[PATCH libdrm v3] modetest: Add support for setting mode having floating vertical refresh rate

[Devarsh Thakkar <devarsh.thakkar@xxxxxxxxxx>]

For the scenario where user may require to modeset with a mode
supporting a fractional value for vertical refresh-rate,
appropriate mode can be selected by searching for mode
having matching fractional vertical refresh rate using
below equation.

vrefresh = (1000 * pixel clock) / (htotal * vtotal) Hz.

We do this way since driver doesn't return float value of vrefresh
as it use int for vrefresh in struct drm_mode_info, but we can derive
the actual value using pixel clock, horizontal total size and
vertical total size values.

So for e.g. if user want to select mode having 59.94 Hz as refresh rate
then with this patch it be can done as shown in below command,
given there is an appropriate mode is available :

modetest -M xlnx -s 39:1920x1080-59.94@BG24 -v

NOTE: Above command was tested on xilinx DRM driver with DP
monitor which was supporting mode having 59.94 Hz refresh rate.

Signed-off-by: Devarsh Thakkar <devarsh.thakkar@xxxxxxxxxx>
---
V2: Update commit message
V3: Update with below changes as per review comments :
  1) Use epsilon for vrefresh comparison
  2) Use implicit type-casting wherever possible
---
 tests/modetest/modetest.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/tests/modetest/modetest.c b/tests/modetest/modetest.c
index e66be66..b4edfcb 100644
--- a/tests/modetest/modetest.c
+++ b/tests/modetest/modetest.c
@@ -54,6 +54,7 @@
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
 #endif
+#include <math.h>

 #include "xf86drm.h"
 #include "xf86drmMode.h"
@@ -795,7 +796,7 @@ struct pipe_arg {
        uint32_t crtc_id;
        char mode_str[64];
        char format_str[5];
-       unsigned int vrefresh;
+       float vrefresh;
        unsigned int fourcc;
        drmModeModeInfo *mode;
        struct crtc *crtc;
@@ -822,11 +823,12 @@ struct plane_arg {

 static drmModeModeInfo *
 connector_find_mode(struct device *dev, uint32_t con_id, const char *mode_str,
-        const unsigned int vrefresh)
+       const float vrefresh)
 {
        drmModeConnector *connector;
        drmModeModeInfo *mode;
        int i;
+       float mode_vrefresh;

        connector = get_connector_by_id(dev, con_id);
        if (!connector || !connector->count_modes)
@@ -839,9 +841,11 @@ connector_find_mode(struct device *dev, uint32_t con_id, const char *mode_str,
                         * first mode that match with the name. Else, return the mode that match
                         * the name and the specified vertical refresh frequency.
                         */
+                       mode_vrefresh = mode->clock * 1000.00
+                                       / (mode->htotal * mode->vtotal);
                        if (vrefresh == 0)
                                return mode;
-                       else if (mode->vrefresh == vrefresh)
+                       else if (fabs(mode_vrefresh - vrefresh) < 0.005)
                                return mode;
                }
        }
@@ -1393,8 +1397,8 @@ static void atomic_set_mode(struct device *dev, struct pipe_arg *pipes, unsigned
                if (pipe->mode == NULL)
                        continue;

-               printf("setting mode %s-%dHz on connectors ",
-                      pipe->mode_str, pipe->mode->vrefresh);
+               printf("setting mode %s-%.2fHz on connectors ",
+                      pipe->mode_str, pipe->vrefresh);
                for (j = 0; j < pipe->num_cons; ++j) {
                        printf("%s, ", pipe->cons[j]);
                        add_property(dev, pipe->con_ids[j], "CRTC_ID", pipe->crtc->crtc->crtc_id);
@@ -1476,8 +1480,8 @@ static void set_mode(struct device *dev, struct pipe_arg *pipes, unsigned int co
                if (pipe->mode == NULL)
                        continue;

-               printf("setting mode %s-%dHz@%s on connectors ",
-                      pipe->mode_str, pipe->mode->vrefresh, pipe->format_str);
+               printf("setting mode %s-%.2fHz@%s on connectors ",
+                      pipe->mode_str, pipe->vrefresh, pipe->format_str);
                for (j = 0; j < pipe->num_cons; ++j)
                        printf("%s, ", pipe->cons[j]);
                printf("crtc %d\n", pipe->crtc->crtc->crtc_id);
@@ -1713,7 +1717,7 @@ static int parse_connector(struct pipe_arg *pipe, const char *arg)
        pipe->mode_str[len] = '\0';

        if (*p == '-') {
-               pipe->vrefresh = strtoul(p + 1, &endp, 10);
+               pipe->vrefresh = strtof(p + 1, &endp);
                p = endp;
        }

--
2.7.4

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