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Subject[PATCH] drm/stm: ltdc: use crtc_mode_fixup to update adjusted_mode clock
Date
There is a difference between the panel/bridge requested pixel clock
value and the real one due to the hw platform clock preciseness (pll,
dividers...). This patch updates the adjusted_mode clock value with
the real hw clock value so then attached encoder & connector can use
it for precise timing computations.

Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
---
drivers/gpu/drm/stm/ltdc.c | 35 +++++++++++++++++++++++++----------
1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index b48589343ae1..90b3de516c91 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -428,12 +428,35 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR);
}

+static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc,
+ const struct drm_display_mode *mode,
+ struct drm_display_mode *adjusted_mode)
+{
+ struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+ int rate = mode->clock * 1000;
+
+ /*
+ * TODO clk_round_rate() does not work yet. When ready, it can
+ * be used instead of clk_set_rate() then clk_get_rate().
+ */
+
+ clk_disable(ldev->pixel_clk);
+ if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
+ DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
+ return false;
+ }
+ clk_enable(ldev->pixel_clk);
+
+ adjusted_mode->clock = clk_get_rate(ldev->pixel_clk) / 1000;
+
+ return true;
+}
+
static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
{
struct ltdc_device *ldev = crtc_to_ltdc(crtc);
struct drm_display_mode *mode = &crtc->state->adjusted_mode;
struct videomode vm;
- int rate = mode->clock * 1000;
u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
u32 total_width, total_height;
u32 val;
@@ -456,15 +479,6 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
total_width = accum_act_w + vm.hfront_porch;
total_height = accum_act_h + vm.vfront_porch;

- clk_disable(ldev->pixel_clk);
-
- if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
- DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
- return;
- }
-
- clk_enable(ldev->pixel_clk);
-
/* Configures the HS, VS, DE and PC polarities. Default Active Low */
val = 0;

@@ -528,6 +542,7 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc,
}

static const struct drm_crtc_helper_funcs ltdc_crtc_helper_funcs = {
+ .mode_fixup = ltdc_crtc_mode_fixup,
.mode_set_nofb = ltdc_crtc_mode_set_nofb,
.atomic_flush = ltdc_crtc_atomic_flush,
.atomic_enable = ltdc_crtc_atomic_enable,
--
2.15.1
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