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authorRobin Murphy <robin.murphy@arm.com>2019-05-17 17:37:22 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-25 11:36:53 +0800
commit1268f8b6b7910abf334200c9c1afa773b25c6874 (patch)
parent301f9d04c5909193b564718f7330ffae50b27eef (diff)
drm/arm/hdlcd: Allow a bit of clock tolerance
[ Upstream commit 1c810739097fdeb31b393b67a0a1e3d7ffdd9f63 ] On the Arm Juno platform, the HDLCD pixel clock is constrained to 250KHz resolution in order to avoid the tiny System Control Processor spending aeons trying to calculate exact PLL coefficients. This means that modes like my oddball 1600x1200 with 130.89MHz clock get rejected since the rate cannot be matched exactly. In practice, though, this mode works quite happily with the clock at 131MHz, so let's relax the check to allow a little bit of slop. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Liviu Dudau <liviu.dudau@arm.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
index 4a108660cc8f..6f03700a94be 100644
--- a/drivers/gpu/drm/arm/hdlcd_crtc.c
+++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
@@ -193,7 +193,8 @@ static enum drm_mode_status hdlcd_crtc_mode_valid(struct drm_crtc *crtc,
long rate, clk_rate = mode->clock * 1000;
rate = clk_round_rate(hdlcd->clk, clk_rate);
- if (rate != clk_rate) {
+ /* 0.1% seems a close enough tolerance for the TDA19988 on Juno */
+ if (abs(rate - clk_rate) * 1000 > clk_rate) {
/* clock required by mode not supported by hardware */