netdev - Re: [PATCH v2 1/4] net: macb: Check MDIO state before read/write and use timeouts

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Date:   Mon, 26 Nov 2018 14:46:01 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <harini.katakam@...inx.com>, <Nicolas.Ferre@...rochip.com>,
        <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <michal.simek@...inx.com>, <harinikatakamlinux@...il.com>,
        <harinik@...inx.com>, <shubhrajyoti.datta@...inx.com>,
        <sai.pavan.boddu@...inx.com>
Subject: Re: [PATCH v2 1/4] net: macb: Check MDIO state before read/write and
 use timeouts

Hi Harini,

On 26.11.2018 09:07, Harini Katakam wrote:
> From: Harini Katakam <harinik@...inx.com>
> 
> Replace the while loop in MDIO read/write functions with a timeout.
> In addition, add a check for MDIO bus busy before initiating a new
> operation as well to make sure there is no ongoing MDIO operation.

Is this MDIO bus busy check necessary? The caller of
macb_mdio_read/macb_mdio_write locks the mdio bus mutex before calling it
(e.g. mdiobus_read).

> 
> Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
> Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@...inx.com>
> Signed-off-by: Harini Katakam <harinik@...inx.com>
> ---
> v2 changes:
> Use readx_poll_timeout
> 
> Changes form RFC:
> Cleaned up timeout implementation and moved it to a helper.
> 
>  drivers/net/ethernet/cadence/macb.h      |  3 +++
>  drivers/net/ethernet/cadence/macb_main.c | 33 ++++++++++++++++++++++++++------
>  2 files changed, 30 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> index 3d45f4c..df7bee1 100644
> --- a/drivers/net/ethernet/cadence/macb.h
> +++ b/drivers/net/ethernet/cadence/macb.h
> @@ -714,6 +714,9 @@
>  		__v; \
>  	})
>  
> +#define MACB_IDLE_MASK		(1 << MACB_IDLE_OFFSET)

You could use MACB_BIT(IDLE) instead.

> +#define MACB_READ_NSR(bp)	macb_readl(bp, NSR)

Is this necessary?


> +
>  /* struct macb_dma_desc - Hardware DMA descriptor
>   * @addr: DMA address of data buffer
>   * @ctrl: Control and status bits
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 1d86b4d..fd86ece 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -36,6 +36,7 @@
>  #include <linux/ip.h>
>  #include <linux/udp.h>
>  #include <linux/tcp.h>
> +#include <linux/iopoll.h>
>  #include "macb.h"
>  
>  #define MACB_RX_BUFFER_SIZE	128
> @@ -79,6 +80,8 @@
>   */
>  #define MACB_HALT_TIMEOUT	1230
>  
> +#define MACB_MDIO_TIMEOUT	1000000 /* in usecs */
> +
>  /* DMA buffer descriptor might be different size
>   * depends on hardware configuration:
>   *
> @@ -318,10 +321,23 @@ static void macb_get_hwaddr(struct macb *bp)
>  	eth_hw_addr_random(bp->dev);
>  }
>  
> +static int macb_mdio_wait_for_idle(struct macb *bp)
> +{
> +	u32 val;
> +
> +	return readx_poll_timeout(MACB_READ_NSR, bp, val, val & MACB_IDLE_MASK,
> +				  1, MACB_MDIO_TIMEOUT);
> +}
> +
>  static int macb_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
>  {
>  	struct macb *bp = bus->priv;
>  	int value;
> +	int err;
> +
> +	err = macb_mdio_wait_for_idle(bp);
> +	if (err < 0)
> +		return err;
>  
>  	macb_writel(bp, MAN, (MACB_BF(SOF, MACB_MAN_SOF)
>  			      | MACB_BF(RW, MACB_MAN_READ)
> @@ -329,9 +345,9 @@ static int macb_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
>  			      | MACB_BF(REGA, regnum)
>  			      | MACB_BF(CODE, MACB_MAN_CODE)));
>  
> -	/* wait for end of transfer */
> -	while (!MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
> -		cpu_relax();
> +	err = macb_mdio_wait_for_idle(bp);
> +	if (err < 0)
> +		return err;
>  
>  	value = MACB_BFEXT(DATA, macb_readl(bp, MAN));
>  
> @@ -342,6 +358,11 @@ static int macb_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
>  			   u16 value)
>  {
>  	struct macb *bp = bus->priv;
> +	int err;
> +
> +	err = macb_mdio_wait_for_idle(bp);
> +	if (err < 0)
> +		return err;
>  
>  	macb_writel(bp, MAN, (MACB_BF(SOF, MACB_MAN_SOF)
>  			      | MACB_BF(RW, MACB_MAN_WRITE)
> @@ -350,9 +371,9 @@ static int macb_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
>  			      | MACB_BF(CODE, MACB_MAN_CODE)
>  			      | MACB_BF(DATA, value)));
>  
> -	/* wait for end of transfer */
> -	while (!MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
> -		cpu_relax();
> +	err = macb_mdio_wait_for_idle(bp);
> +	if (err < 0)
> +		return err;
>  
>  	return 0;
>  }
>