Re: [PATCH v2 11/11] firmware: qcom: scm: enable SHM bridge

Bartosz Golaszewski
2023-09-28T18:28:55Z

On Thu, Sep 28, 2023 at 7:10 PM Elliot Berman <quic_eberman@quicinc.com> wrote:
>
>
>
> On 9/28/2023 2:20 AM, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > Extens the SCM memory allocator with using the SHM Bridge feature if
> > available on the platform. This makes the trustzone only use dedicated
> > buffers for SCM calls. We map the entire SCM genpool as a bridge.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > ---
> > drivers/firmware/qcom/qcom_scm-mem.c | 42 ++++++++++++++++++++++++++--
> > 1 file changed, 39 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/firmware/qcom/qcom_scm-mem.c b/drivers/firmware/qcom/qcom_scm-mem.c
> > index eafecbe23770..12b12b15f46f 100644
> > --- a/drivers/firmware/qcom/qcom_scm-mem.c
> > +++ b/drivers/firmware/qcom/qcom_scm-mem.c
> > @@ -16,6 +16,8 @@
> >
> > #include "qcom_scm.h"
> >
> > +#define QCOM_SHM_BRIDGE_NUM_VM_SHIFT 9
> > +
> > static size_t qcom_scm_mem_pool_size = SZ_2M;
> > module_param_named(qcom_scm_mem_pool_size, qcom_scm_mem_pool_size,
> > ulong, 0400);
> > @@ -108,8 +110,24 @@ phys_addr_t qcom_scm_mem_to_phys(void *vaddr)
> > return chunk->paddr;
> > }
> >
> > +static int qcom_scm_mem_shm_bridge_create(void)
> > +{
> > + uint64_t pfn_and_ns_perm, ipfn_and_s_perm, size_and_flags, ns_perms;
> > +
> > + ns_perms = (QCOM_SCM_PERM_WRITE | QCOM_SCM_PERM_READ);
> > + pfn_and_ns_perm = (u64)qcom_scm_mem.pbase | ns_perms;
> > + ipfn_and_s_perm = (u64)qcom_scm_mem.pbase | ns_perms;
> > + size_and_flags = qcom_scm_mem.size | (1 << QCOM_SHM_BRIDGE_NUM_VM_SHIFT);
> > +
> > + return qcom_scm_create_shm_bridge(qcom_scm_mem.dev, pfn_and_ns_perm,
> > + ipfn_and_s_perm, size_and_flags,
> > + QCOM_SCM_VMID_HLOS);
> > +}
> > +
> > int qcom_scm_mem_enable(struct device *dev)
> > {
> > + int ret;
> > +
> > INIT_RADIX_TREE(&qcom_scm_mem.chunks, GFP_ATOMIC);
> > spin_lock_init(&qcom_scm_mem.lock);
> > qcom_scm_mem.dev = dev;
> > @@ -128,7 +146,25 @@ int qcom_scm_mem_enable(struct device *dev)
> >
> > gen_pool_set_algo(qcom_scm_mem.pool, gen_pool_best_fit, NULL);
> >
> > - return gen_pool_add_virt(qcom_scm_mem.pool,
> > - (unsigned long)qcom_scm_mem.vbase,
> > - qcom_scm_mem.pbase, qcom_scm_mem.size, -1);
> > + ret = gen_pool_add_virt(qcom_scm_mem.pool,
> > + (unsigned long)qcom_scm_mem.vbase,
> > + qcom_scm_mem.pbase, qcom_scm_mem.size, -1);
> > + if (ret)
> > + return ret;
> > +
> > + ret = qcom_scm_enable_shm_bridge();
> > + if (ret) {
> > + if (ret == EOPNOTSUPP)
> > + dev_info(dev, "SHM Bridge not supported\n");
> > + else
> > + return ret;
> > + } else {
> > + ret = qcom_scm_mem_shm_bridge_create();
> > + if (ret)
> > + return ret;
> > +
> > + dev_info(dev, "SHM Bridge enabled\n");
>
> Do you need to add clean up (deletion) of the SHM bridge on driver remove?
>
> One easy approach I could think: implemnet devm_qcom_scm_mem_shm_bridge_create
> which calls qcom_scm_delete_shm_bridge on the clean up
> (qcom_scm_delete_shm_bridge implemented in downstream, not in this series).
>

There wouldn't be any user of these symbols yet so let's think about
it when there's a valid use-case upstream.

Bart

> > + }
> > +
> > + return 0;
> > }