linux-kernel - Re: [PATCH v4 1/1] phy: tusb1210: use bitmasks to set VENDOR

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Date:   Mon, 31 Aug 2020 16:38:52 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Liam Beguin <liambeguin@...il.com>
Cc:     geert@...ux-m68k.org, kishon@...com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/1] phy: tusb1210: use bitmasks to set
 VENDOR_SPECIFIC2

Hi Liam,

On 22-08-20, 16:53, 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>
> ---
> Changes since v1:
> - use set_mask_bits
> 
> Changes since v2:
> - fix missing bit shift dropped in v2
> - rebase on 5.9-rc1
> 
> Changes since v3:
> - switch to u8p_replace_bits() since there's little reason to protect
>   against concurrent access
> 
>  drivers/phy/ti/phy-tusb1210.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/phy/ti/phy-tusb1210.c b/drivers/phy/ti/phy-tusb1210.c
> index d8d0cc11d187..a63213f5972a 100644
> --- a/drivers/phy/ti/phy-tusb1210.c
> +++ b/drivers/phy/ti/phy-tusb1210.c
> @@ -7,15 +7,16 @@
>   * Author: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
>   */
>  #include <linux/module.h>
> +#include <linux/bitfield.h>
>  #include <linux/ulpi/driver.h>
>  #include <linux/ulpi/regs.h>
>  #include <linux/gpio/consumer.h>
>  #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	GENMASK(3, 0)
> +#define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK	GENMASK(5, 4)
> +#define TUSB1210_VENDOR_SPECIFIC2_DP_MASK	BIT(6)
>  
>  struct tusb1210 {
>  	struct ulpi *ulpi;
> @@ -118,22 +119,22 @@ 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))
> +		u8p_replace_bits(&reg, val, (u8)TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK);

Any reason for using u8p_replace_bits and not u8_replace_bits? 

Also please drop the u8 casts above, they seem unnecessary here

>  
>  	/* 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))
> +		u8p_replace_bits(&reg, val, (u8)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))
> +		u8p_replace_bits(&reg, val, (u8)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: 9123e3a74ec7b934a4a099e98af6a61c2f80bbf5
> -- 
> 2.27.0

-- 
~Vinod