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Subject[PATCH 1/2] drm/arm/hdlcd: Actually validate CRTC modes
Date
Rather than allowing any old mode through, then subsequently refusing
unmatchable clock rates in atomic_check when it's too late to back out
and pick a different mode, let's do that validation up-front where it
will cause unsupported modes to be correctly pruned in the first place.

This also eliminates an issue whereby a perceived clock rate of 0 would
cause atomic disable to fail and prevent the module from being unloaded.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

This supersedes my previous patch here:
https://patchwork.freedesktop.org/patch/288553/
---
drivers/gpu/drm/arm/hdlcd_crtc.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
index 0b2b62f8fa3c..ecac6fe0b213 100644
--- a/drivers/gpu/drm/arm/hdlcd_crtc.c
+++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
@@ -186,20 +186,19 @@ static void hdlcd_crtc_atomic_disable(struct drm_crtc *crtc,
clk_disable_unprepare(hdlcd->clk);
}

-static int hdlcd_crtc_atomic_check(struct drm_crtc *crtc,
- struct drm_crtc_state *state)
+static enum drm_mode_status hdlcd_crtc_mode_valid(struct drm_crtc *crtc,
+ const struct drm_display_mode *mode)
{
struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
- struct drm_display_mode *mode = &state->adjusted_mode;
long rate, clk_rate = mode->clock * 1000;

rate = clk_round_rate(hdlcd->clk, clk_rate);
if (rate != clk_rate) {
/* clock required by mode not supported by hardware */
- return -EINVAL;
+ return MODE_NOCLOCK;
}

- return 0;
+ return MODE_OK;
}

static void hdlcd_crtc_atomic_begin(struct drm_crtc *crtc,
@@ -220,7 +219,7 @@ static void hdlcd_crtc_atomic_begin(struct drm_crtc *crtc,
}

static const struct drm_crtc_helper_funcs hdlcd_crtc_helper_funcs = {
- .atomic_check = hdlcd_crtc_atomic_check,
+ .mode_valid = hdlcd_crtc_mode_valid,
.atomic_begin = hdlcd_crtc_atomic_begin,
.atomic_enable = hdlcd_crtc_atomic_enable,
.atomic_disable = hdlcd_crtc_atomic_disable,
--
2.21.0.dirty
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