linux-kernel - RE: [PATCH v3] tpm: Enable CLKRUN protocol for Braswell systems

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Date:   Thu, 8 Jun 2017 01:11:43 +0000
From:   "Shaikh, Azhar" <azhar.shaikh@...el.com>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
CC:     "jarkko.sakkinen@...ux.intel.com" <jarkko.sakkinen@...ux.intel.com>,
        "jgunthorpe@...idianresearch.com" <jgunthorpe@...idianresearch.com>,
        "tpmdd-devel@...ts.sourceforge.net" 
        <tpmdd-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Subject: RE: [PATCH v3] tpm: Enable CLKRUN protocol for Braswell systems



> -----Original Message-----
> From: Alan Cox [mailto:gnomes@...rguk.ukuu.org.uk]
> Sent: Wednesday, June 7, 2017 2:45 PM
> To: Shaikh, Azhar <azhar.shaikh@...el.com>
> Cc: jarkko.sakkinen@...ux.intel.com; jgunthorpe@...idianresearch.com;
> tpmdd-devel@...ts.sourceforge.net; linux-kernel@...r.kernel.org; linux-
> security-module@...r.kernel.org
> Subject: Re: [PATCH v3] tpm: Enable CLKRUN protocol for Braswell systems
> 
> > +++ b/drivers/char/tpm/tpm_tis.c
> > @@ -89,13 +89,89 @@ static inline int is_itpm(struct acpi_device *dev)
> > }  #endif
> >
> > +#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
> 
> This isn't the only bit that is x86 specific
> 
> > +
> > +#define INTEL_LEGACY_BLK_BASE_ADDR      0xFED08000
> > +#define ILB_REMAP_SIZE			0x100
> > +#define LPC_CNTRL_REG_OFFSET            0x84
> > +#define LPC_CLKRUN_EN                   (1 << 2)
> > +
> > +void __iomem *ilb_base_addr;
> > +
> > +/**
> > + * 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;
> > +
> > +	if (!is_bsw())
> > +		return;
> > +
> > +	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);
> > +
> > +	/*
> > +	 * 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);
> > +
> > +	/* Make sure the above write is completed */
> > +	wmb();
> 
> Why the wmb(). It doesn't do what the comment says! Also this code is x86
> specific
> 
> 

Memory barrier to enforce the order so that the outb() is completed, which ensures that the LPC clocks are running before sending any TPM command.

> > +}
> > +
> > +/**
> > + * 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;
> > +
> > +	if (!is_bsw())
> > +		return;
> > +
> > +	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);
> > +
> > +	/*
> > +	 * 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);
> > +
> > +	/* Make sure the above write is completed */
> > +	wmb();
> > +}
> 
> Same
> 
> > +
> >  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);
> >
> > +	disable_lpc_clk_run();
> > +
> >  	while (len--)
> >  		*result++ = ioread8(phy->iobase + addr);
> > +
> > +	enable_lpc_clk_run();
> > +
> >  	return 0;
> >  }
> 
> So what you actually want to do is fold all the errata crap into an x86 specific
> chunk and just define disable/enable_lpc_clk_run() as null functions on
> everything else.
> 

Ok, will do.

> I'd pick better names too - if other platforms need a hook here it won't I
> imagine be about LPC. Possibly you want names like
> 
> 	platform_begin_tpm_xfer(data);
> 	platform_end_tpm_xfer(data);
> 

How about these? Since most of the functions in this driver begin with 'tpm_'
disable_lpc_clk_run()	- >	tpm_start_xfer()
enable_lpc_clk_run()	->	tpm_end_xfer()

> >
> > @@ -104,8 +180,13 @@ 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);
> >
> > +	disable_lpc_clk_run();
> > +
> >  	while (len--)
> >  		iowrite8(*value++, phy->iobase + addr);
> > +
> > +	enable_lpc_clk_run();
> > +
> >  	return 0;
> >  }
> >
> > @@ -113,7 +194,12 @@ 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);
> >
> > +	disable_lpc_clk_run();
> > +
> >  	*result = ioread16(phy->iobase + addr);
> > +
> > +	enable_lpc_clk_run();
> > +
> >  	return 0;
> >  }
> >
> > @@ -121,7 +207,12 @@ 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);
> >
> > +	disable_lpc_clk_run();
> > +
> >  	*result = ioread32(phy->iobase + addr);
> > +
> > +	enable_lpc_clk_run();
> > +
> >  	return 0;
> >  }
> >
> > @@ -129,7 +220,12 @@ 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);
> >
> > +	disable_lpc_clk_run();
> > +
> >  	iowrite32(value, phy->iobase + addr);
> > +
> > +	enable_lpc_clk_run();
> > +
> >  	return 0;
> >  }
> >
> > @@ -191,6 +287,10 @@ static int tpm_tis_pnp_init(struct pnp_dev
> *pnp_dev,
> >  		acpi_dev_handle = ACPI_HANDLE(&pnp_dev->dev);
> >  	}
> >
> > +	if (is_bsw())
> > +		ilb_base_addr = ioremap(INTEL_LEGACY_BLK_BASE_ADDR,
> > +					ILB_REMAP_SIZE);
> > +
> 
> This suggests to me that the bsw stuff wants to wrap the standard methods
> because it's weird and ugly having random magic hardware globals in what
> should be standard code.
> 
> >  	return tpm_tis_init(&pnp_dev->dev, &tpm_info, acpi_dev_handle);
> }
> >
> > @@ -214,6 +314,9 @@ static void tpm_tis_pnp_remove(struct pnp_dev
> > *dev)
> >
> >  	tpm_chip_unregister(chip);
> >  	tpm_tis_remove(chip);
> > +
> > +	if (is_bsw())
> > +		iounmap(ilb_base_addr);
> >  }
> >
> >  static struct pnp_driver tis_pnp_driver = {