linux-kernel - Re: [PATCH 2/4] tmp/tpm_crb: fix Intel PTT hw bug during idle state

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Date:   Sat, 8 Oct 2016 15:50:03 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Tomas Winkler <tomas.winkler@...el.com>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] tmp/tpm_crb: fix Intel PTT hw bug during idle state

On Sat, Oct 08, 2016 at 02:59:37PM +0300, Tomas Winkler wrote:
> From: "Winkler, Tomas" <tomas.winkler@...el.com>
> 
> There is a HW bug in Skylake, Kabylake, and Broxton PCH Intel PTT device,
> where most of the registers in the control area except START, REQUEST,
> CANCEL, and LOC_CTRL lost retention when the device is in the idle state.
> Hence we need to bring the device to ready state before accessing the other
> registers. The fix brings device to ready state before trying to read
> command and response buffer addresses in order to remap the for access.
> 
> Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> ---
> V2: cmd read need to be called also before crb_init as this will run
>  self test.
> V3: resend.
> V4: add Kabylake to the list of effected platforms
> 
>  drivers/char/tpm/tpm_crb.c | 47 ++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 39 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> index 0f3b3f3d12d3..4eb96b85c653 100644
> --- a/drivers/char/tpm/tpm_crb.c
> +++ b/drivers/char/tpm/tpm_crb.c
> @@ -319,6 +319,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
>  	struct list_head resources;
>  	struct resource io_res;
>  	struct device *dev = &device->dev;
> +	u32 pa_high, pa_low;
>  	u64 cmd_pa;
>  	u32 cmd_size;
>  	u64 rsp_pa;
> @@ -346,12 +347,27 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
>  	if (IS_ERR(priv->cca))
>  		return PTR_ERR(priv->cca);
>  
> -	cmd_pa = ((u64) ioread32(&priv->cca->cmd_pa_high) << 32) |
> -		  (u64) ioread32(&priv->cca->cmd_pa_low);
> +	/*
> +	 * PTT HW bug w/a: wake up the device to access
> +	 * possibly not retained registers.
> +	 */
> +	ret = crb_cmd_ready(dev, priv);
> +	if (ret)
> +		return ret;
> +
> +	pa_high = ioread32(&priv->cca->cmd_pa_high);
> +	pa_low  = ioread32(&priv->cca->cmd_pa_low);
> +	cmd_pa = ((u64)pa_high << 32) | pa_low;
>  	cmd_size = ioread32(&priv->cca->cmd_size);
> +
> +	dev_dbg(dev, "cmd_hi = %X cmd_low = %X cmd_size %X\n",
> +		pa_high, pa_low, cmd_size);
> +
>  	priv->cmd = crb_map_res(dev, priv, &io_res, cmd_pa, cmd_size);
> -	if (IS_ERR(priv->cmd))
> -		return PTR_ERR(priv->cmd);
> +	if (IS_ERR(priv->cmd)) {
> +		ret = PTR_ERR(priv->cmd);
> +		goto out;
> +	}
>  
>  	memcpy_fromio(&rsp_pa, &priv->cca->rsp_pa, 8);
>  	rsp_pa = le64_to_cpu(rsp_pa);
> @@ -359,7 +375,8 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
>  
>  	if (cmd_pa != rsp_pa) {
>  		priv->rsp = crb_map_res(dev, priv, &io_res, rsp_pa, rsp_size);
> -		return PTR_ERR_OR_ZERO(priv->rsp);
> +		ret = PTR_ERR_OR_ZERO(priv->rsp);
> +		goto out;
>  	}
>  
>  	/* According to the PTP specification, overlapping command and response
> @@ -367,12 +384,18 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
>  	 */
>  	if (cmd_size != rsp_size) {
>  		dev_err(dev, FW_BUG "overlapping command and response buffer sizes are not identical");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
> +
>  	priv->cmd_size = cmd_size;
>  
>  	priv->rsp = priv->cmd;
> -	return 0;
> +
> +out:
> +	crb_go_idle(dev, priv);
> +
> +	return ret;
>  }
>  
>  static int crb_acpi_add(struct acpi_device *device)
> @@ -416,7 +439,15 @@ static int crb_acpi_add(struct acpi_device *device)
>  	if (rc)
>  		return rc;
>  
> -	return crb_init(device, priv);
> +	rc  = crb_cmd_ready(dev, priv);
> +	if (rc)
> +		return rc;

I cannot find any valid reason why crb_map_io calls crb_go_idle in the
except in the case of a failure. This is something I complained earlier.

A minor thing but the extra crb_cmd_ready is basically clutter to the
initialization.

/Jarkko