linux-kernel - [PATCH 1/2] clk: bcm2835: Fix setting of PLL divider clock rates

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Message-Id: <1455591838-22725-1-git-send-email-eric@anholt.net>
Date:	Mon, 15 Feb 2016 19:03:57 -0800
From:	Eric Anholt <eric@...olt.net>
To:	linux-clk@...r.kernel.org
Cc:	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee@...nel.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Mike Turquette <mturquette@...libre.com>,
	Eric Anholt <eric@...olt.net>, stable@...r.kernel.org
Subject: [PATCH 1/2] clk: bcm2835: Fix setting of PLL divider clock rates

Our dividers weren't being set successfully because CM_PASSWORD wasn't
included in the register write.  It looks easier to just compute the
divider to write ourselves than to update clk-divider for the ability
to OR in some arbitrary bits on write.

Fixes about half of the video modes on my HDMI monitor (everything
except 720x400).

Cc: stable@...r.kernel.org
Signed-off-by: Eric Anholt <eric@...olt.net>
---
 drivers/clk/bcm/clk-bcm2835.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 015e687..9f4df8f 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1107,13 +1107,15 @@ static int bcm2835_pll_divider_set_rate(struct clk_hw *hw,
 	struct bcm2835_pll_divider *divider = bcm2835_pll_divider_from_hw(hw);
 	struct bcm2835_cprman *cprman = divider->cprman;
 	const struct bcm2835_pll_divider_data *data = divider->data;
-	u32 cm;
-	int ret;
+	u32 cm, div, max_div = 1 << A2W_PLL_DIV_BITS;
 
-	ret = clk_divider_ops.set_rate(hw, rate, parent_rate);
-	if (ret)
-		return ret;
+	div = DIV_ROUND_UP_ULL(parent_rate, rate);
+
+	div = min(div, max_div);
+	if (div == max_div)
+		div = 0;
 
+	cprman_write(cprman, data->a2w_reg, div);
 	cm = cprman_read(cprman, data->cm_reg);
 	cprman_write(cprman, data->cm_reg, cm | data->load_mask);
 	cprman_write(cprman, data->cm_reg, cm & ~data->load_mask);
-- 
2.7.0