[PATCH] staging: sm750fb: Simplify M2XCLK divisor encoding

[PATCH] staging: sm750fb: Simplify M2XCLK divisor encoding

[himanshu bakshi]

Replace the switch statement with a macro to encode the M2XCLK
divisor in the corresponding register bits.

This is my first Linux kernel patch.

Signed-off-by: himanshu bakshi <himanshu.bakshi478@gmail.com>
---
 drivers/staging/sm750fb/ddk750_chip.c | 18 +++---------------
 drivers/staging/sm750fb/ddk750_reg.h  |  5 +----
 2 files changed, 4 insertions(+), 19 deletions(-)

diff --git a/drivers/staging/sm750fb/ddk750_chip.c b/drivers/staging/sm750fb/ddk750_chip.c
index aa78d0bc1..2cb849dea 100644
--- a/drivers/staging/sm750fb/ddk750_chip.c
+++ b/drivers/staging/sm750fb/ddk750_chip.c
@@ -109,21 +109,9 @@ static void set_memory_clock(unsigned int frequency)
 
 	/* Set the corresponding divisor in the register. */
 	reg = peek32(CURRENT_GATE) & ~CURRENT_GATE_M2XCLK_MASK;
-	switch (divisor) {
-	default:
-	case 1:
-		reg |= CURRENT_GATE_M2XCLK_DIV_1;
-		break;
-	case 2:
-		reg |= CURRENT_GATE_M2XCLK_DIV_2;
-		break;
-	case 3:
-		reg |= CURRENT_GATE_M2XCLK_DIV_3;
-		break;
-	case 4:
-		reg |= CURRENT_GATE_M2XCLK_DIV_4;
-		break;
-	}
+	if (divisor == 0 || divisor > 4)
+		divisor = 1;
+	reg |= CURRENT_GATE_M2XCLK_DIV(divisor);
 
 	sm750_set_current_gate(reg);
 }
diff --git a/drivers/staging/sm750fb/ddk750_reg.h b/drivers/staging/sm750fb/ddk750_reg.h
index fe412ead7..b796e32ab 100644
--- a/drivers/staging/sm750fb/ddk750_reg.h
+++ b/drivers/staging/sm750fb/ddk750_reg.h
@@ -312,10 +312,7 @@
     #define CURRENT_GATE_M2XCLK_112MHZ                (0x2 << 12)
     #define CURRENT_GATE_M2XCLK_84MHZ                 (0x3 << 12)
 #else
-    #define CURRENT_GATE_M2XCLK_DIV_1                 (0x0 << 12)
-    #define CURRENT_GATE_M2XCLK_DIV_2                 (0x1 << 12)
-    #define CURRENT_GATE_M2XCLK_DIV_3                 (0x2 << 12)
-    #define CURRENT_GATE_M2XCLK_DIV_4                 (0x3 << 12)
+    #define CURRENT_GATE_M2XCLK_DIV(divisor)          (((divisor) - 1) << 12)
 #endif
 #define CURRENT_GATE_VGA                              BIT(10)
 #define CURRENT_GATE_PWM                              BIT(9)
-- 
2.56.0

Re: [PATCH] staging: sm750fb: Simplify M2XCLK divisor encoding

[Greg KH]

On Sun, Oct 18, 2026 at 02:56:51PM +0530, himanshu bakshi wrote:
> Replace the switch statement with a macro to encode the M2XCLK
> divisor in the corresponding register bits.

Why?

> This is my first Linux kernel patch.

Great, but that doesn't need to be in the changelog :)

> Signed-off-by: himanshu bakshi <himanshu.bakshi478@gmail.com>

Capital letters please.

> ---
>  drivers/staging/sm750fb/ddk750_chip.c | 18 +++---------------
>  drivers/staging/sm750fb/ddk750_reg.h  |  5 +----
>  2 files changed, 4 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/staging/sm750fb/ddk750_chip.c b/drivers/staging/sm750fb/ddk750_chip.c
> index aa78d0bc1..2cb849dea 100644
> --- a/drivers/staging/sm750fb/ddk750_chip.c
> +++ b/drivers/staging/sm750fb/ddk750_chip.c
> @@ -109,21 +109,9 @@ static void set_memory_clock(unsigned int frequency)
>  
>  	/* Set the corresponding divisor in the register. */
>  	reg = peek32(CURRENT_GATE) & ~CURRENT_GATE_M2XCLK_MASK;
> -	switch (divisor) {
> -	default:
> -	case 1:
> -		reg |= CURRENT_GATE_M2XCLK_DIV_1;
> -		break;
> -	case 2:
> -		reg |= CURRENT_GATE_M2XCLK_DIV_2;
> -		break;
> -	case 3:
> -		reg |= CURRENT_GATE_M2XCLK_DIV_3;
> -		break;
> -	case 4:
> -		reg |= CURRENT_GATE_M2XCLK_DIV_4;
> -		break;
> -	}
> +	if (divisor == 0 || divisor > 4)
> +		divisor = 1;
> +	reg |= CURRENT_GATE_M2XCLK_DIV(divisor);
>  
>  	sm750_set_current_gate(reg);
>  }
> diff --git a/drivers/staging/sm750fb/ddk750_reg.h b/drivers/staging/sm750fb/ddk750_reg.h
> index fe412ead7..b796e32ab 100644
> --- a/drivers/staging/sm750fb/ddk750_reg.h
> +++ b/drivers/staging/sm750fb/ddk750_reg.h
> @@ -312,10 +312,7 @@
>      #define CURRENT_GATE_M2XCLK_112MHZ                (0x2 << 12)
>      #define CURRENT_GATE_M2XCLK_84MHZ                 (0x3 << 12)
>  #else
> -    #define CURRENT_GATE_M2XCLK_DIV_1                 (0x0 << 12)
> -    #define CURRENT_GATE_M2XCLK_DIV_2                 (0x1 << 12)
> -    #define CURRENT_GATE_M2XCLK_DIV_3                 (0x2 << 12)
> -    #define CURRENT_GATE_M2XCLK_DIV_4                 (0x3 << 12)
> +    #define CURRENT_GATE_M2XCLK_DIV(divisor)          (((divisor) - 1) << 12)

The original is more descriptive of the hardware data sheet, right?

thanks,

greg k-h