Re: [PATCH v1] clk: nuvoton: add read only feature for clk driver

[Sean Anderson <seanga2@gmail.com>]

On 3/7/23 03:13, Jim Liu wrote:
> Set ahb/apb/fiu clock divider as read-only

Are these read-only in hardware, or is there some other reason?

--Sean

> Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
> ---
>   drivers/clk/nuvoton/clk_npcm.c    | 15 ++++++++++++---
>   drivers/clk/nuvoton/clk_npcm.h    |  1 +
>   drivers/clk/nuvoton/clk_npcm8xx.c | 12 ++++++------
>   3 files changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/clk/nuvoton/clk_npcm.c b/drivers/clk/nuvoton/clk_npcm.c
> index 8d71f2a24b..18cb9cddbf 100644
> --- a/drivers/clk/nuvoton/clk_npcm.c
> +++ b/drivers/clk/nuvoton/clk_npcm.c
> @@ -135,7 +135,7 @@ static u32 npcm_clk_get_div(struct clk *clk)
>   	return div;
>   }
>   
> -static u32 npcm_clk_set_div(struct clk *clk, u32 div)
> +static int npcm_clk_set_div(struct clk *clk, u32 div)
>   {
>   	struct npcm_clk_priv *priv = dev_get_priv(clk->dev);
>   	struct npcm_clk_div *divider;
> @@ -145,6 +145,9 @@ static u32 npcm_clk_set_div(struct clk *clk, u32 div)
>   	if (!divider)
>   		return -EINVAL;
>   
> +	if (divider->flags & DIV_RO)
> +		return 0;
> +
>   	if (divider->flags & PRE_DIV2)
>   		div = div >> 1;
>   
> @@ -153,6 +156,12 @@ static u32 npcm_clk_set_div(struct clk *clk, u32 div)
>   	else
>   		clkdiv = ilog2(div);
>   
> +	if (clkdiv > (divider->mask >> (ffs(divider->mask) - 1))) {
> +		printf("clkdiv(%d) for clk(%ld) is over limit\n",
> +		       clkdiv, clk->id);
> +		return -EINVAL;
> +	}
> +
>   	val = readl(priv->base + divider->reg);
>   	val &= ~divider->mask;
>   	val |= (clkdiv << (ffs(divider->mask) - 1)) & divider->mask;
> @@ -253,8 +262,8 @@ static ulong npcm_clk_set_rate(struct clk *clk, ulong rate)
>   	if (ret)
>   		return ret;
>   
> -	debug("%s: rate %lu, new rate (%lu / %u)\n", __func__, rate, parent_rate, div);
> -	return (parent_rate / div);
> +	debug("%s: rate %lu, new rate %lu\n", __func__, rate, npcm_clk_get_rate(clk));
> +	return npcm_clk_get_rate(clk);
>   }
>   
>   static int npcm_clk_set_parent(struct clk *clk, struct clk *parent)
> diff --git a/drivers/clk/nuvoton/clk_npcm.h b/drivers/clk/nuvoton/clk_npcm.h
> index 06b60dc8b8..b4726d8381 100644
> --- a/drivers/clk/nuvoton/clk_npcm.h
> +++ b/drivers/clk/nuvoton/clk_npcm.h
> @@ -50,6 +50,7 @@
>   #define PRE_DIV2	BIT(2)	/* Pre divisor = 2 */
>   #define POST_DIV2	BIT(3)	/* Post divisor = 2 */
>   #define FIXED_PARENT	BIT(4)	/* clock source is fixed */
> +#define DIV_RO		BIT(5)	/* divider is read-only */
>   
>   /* Parameters of PLL configuration */
>   struct npcm_clk_pll {
> diff --git a/drivers/clk/nuvoton/clk_npcm8xx.c b/drivers/clk/nuvoton/clk_npcm8xx.c
> index 27e3cfcf55..d1b32e3237 100644
> --- a/drivers/clk/nuvoton/clk_npcm8xx.c
> +++ b/drivers/clk/nuvoton/clk_npcm8xx.c
> @@ -45,12 +45,12 @@ static struct npcm_clk_select npcm8xx_clk_selectors[] = {
>   };
>   
>   static struct npcm_clk_div npcm8xx_clk_dividers[] = {
> -	{NPCM8XX_CLK_AHB, CLKDIV1, CLK4DIV, DIV_TYPE1 | PRE_DIV2},
> -	{NPCM8XX_CLK_APB2, CLKDIV2, APB2CKDIV, DIV_TYPE2},
> -	{NPCM8XX_CLK_APB5, CLKDIV2, APB5CKDIV, DIV_TYPE2},
> -	{NPCM8XX_CLK_SPI0, CLKDIV3, SPI0CKDIV, DIV_TYPE1},
> -	{NPCM8XX_CLK_SPI1, CLKDIV3, SPI1CKDIV, DIV_TYPE1},
> -	{NPCM8XX_CLK_SPI3, CLKDIV1, SPI3CKDIV, DIV_TYPE1},
> +	{NPCM8XX_CLK_AHB, CLKDIV1, CLK4DIV, DIV_TYPE1 | PRE_DIV2 | DIV_RO},
> +	{NPCM8XX_CLK_APB2, CLKDIV2, APB2CKDIV, DIV_TYPE2 | DIV_RO},
> +	{NPCM8XX_CLK_APB5, CLKDIV2, APB5CKDIV, DIV_TYPE2 | DIV_RO},
> +	{NPCM8XX_CLK_SPI0, CLKDIV3, SPI0CKDIV, DIV_TYPE1 | DIV_RO},
> +	{NPCM8XX_CLK_SPI1, CLKDIV3, SPI1CKDIV, DIV_TYPE1 | DIV_RO},
> +	{NPCM8XX_CLK_SPI3, CLKDIV1, SPI3CKDIV, DIV_TYPE1 | DIV_RO},
>   	{NPCM8XX_CLK_SPIX, CLKDIV3, SPIXCKDIV, DIV_TYPE1},
>   	{NPCM8XX_CLK_UART, CLKDIV1, UARTDIV1, DIV_TYPE1},
>   	{NPCM8XX_CLK_UART2, CLKDIV3, UARTDIV2, DIV_TYPE1},