linux-kernel - Re: [PATCH v6 4/4] tpm: tpm_tis

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Date:   Fri, 30 Aug 2019 08:40:42 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Heiko Stuebner <heiko@...ech.de>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Andrey Pronin <apronin@...omium.org>,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        Duncan Laurie <dlaurie@...omium.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Alexander Steffen <Alexander.Steffen@...ineon.com>,
        <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v6 4/4] tpm: tpm_tis_spi: Support cr50 devices

Quoting Heiko Stuebner (2019-08-30 08:33:48)
> Am Freitag, 30. August 2019, 00:41:10 CEST schrieb Stephen Boyd:
> > From: Andrey Pronin <apronin@...omium.org>
> > 
> > Add TPM2.0 PTP FIFO compatible SPI interface for chips with Cr50
> > firmware. The firmware running on the currently supported H1 Secure
> > Microcontroller requires a special driver to handle its specifics:
> > 
> >  - need to ensure a certain delay between SPI transactions, or else
> >    the chip may miss some part of the next transaction
> >  - if there is no SPI activity for some time, it may go to sleep,
> >    and needs to be waken up before sending further commands
> >  - access to vendor-specific registers
> > 
> > Cr50 firmware has a requirement to wait for the TPM to wakeup before
> > sending commands over the SPI bus. Otherwise, the firmware could be in
> > deep sleep and not respond. The method to wait for the device to wakeup
> > is slightly different than the usual flow control mechanism described in
> > the TCG SPI spec. Add a completion to tpm_tis_spi_transfer() before we
> > start a SPI transfer so we can keep track of the last time the TPM
> > driver accessed the SPI bus to support the flow control mechanism.
> > 
> > Split the cr50 logic off into a different file to keep it out of the
> > normal code flow of the existing SPI driver while making it all part of
> > the same module when the code is optionally compiled into the same
> > module. Export a new function, tpm_tis_spi_init(), and the associated
> > read/write/transfer APIs so that we can do this. Make the cr50 code wrap
> > the tpm_tis_spi_phy struct with its own struct to override the behavior
> > of tpm_tis_spi_transfer() by supplying a custom flow control hook. This
> > shares the most code between the core driver and the cr50 support
> > without combining everything into the core driver or exporting module
> > symbols.
> > 
> > Signed-off-by: Andrey Pronin <apronin@...omium.org>
> > Cc: Andrey Pronin <apronin@...omium.org>
> > Cc: Duncan Laurie <dlaurie@...omium.org>
> > Cc: Jason Gunthorpe <jgg@...pe.ca>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Guenter Roeck <groeck@...omium.org>
> > Cc: Alexander Steffen <Alexander.Steffen@...ineon.com>
> > Cc: Heiko Stuebner <heiko@...ech.de>
> > [swboyd@...omium.org: Replace boilerplate with SPDX tag, drop
> > suspended bit and remove ifdef checks in cr50.h, migrate to functions
> > exported in tpm_tis_spi.h, combine into one module instead of two]
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> 
> This variant breaks building the tpm as a module:
> 
> 
> WARNING: modpost: missing MODULE_LICENSE() in drivers/char/tpm/cr50_spi.o
> see include/linux/module.h for more information
> ERROR: "tpm_tis_spi_write32" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_read32" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_read16" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_init" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_transfer" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_resume" [drivers/char/tpm/tpm_tis_spi.ko] undefined!
> ERROR: "cr50_spi_probe" [drivers/char/tpm/tpm_tis_spi.ko] undefined!
> make[2]: *** [../scripts/Makefile.modpost:103: modules-modpost] Fehler 1
> make[1]: *** [/home/devel/hstuebner/00_git-repos/linux-rockchip/Makefile:1302: modules] Fehler 2
> make[1]: Verzeichnis „/home/devel/hstuebner/00_git-repos/linux-rockchip/_build-arm64“ wird verlassen
> make: *** [Makefile:179: sub-make] Fehler 2
> 
> 
> After adding a dummy MODULE_LICENSE I end up with:
> 
> ERROR: "tpm_tis_spi_write32" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_read32" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_read16" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_init" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_transfer" [drivers/char/tpm/cr50_spi.ko] undefined!
> ERROR: "tpm_tis_spi_resume" [drivers/char/tpm/tpm_tis_spi.ko] undefined!
> ERROR: "cr50_spi_probe" [drivers/char/tpm/tpm_tis_spi.ko] undefined!
> 
> 
> So building things as modules this way clearly is not working. Going back
> to the previous approach makes the module happy again, aka:
> 
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 6ff135d6f008..477fcddbff8c 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -21,7 +21,9 @@ tpm-$(CONFIG_EFI) += eventlog/efi.o
>  tpm-$(CONFIG_OF) += eventlog/of.o
>  obj-$(CONFIG_TCG_TIS_CORE) += tpm_tis_core.o
>  obj-$(CONFIG_TCG_TIS) += tpm_tis.o
> -obj-$(CONFIG_TCG_TIS_SPI) += tpm_tis_spi.o cr50_spi.o
> +obj-$(CONFIG_TCG_TIS_SPI) += tpm_tis_spi_mod.o
> +tpm_tis_spi_mod-y := tpm_tis_spi.o
> +tpm_tis_spi_mod-y += cr50_spi.o
>  obj-$(CONFIG_TCG_TIS_I2C_ATMEL) += tpm_i2c_atmel.o
>  obj-$(CONFIG_TCG_TIS_I2C_INFINEON) += tpm_i2c_infineon.o
>  obj-$(CONFIG_TCG_TIS_I2C_NUVOTON) += tpm_i2c_nuvoton.o
> 

I wasn't happy that I had to make a tpm_tis_spi_mod target to get the
.ko to build properly but I thought it was because of the extra Kconfig
option. If two files can't be combined into one .ko and have it be named
tpm_tis_spi.ko then we have to do the above workaround. Or we can
#include the cr50_spi.c file into tpm_tis_spi.c file. Or we can rename
tpm_tis_spi.c to tpm_tis_spi_base.c and then do the above change with a
tpm_tis_spi-y. Maybe Masahiro has some hints.