize_parent)
+                rate_error = pdata->clk_optimize_parent(target, hdmi_rate, parent_rate);
+        else if (clk_get_parent(hdmi->hdmi_clk))
+                *parent_rate = clk_get_rate(clk_get_parent(hdmi->hdmi_clk));
 
         dev_dbg(hdmi->dev, "%u-%u-%u-%u x %u-%u-%u-%u\n",
                 mode->left_margin, mode->xres,
@@ -697,14 +707,15 @@ static unsigned long sh_hdmi_rate_error(struct sh_hdmi *hdmi,
                 mode->upper_margin, mode->yres,
                 mode->lower_margin, mode->vsync_len);
 
-        dev_dbg(hdmi->dev, "\t@%lu(+/-%lu)Hz, e=%lu / 1000, r=%uHz\n", target,
-                 rate_error, rate_error ? 10000 / (10 * target / rate_error) : 0,
-                 mode->refresh);
+        dev_dbg(hdmi->dev, "\t@%lu(+/-%lu)Hz, e=%lu / 1000, r=%uHz, p=%luHz\n", target,
+                rate_error, rate_error ? 10000 / (10 * target / rate_error) : 0,
+                mode->refresh, *parent_rate);
 
         return rate_error;
 }
 
-static int sh_hdmi_read_edid(struct sh_hdmi *hdmi)
+static int sh_hdmi_read_edid(struct sh_hdmi *hdmi, unsigned long *hdmi_rate,
+                             unsigned long *parent_rate)
 {
         struct fb_var_screeninfo tmpvar;
         struct fb_var_screeninfo *var = &tmpvar;
@@ -754,11 +765,14 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi)
         for (i = 0, mode = hdmi->monspec.modedb;
              f_width && f_height && i < hdmi->monspec.modedb_len && !exact_match;
              i++, mode++) {
-                unsigned long rate_error = sh_hdmi_rate_error(hdmi, mode);
+                unsigned long rate_error;
 
                 /* No interest in unmatching modes */
                 if (f_width != mode->xres || f_height != mode->yres)
                         continue;
+
+                rate_error = sh_hdmi_rate_error(hdmi, mode, hdmi_rate, parent_rate);
+
                 if (f_refresh == mode->refresh || (!f_refresh && !rate_error))
                         /*
                          * Exact match if either the refresh rate matches or it
@@ -802,7 +816,7 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi)
 
                 if (modelist) {
                         found = &modelist->mode;
-                        found_rate_error = sh_hdmi_rate_error(hdmi, found);
+                        found_rate_error = sh_hdmi_rate_error(hdmi, found, hdmi_rate, parent_rate);
                 }
         }
 
@@ -810,10 +824,6 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi)
         if (!found)
                 return -ENXIO;
 
-        dev_info(hdmi->dev, "Using %s mode %ux%u@%uHz (%luHz), clock error %luHz\n",
-                 modelist ? "default" : "EDID", found->xres, found->yres,
-                 found->refresh, PICOS2KHZ(found->pixclock) * 1000, found_rate_error);
-
         if ((found->xres == 720 && found->yres == 480) ||
             (found->xres == 1280 && found->yres == 720) ||
             (found->xres == 1920 && found->yres == 1080))
@@ -821,6 +831,11 @@ static int sh_hdmi_read_edid(struct sh_hdmi *hdmi)
         else
                 hdmi->preprogrammed_mode = false;
 
+        dev_dbg(hdmi->dev, "Using %s %s mode %ux%u@%uHz (%luHz), clock error %luHz\n",
+                modelist ? "default" : "EDID", hdmi->preprogrammed_mode ? "VIC" : "external",
+                found->xres, found->yres, found->refresh,
+                PICOS2KHZ(found->pixclock) * 1000, found_rate_error);
+
         fb_videomode_to_var(&hdmi->var, found);
         sh_hdmi_external_video_param(hdmi);
 
@@ -972,39 +987,38 @@ static bool sh_hdmi_must_reconfigure(struct sh_hdmi *hdmi)
 
 /**
  * sh_hdmi_clk_configure() - set HDMI clock frequency and enable the clock
- * @hdmi:       driver context
- * @pixclock:   pixel clock period in picoseconds
- * return:      configured positive rate if successful
- *              0 if couldn't set the rate, but managed to enable the clock
- *              negative error, if couldn't enable the clock
+ * @hdmi:               driver context
+ * @hdmi_rate:          HDMI clock frequency in Hz
+ * @parent_rate:        if != 0 - set parent clock rate for optimal precision
+ * return:              configured positive rate if successful
+ *                      0 if couldn't set the rate, but managed to enable the
+ *                      clock, negative error, if couldn't enable the clock
  */
-static long sh_hdmi_clk_configure(struct sh_hdmi *hdmi, unsigned long pixclock)
+static long sh_hdmi_clk_configure(struct sh_hdmi *hdmi, unsigned long hdmi_rate,
+                                  unsigned long parent_rate)
 {
-        long rate;
+        struct sh_mobile_hdmi_info *pdata = hdmi->dev->platform_data;
         int ret;
 
-        rate = PICOS2KHZ(pixclock) * 1000;
-        rate = clk_round_rate(hdmi->hdmi_clk, rate);
-        if (rate > 0) {
-                ret = clk_set_rate(hdmi->hdmi_clk, rate);
+        if (parent_rate && clk_get_parent(hdmi->hdmi_clk)) {
+                ret = clk_set_rate(clk_get_parent(hdmi->hdmi_clk), parent_rate);
                 if (ret < 0) {
-                        dev_warn(hdmi->dev, "Cannot set rate %ld: %d\n", rate, ret);
-                        rate = 0;
+                        dev_warn(hdmi->dev, "Cannot set parent rate %ld: %d\n", parent_rate, ret);
+                        hdmi_rate = clk_round_rate(hdmi->hdmi_clk, hdmi_rate);
                 } else {
-                        dev_dbg(hdmi->dev, "HDMI set frequency %lu\n", rate);
+                        dev_dbg(hdmi->dev, "HDMI set parent frequency %lu\n", parent_rate);
                 }
-        } else {
-                rate = 0;
-                dev_warn(hdmi->dev, "Cannot get suitable rate: %ld\n", rate);
         }
 
-        ret = clk_enable(hdmi->hdmi_clk);
+        ret = clk_set_rate(hdmi->hdmi_clk, hdmi_rate);
         if (ret < 0) {
-                dev_err(hdmi->dev, "Cannot enable clock: %d\n", ret);
-                return ret;
+                dev_warn(hdmi->dev, "Cannot set rate %ld: %d\n", hdmi_rate, ret);
+                hdmi_rate = 0;
+        } else {
+                dev_dbg(hdmi->dev, "HDMI set frequency %lu\n", hdmi_rate);
         }
 
-        return rate;
+        return hdmi_rate;
 }
 
 /* Hotplug interrupt occurred, read EDID */
@@ -1024,16 +1038,17 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)
         mutex_lock(&hdmi->mutex);
 
         if (hdmi->hp_state == HDMI_HOTPLUG_EDID_DONE) {
+                unsigned long parent_rate = 0, hdmi_rate;
+
                 /* A device has been plugged in */
                 pm_runtime_get_sync(hdmi->dev);
 
-                ret = sh_hdmi_read_edid(hdmi);
+                ret = sh_hdmi_read_edid(hdmi, &hdmi_rate, &parent_rate);
                 if (ret < 0)
                         goto out;
 
                 /* Reconfigure the clock */
-                clk_disable(hdmi->hdmi_clk);
-                ret = sh_hdmi_clk_configure(hdmi, hdmi->var.pixclock);
+                ret = sh_hdmi_clk_configure(hdmi, hdmi_rate, parent_rate);
                 if (ret < 0)
                         goto out;
 
@@ -1166,13 +1181,22 @@ static int __init sh_hdmi_probe(struct platform_device *pdev)
                 goto egetclk;
         }
 
-        /* Some arbitrary relaxed pixclock just to get things started */
-        rate = sh_hdmi_clk_configure(hdmi, 37037);
+        /* An arbitrary relaxed pixclock just to get things started: from standard 480p */
+        rate = clk_round_rate(hdmi->hdmi_clk, PICOS2KHZ(37037));
+        if (rate > 0)
+                rate = sh_hdmi_clk_configure(hdmi, rate, 0);
+
         if (rate < 0) {
                 ret = rate;
                 goto erate;
         }
 
+        ret = clk_enable(hdmi->hdmi_clk);
+        if (ret < 0) {
+                dev_err(hdmi->dev, "Cannot enable clock: %d\n", ret);
+                goto erate;
+        }
+
         dev_dbg(&pdev->dev, "Enabled HDMI clock at %luHz\n", rate);
 
         if (!request_mem_region(res->start, resource_size(res), dev_name(&pdev->dev))) {
@@ -1190,10 +1214,6 @@ static int __init sh_hdmi_probe(struct platform_device *pdev)
 
         platform_set_drvdata(pdev, hdmi);
 
-        /* Product and revision IDs are 0 in sh-mobile version */
-        dev_info(&pdev->dev, "Detected HDMI controller 0x%x:0x%x\n",
-                 hdmi_read(hdmi, HDMI_PRODUCT_ID), hdmi_read(hdmi, HDMI_REVISION_ID));
-
         /* Set up LCDC callbacks */
         board_cfg = &pdata->lcd_chan->board_cfg;
         board_cfg->owner = THIS_MODULE;
@@ -1206,6 +1226,10 @@ static int __init sh_hdmi_probe(struct platform_device *pdev)
         pm_runtime_enable(&pdev->dev);
         pm_runtime_resume(&pdev->dev);
 
+        /* Product and revision IDs are 0 in sh-mobile version */
+        dev_info(&pdev->dev, "Detected HDMI controller 0x%x:0x%x\n",
+                 hdmi_read(hdmi, HDMI_PRODUCT_ID), hdmi_read(hdmi, HDMI_REVISION_ID));
+
         ret = request_irq(irq, sh_hdmi_hotplug, 0,
                           dev_name(&pdev->dev), hdmi);
         if (ret < 0) {