linux-kernel - Re: [PATCH v1 1/1] phy: tusb1210: use bitmasks to set VENDOR

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Message-ID: <20200713050839.GS34333@vkoul-mobl>
Date:   Mon, 13 Jul 2020 10:38:39 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Liam Beguin <liambeguin@...il.com>
Cc:     kishon@...com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] phy: tusb1210: use bitmasks to set
 VENDOR_SPECIFIC2

On 01-07-20, 21:06, Liam Beguin wrote:
> From: Liam Beguin <lvb@...hos.com>
> 
> Start by reading the content of the VENDOR_SPECIFIC2 register and update
> each bit field based on device properties when defined.
> 
> The use of bit masks prevents fields from overriding each other and
> enables users to clear bits which are set by default, like datapolarity
> in this instance.
> 
> Signed-off-by: Liam Beguin <lvb@...hos.com>
> ---
>  drivers/phy/ti/phy-tusb1210.c | 29 ++++++++++++++++-------------
>  1 file changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/phy/ti/phy-tusb1210.c b/drivers/phy/ti/phy-tusb1210.c
> index d8d0cc11d187..a957655ebd36 100644
> --- a/drivers/phy/ti/phy-tusb1210.c
> +++ b/drivers/phy/ti/phy-tusb1210.c
> @@ -13,9 +13,9 @@
>  #include <linux/phy/ulpi_phy.h>
>  
>  #define TUSB1210_VENDOR_SPECIFIC2		0x80
> -#define TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT	0
> -#define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_SHIFT	4
> -#define TUSB1210_VENDOR_SPECIFIC2_DP_SHIFT	6
> +#define TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK	0x0f
> +#define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK	0x30

Why not be better and use GENMASK(3, 0) and GENMASK(5, 4) for these

> +#define TUSB1210_VENDOR_SPECIFIC2_DP_MASK	BIT(6)
>  
>  struct tusb1210 {
>  	struct ulpi *ulpi;
> @@ -118,22 +118,25 @@ static int tusb1210_probe(struct ulpi *ulpi)
>  	 * diagram optimization and DP/DM swap.
>  	 */
>  
> +	reg = ulpi_read(ulpi, TUSB1210_VENDOR_SPECIFIC2);
> +
>  	/* High speed output drive strength configuration */
> -	device_property_read_u8(&ulpi->dev, "ihstx", &val);
> -	reg = val << TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT;
> +	if (!device_property_read_u8(&ulpi->dev, "ihstx", &val))
> +		reg = (reg & ~TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK) |
> +			(val & TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK);

It would be better to use a helper to do this

>  
>  	/* High speed output impedance configuration */
> -	device_property_read_u8(&ulpi->dev, "zhsdrv", &val);
> -	reg |= val << TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_SHIFT;
> +	if (!device_property_read_u8(&ulpi->dev, "zhsdrv", &val))
> +		reg = (reg & ~TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK) |
> +			(val & TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK);
>  
>  	/* DP/DM swap control */
> -	device_property_read_u8(&ulpi->dev, "datapolarity", &val);
> -	reg |= val << TUSB1210_VENDOR_SPECIFIC2_DP_SHIFT;
> +	if (!device_property_read_u8(&ulpi->dev, "datapolarity", &val))
> +		reg = (reg & ~TUSB1210_VENDOR_SPECIFIC2_DP_MASK) |
> +			(val & TUSB1210_VENDOR_SPECIFIC2_DP_MASK);
>  
> -	if (reg) {
> -		ulpi_write(ulpi, TUSB1210_VENDOR_SPECIFIC2, reg);
> -		tusb->vendor_specific2 = reg;
> -	}
> +	ulpi_write(ulpi, TUSB1210_VENDOR_SPECIFIC2, reg);
> +	tusb->vendor_specific2 = reg;
>  
>  	tusb->phy = ulpi_phy_create(ulpi, &phy_ops);
>  	if (IS_ERR(tusb->phy))
> 
> base-commit: cd77006e01b3198c75fb7819b3d0ff89709539bb

fatal: bad object cd77006e01b3198c75fb7819b3d0ff89709539bb in
linux-phy.git

-- 
~Vinod