[PATCH] spi: nuc900: Fix setting multiple bits settings in register

[PATCH] spi: nuc900: Fix setting multiple bits settings in register

[Axel Lin]

The correct way to set multiple bits settings is always clear these
bit fields before set new settings.

Current code does not cause problem because the reset value of these
bit fields are 0, and these settings only set once during probe.

Signed-off-by: Axel Lin <axel.lin-8E1dMatC8ynQT0dZR+AlfA@public.gmane.org>
---
 drivers/spi/spi-nuc900.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/spi-nuc900.c b/drivers/spi/spi-nuc900.c
index 675c210..16e30de 100644
--- a/drivers/spi/spi-nuc900.c
+++ b/drivers/spi/spi-nuc900.c
@@ -37,7 +37,9 @@
 /* usi register bit */
 #define ENINT		(0x01 << 17)
 #define ENFLG		(0x01 << 16)
+#define SLEEP		(0x0f << 12)
 #define TXNUM		(0x03 << 8)
+#define TXBITLEN	(0x1f << 3)
 #define TXNEG		(0x01 << 2)
 #define RXNEG		(0x01 << 1)
 #define LSB		(0x01 << 10)
@@ -115,19 +117,16 @@ static void nuc900_spi_chipsel(struct spi_device *spi, int value)
 	}
 }
 
-static void nuc900_spi_setup_txnum(struct nuc900_spi *hw,
-							unsigned int txnum)
+static void nuc900_spi_setup_txnum(struct nuc900_spi *hw, unsigned int txnum)
 {
 	unsigned int val;
 	unsigned long flags;
 
 	spin_lock_irqsave(&hw->lock, flags);
 
-	val = __raw_readl(hw->regs + USI_CNT);
+	val = __raw_readl(hw->regs + USI_CNT) & ~TXNUM;
 
-	if (!txnum)
-		val &= ~TXNUM;
-	else
+	if (txnum)
 		val |= txnum << 0x08;
 
 	__raw_writel(val, hw->regs + USI_CNT);
@@ -144,7 +143,7 @@ static void nuc900_spi_setup_txbitlen(struct nuc900_spi *hw,
 
 	spin_lock_irqsave(&hw->lock, flags);
 
-	val = __raw_readl(hw->regs + USI_CNT);
+	val = __raw_readl(hw->regs + USI_CNT) & ~TXBITLEN;
 
 	val |= (txbitlen << 0x03);
 
@@ -283,12 +282,11 @@ static void nuc900_set_sleep(struct nuc900_spi *hw, unsigned int sleep)
 
 	spin_lock_irqsave(&hw->lock, flags);
 
-	val = __raw_readl(hw->regs + USI_CNT);
+	val = __raw_readl(hw->regs + USI_CNT) & ~SLEEP;
 
 	if (sleep)
 		val |= (sleep << 12);
-	else
-		val &= ~(0x0f << 12);
+
 	__raw_writel(val, hw->regs + USI_CNT);
 
 	spin_unlock_irqrestore(&hw->lock, flags);
-- 
1.8.3.2



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Re: [PATCH] spi: nuc900: Fix setting multiple bits settings in register

[Geert Uytterhoeven]

Hi Axel,

On Fri, Mar 21, 2014 at 6:24 AM, Axel Lin <axel.lin-8E1dMatC8ynQT0dZR+AlfA@public.gmane.org> wrote:
> -       val = __raw_readl(hw->regs + USI_CNT);
> +       val = __raw_readl(hw->regs + USI_CNT) & ~TXNUM;
>
> -       if (!txnum)
> -               val &= ~TXNUM;
> -       else
> +       if (txnum)
>                 val |= txnum << 0x08;

I think it's easier to read if you keep the masking and setting together,
and remove the conditional, e.g.

        val = __raw_readl(hw->regs + USI_CNT);
        val = (val & ~TXNUM) | (txnum << 0x08);
        __raw_writel(val, hw->regs + USI_CNT);

Just my personal thoughts, too.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

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                                -- Linus Torvalds
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Re: [PATCH] spi: nuc900: Fix setting multiple bits settings in register

[Mark Brown]

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On Fri, Mar 21, 2014 at 09:13:00AM +0100, Geert Uytterhoeven wrote:

> I think it's easier to read if you keep the masking and setting together,
> and remove the conditional, e.g.

>         val = __raw_readl(hw->regs + USI_CNT);
>         val = (val & ~TXNUM) | (txnum << 0x08);
>         __raw_writel(val, hw->regs + USI_CNT);

> Just my personal thoughts, too.

I agree, that seems clearer.

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Re: [PATCH] spi: nuc900: Fix setting multiple bits settings in register

[Mark Brown]

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On Fri, Mar 21, 2014 at 01:24:14PM +0800, Axel Lin wrote:
> The correct way to set multiple bits settings is always clear these
> bit fields before set new settings.

Applied, thanks.

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