[PATCH v2] clk: bcm2835: De-assert/assert PLL reset signal when appropriate

[PATCH v2] clk: bcm2835: De-assert/assert PLL reset signal when appropriate

[Boris Brezillon]

In order to enable a PLL, not only the PLL has to be powered up and
locked, but you also have to de-assert the reset signal. The last part
was missing. Add it so PLLs that were not enabled by the FW/bootloader
can be enabled from Linux.

Fixes: 41691b8862e2 ("clk: bcm2835: Add support for programming the audio domain clocks")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
---
Changes in v2:
- simplify bcm2835_pll_off()
---
 drivers/clk/bcm/clk-bcm2835.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index a07f6451694a..fa0d5c8611a0 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -602,9 +602,7 @@ static void bcm2835_pll_off(struct clk_hw *hw)
 	const struct bcm2835_pll_data *data = pll->data;
 
 	spin_lock(&cprman->regs_lock);
-	cprman_write(cprman, data->cm_ctrl_reg,
-		     cprman_read(cprman, data->cm_ctrl_reg) |
-		     CM_PLL_ANARST);
+	cprman_write(cprman, data->cm_ctrl_reg, CM_PLL_ANARST);
 	cprman_write(cprman, data->a2w_ctrl_reg,
 		     cprman_read(cprman, data->a2w_ctrl_reg) |
 		     A2W_PLL_CTRL_PWRDN);
@@ -640,6 +638,10 @@ static int bcm2835_pll_on(struct clk_hw *hw)
 		cpu_relax();
 	}
 
+	cprman_write(cprman, data->a2w_ctrl_reg,
+		     cprman_read(cprman, data->a2w_ctrl_reg) |
+		     A2W_PLL_CTRL_PRST_DISABLE);
+
 	return 0;
 }
 
-- 
2.14.1

Re: [PATCH v2] clk: bcm2835: De-assert/assert PLL reset signal when appropriate

[Eric Anholt]

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Boris Brezillon <boris.brezillon@bootlin.com> writes:

> In order to enable a PLL, not only the PLL has to be powered up and
> locked, but you also have to de-assert the reset signal. The last part
> was missing. Add it so PLLs that were not enabled by the FW/bootloader
> can be enabled from Linux.
>
> Fixes: 41691b8862e2 ("clk: bcm2835: Add support for programming the audio domain clocks")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
> ---
> Changes in v2:
> - simplify bcm2835_pll_off()

Reviewed-by: Eric Anholt <eric@anholt.net>

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Re: [PATCH v2] clk: bcm2835: De-assert/assert PLL reset signal when appropriate

[Stephen Boyd]

Quoting Boris Brezillon (2018-03-22 02:11:30)
> In order to enable a PLL, not only the PLL has to be powered up and
> locked, but you also have to de-assert the reset signal. The last part
> was missing. Add it so PLLs that were not enabled by the FW/bootloader
> can be enabled from Linux.
> 
> Fixes: 41691b8862e2 ("clk: bcm2835: Add support for programming the audio domain clocks")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
> ---

Applied to clk-next