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

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Date:   Tue, 01 Sep 2020 10:11:38 -0400
From:   "Liam Beguin" <liambeguin@...il.com>
To:     "Vinod Koul" <vkoul@...nel.org>
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 Vinod,

On Mon Aug 31, 2020 at 7:08 AM EDT, Vinod Koul wrote:
> 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?
>

u8p_replace_bits seemed like a more concise notation.

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

I added the type casts to get rid of compilation warnings.

> >  
> >  	/* 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

Thanks,
Liam