Re: [PATCH v7 02/12] firmware: qcom: scm: enable the TZ mem allocator

Bartosz Golaszewski
2024-02-21T18:39:31Z

On Sun, Feb 18, 2024 at 4:25 AM Bjorn Andersson <andersson@kernel.org> wrote:
>
> On Mon, Feb 05, 2024 at 07:28:00PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > Select the TrustZone memory allocator in Kconfig and create a pool of
> > memory shareable with the TrustZone when probing the SCM driver.
> >
> > This will allow a gradual conversion of all relevant SCM calls to using
> > the dedicated allocator.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
> > Tested-by: Andrew Halaney <ahalaney@redhat.com> # sc8280xp-lenovo-thinkpad-x13s
> > Tested-by: Deepti Jaggi <quic_djaggi@quicinc.com> #sa8775p-ride
> > Reviewed-by: Elliot Berman <quic_eberman@quicinc.com>
> > ---
> > drivers/firmware/qcom/Kconfig | 1 +
> > drivers/firmware/qcom/qcom_scm.c | 16 ++++++++++++++++
> > 2 files changed, 17 insertions(+)
> >
> > diff --git a/drivers/firmware/qcom/Kconfig b/drivers/firmware/qcom/Kconfig
> > index f18686edf415..d24d83223867 100644
> > --- a/drivers/firmware/qcom/Kconfig
> > +++ b/drivers/firmware/qcom/Kconfig
> > @@ -7,6 +7,7 @@
> > menu "Qualcomm firmware drivers"
> >
> > config QCOM_SCM
> > + select QCOM_TZMEM
> > tristate
> >
> > config QCOM_TZMEM
> > diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
> > index 520de9b5633a..0d4c028be0c1 100644
> > --- a/drivers/firmware/qcom/qcom_scm.c
> > +++ b/drivers/firmware/qcom/qcom_scm.c
> > @@ -8,8 +8,10 @@
> > #include <linux/completion.h>
> > #include <linux/cpumask.h>
> > #include <linux/dma-mapping.h>
> > +#include <linux/err.h>
> > #include <linux/export.h>
> > #include <linux/firmware/qcom/qcom_scm.h>
> > +#include <linux/firmware/qcom/qcom_tzmem.h>
> > #include <linux/init.h>
> > #include <linux/interconnect.h>
> > #include <linux/interrupt.h>
> > @@ -20,9 +22,11 @@
> > #include <linux/of_platform.h>
> > #include <linux/platform_device.h>
> > #include <linux/reset-controller.h>
> > +#include <linux/sizes.h>
> > #include <linux/types.h>
> >
> > #include "qcom_scm.h"
> > +#include "qcom_tzmem.h"
> >
> > static bool download_mode = IS_ENABLED(CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT);
> > module_param(download_mode, bool, 0);
> > @@ -41,6 +45,8 @@ struct qcom_scm {
> > int scm_vote_count;
> >
> > u64 dload_mode_addr;
> > +
> > + struct qcom_tzmem_pool *mempool;
> > };
> >
> > struct qcom_scm_current_perm_info {
> > @@ -1887,6 +1893,16 @@ static int qcom_scm_probe(struct platform_device *pdev)
> > if (of_property_read_bool(pdev->dev.of_node, "qcom,sdi-enabled"))
> > qcom_scm_disable_sdi();
> >
> > + ret = qcom_tzmem_enable(__scm->dev);
> > + if (ret)
> > + return dev_err_probe(__scm->dev, ret,
> > + "Failed to enable the TrustZone memory allocator\n");
> > +
> > + __scm->mempool = devm_qcom_tzmem_pool_new(__scm->dev, SZ_256K);
>
> As we're not moving from the callers freely allocating what they need,
> to a fixed sized pool of 256kb. Please document why 256kb was choosen,
> so that we have something to fall back on when someone runs out of this
> space, or wonders "why not 128kb?".
>

If you worry about these pools being taken out of the total memory and
prefer to have a way to avoid it, I was thinking about another
build-time mode for the allocator - one where there's no pool but it
just allocates chunks using dma_alloc_coherent() like before and pool
size is ignored. Does it sound good?

Bart

> Regards,
> Bjorn
>
> > + if (IS_ERR(__scm->mempool))
> > + return dev_err_probe(__scm->dev, PTR_ERR(__scm->mempool),
> > + "Failed to create the SCM memory pool\n");
> > +
> > /*
> > * Initialize the QSEECOM interface.
> > *
> > --
> > 2.40.1
> >