Re: [PATCH v2] tpm: Enable CLKRUN protocol for Braswell systems

[Jarkko Sakkinen]

On Thu, Jun 01, 2017 at 07:04:04PM -0700, Azhar Shaikh wrote:
> To overcome a hardware limitation on Intel Braswell systems,
> disable CLKRUN protocol during TPM transactions and re-enable
> once the transaction is completed.
> 
> Signed-off-by: Azhar Shaikh <azhar.shaikh@xxxxxxxxx>
> ---
> Changes from v1:
> - Add CONFIG_X86 around disable_lpc_clk_run () and enable_lpc_clk_run() to avoid
> - build breakage on architectures which do not implement kmap_atomic_pfn()
> 
>  drivers/char/tpm/tpm.h     | 20 ++++++++++
>  drivers/char/tpm/tpm_tis.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 114 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 4b4c8dee3096..98032a22317e 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -36,6 +36,10 @@
>  #include <linux/highmem.h>
>  #include <crypto/hash_info.h>
>  
> +#ifdef CONFIG_X86
> +#include <asm/intel-family.h>
> +#endif

#ifdef's are not necessary here.

> +
>  enum tpm_const {
>  	TPM_MINOR = 224,	/* officially assigned */
>  	TPM_BUFSIZE = 4096,
> @@ -436,6 +440,22 @@ struct tpm_buf {
>  	u8 *data;
>  };
>  
> +#define INTEL_LEGACY_BLK_BASE_ADDR	0xFED08000
> +#define LPC_CNTRL_REG_OFFSET		0x84
> +#define LPC_CLKRUN_EN			(1 << 2)
> +
> +#ifdef CONFIG_X86
> +static inline bool is_bsw(void)
> +{
> +	return ((boot_cpu_data.x86_model == INTEL_FAM6_ATOM_AIRMONT) ? 1 : 0);
> +}
> +#else
> +static inline bool is_bsw(void)
> +{
> +	return false;
> +}
> +#endif

Move these to tpm_tis.c right before disable_lpc_clk_run().

> +
>  static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
>  {
>  	struct tpm_input_header *head;
> diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
> index c7e1384f1b08..0c1496340a18 100644
> --- a/drivers/char/tpm/tpm_tis.c
> +++ b/drivers/char/tpm/tpm_tis.c
> @@ -89,13 +89,79 @@ static inline int is_itpm(struct acpi_device *dev)
>  }
>  #endif
>  
> +#ifdef CONFIG_X86
> +/**
> + * disable_lpc_clk_run() - clear LPC CLKRUN_EN i.e. clocks will be free running
> + */
> +static void disable_lpc_clk_run(void)
> +{
> +	u32 clkrun_val;
> +	void __iomem *ilb_base_addr = NULL;
> +
> +	ilb_base_addr = (void __iomem *)
> +		kmap_atomic_pfn(INTEL_LEGACY_BLK_BASE_ADDR >> PAGE_SHIFT);
> +
> +	clkrun_val = ioread32(ilb_base_addr + LPC_CNTRL_REG_OFFSET);
> +
> +	/* Disable LPC CLKRUN# */
> +	clkrun_val &= ~LPC_CLKRUN_EN;
> +	iowrite32(clkrun_val, ilb_base_addr + LPC_CNTRL_REG_OFFSET);
> +
> +	kunmap_atomic(ilb_base_addr);
> +	/*
> +	 * Write any random value on port 0x80 which is on LPC, to make
> +	 * sure LPC clock is running before sending any TPM command.
> +	 */
> +	outb(0x80, 0xCC);
> +}

You said that this code does not work compared to a version that does
only static ioremap.

I compared this to the other version. One of the major differences is
that outb() is done before releasing the mapping. Don't know or
understand what difference that would make but it is a semantic
difference.

Another observation is that should you have wmb() before outb() to make
sure that all the write operations are complete?

> +
> +/**
> + * enable_lpc_clk_run() - set LPC CLKRUN_EN i.e. clocks can be turned off
> + */
> +static void enable_lpc_clk_run(void)
> +{
> +	u32 clkrun_val;
> +	void __iomem *ilb_base_addr = NULL;
> +
> +	ilb_base_addr = (void __iomem *)
> +		kmap_atomic_pfn(INTEL_LEGACY_BLK_BASE_ADDR >> PAGE_SHIFT);
> +
> +	clkrun_val = ioread32(ilb_base_addr + LPC_CNTRL_REG_OFFSET);
> +
> +	/* Enable LPC CLKRUN# */
> +	clkrun_val |= LPC_CLKRUN_EN;
> +	iowrite32(clkrun_val, ilb_base_addr + LPC_CNTRL_REG_OFFSET);
> +
> +	kunmap_atomic(ilb_base_addr);
> +	/*
> +	 * Write any random value on port 0x80 which is on LPC, to make
> +	 * sure LPC clock is running before sending any TPM command.
> +	 */
> +	outb(0x80, 0xCC);
> +}
> +#else
> +static void disable_lpc_clk_run(void)
> +{
> +}
> +static void enable_lpc_clk_run(void)
> +{
> +}
> +#endif
> +
>  static int tpm_tcg_read_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
>  			      u8 *result)
>  {
>  	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
>  
> +	if (is_bsw())
> +		disable_lpc_clk_run();

Do is_bsw() instead inside so that this can be unconditionally called.

> +
>  	while (len--)
>  		*result++ = ioread8(phy->iobase + addr);
> +
> +	if (is_bsw())
> +		enable_lpc_clk_run();
> +
>  	return 0;
>  }
>  
> @@ -104,8 +170,15 @@ static int tpm_tcg_write_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
>  {
>  	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
>  
> +	if (is_bsw())
> +		disable_lpc_clk_run();
> +
>  	while (len--)
>  		iowrite8(*value++, phy->iobase + addr);
> +
> +	if (is_bsw())
> +		enable_lpc_clk_run();
> +
>  	return 0;
>  }
>  
> @@ -113,7 +186,14 @@ static int tpm_tcg_read16(struct tpm_tis_data *data, u32 addr, u16 *result)
>  {
>  	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
>  
> +	if (is_bsw())
> +		disable_lpc_clk_run();
> +
>  	*result = ioread16(phy->iobase + addr);
> +
> +	if (is_bsw())
> +		enable_lpc_clk_run();
> +
>  	return 0;
>  }
>  
> @@ -121,7 +201,14 @@ static int tpm_tcg_read32(struct tpm_tis_data *data, u32 addr, u32 *result)
>  {
>  	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
>  
> +	if (is_bsw())
> +		disable_lpc_clk_run();
> +
>  	*result = ioread32(phy->iobase + addr);
> +
> +	if (is_bsw())
> +		enable_lpc_clk_run();
> +
>  	return 0;
>  }
>  
> @@ -129,7 +216,14 @@ static int tpm_tcg_write32(struct tpm_tis_data *data, u32 addr, u32 value)
>  {
>  	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
>  
> +	if (is_bsw())
> +		disable_lpc_clk_run();
> +
>  	iowrite32(value, phy->iobase + addr);
> +
> +	if (is_bsw())
> +		enable_lpc_clk_run();
> +
>  	return 0;
>  }
>  
> -- 
> 1.9.1
> 

/Jarkko