linux-kernel - RE: [tpmdd-devel] [PATCH 2/3] tpm_crb: encapsulate crb_wait_for_reg

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Message-ID: <5B8DA87D05A7694D9FA63FD143655C1B542F7FD8@hasmsx108.ger.corp.intel.com>
Date:   Tue, 11 Oct 2016 10:21:03 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>
CC:     "moderated list:TPM DEVICE DRIVER" 
        <tpmdd-devel@...ts.sourceforge.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [tpmdd-devel] [PATCH 2/3] tpm_crb: encapsulate
 crb_wait_for_reg_32

> Encapsulated crb_wait_for_reg32() so that state changes in other CRB registers
> than TPM_CRB_CTRL_REQ_x can be waited.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  drivers/char/tpm/tpm_crb.c | 40 +++++++++++++++++++++++-----------------
>  1 file changed, 23 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c index
> c34318b..45f53c2 100644
> --- a/drivers/char/tpm/tpm_crb.c
> +++ b/drivers/char/tpm/tpm_crb.c
> @@ -121,6 +121,25 @@ static int __maybe_unused crb_go_idle(struct device
> *dev, struct crb_priv *priv)
>  	return 0;
>  }
> 
> +static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
> +				unsigned long timeout)
This is a boiler plate register polling function  I would call it _poll_ rather the _wait_

> +{
> +	ktime_t start;
> +	ktime_t stop;
> +
> +	start = ktime_get();
> +	stop = ktime_add(start, ms_to_ktime(timeout));
> +
> +	do {
> +		if ((ioread32(reg) & mask) == value)
I prefer the register value is synced to  variable, this inlining is harder to add adhoc debug prints. 
Also you removed the debug print out that I know when this settled which is important for catching bugs. 
> +			return true;
> +
> +		usleep_range(50, 100);
How do you know this is correct sleep time, I've tuned that for power gating I'm not sure you this fits also for locality. 
> +	} while (ktime_before(ktime_get(), stop));
> +
> +	return false;
> +}
> +

>  /**
>   * crb_cmd_ready - request tpm crb device to enter ready state
>   *
> @@ -138,27 +157,14 @@ static int __maybe_unused crb_go_idle(struct device
> *dev, struct crb_priv *priv)  static int __maybe_unused crb_cmd_ready(struct
> device *dev,
>  					struct crb_priv *priv)
>  {
> -	ktime_t stop, start;
> -	u32 req;
> -
>  	if (priv->flags & CRB_FL_ACPI_START)
>  		return 0;
> 
>  	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);
> -
> -	start = ktime_get();
> -	stop = ktime_add(start, ms_to_ktime(TPM2_TIMEOUT_C));
> -	do {
> -		req = ioread32(&priv->regs_t->ctrl_req);
> -		if (!(req & CRB_CTRL_REQ_CMD_READY)) {
> -			dev_dbg(dev, "cmdReady in %lld usecs\n",
> -				ktime_to_us(ktime_sub(ktime_get(), start)));
> -			return 0;
> -		}
> -		usleep_range(50, 100);
> -	} while (ktime_before(ktime_get(), stop));
> -
> -	if (ioread32(&priv->regs_t->ctrl_req) & CRB_CTRL_REQ_CMD_READY) {
> +	if (!crb_wait_for_reg_32(&priv->regs_t->ctrl_req,
> +				 CRB_CTRL_REQ_CMD_READY /* mask */,
> +				 0, /* value */
> +				 TPM2_TIMEOUT_C)) {
>  		dev_warn(dev, "cmdReady timed out\n");
>  		return -ETIME;
>  	}
> --
> 2.7.4
> 
> 
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