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Message-ID: <20210322212047.GA1684006@xps15>
Date: Mon, 22 Mar 2021 15:20:47 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
mike.leach@...aro.org, anshuman.khandual@....com,
leo.yan@...aro.org
Subject: Re: [PATCH v4 18/19] coresight: sink: Add TRBE driver
On Thu, Feb 25, 2021 at 07:35:42PM +0000, Suzuki K Poulose wrote:
> From: Anshuman Khandual <anshuman.khandual@....com>
>
> Trace Buffer Extension (TRBE) implements a trace buffer per CPU which is
> accessible via the system registers. The TRBE supports different addressing
> modes including CPU virtual address and buffer modes including the circular
> buffer mode. The TRBE buffer is addressed by a base pointer (TRBBASER_EL1),
> an write pointer (TRBPTR_EL1) and a limit pointer (TRBLIMITR_EL1). But the
> access to the trace buffer could be prohibited by a higher exception level
> (EL3 or EL2), indicated by TRBIDR_EL1.P. The TRBE can also generate a CPU
> private interrupt (PPI) on address translation errors and when the buffer
> is full. Overall implementation here is inspired from the Arm SPE driver.
>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> Changes:
> - Replaced TRBLIMITR_LIMIT_SHIFT with TRBBASER_BASE_SHIFT in set_trbe_base_pointer()
> - Dropped TRBBASER_BASE_MASK and TRBBASER_BASE_SHIFT from get_trbe_base_pointer()
> - Indentation changes for TRBE_BSC_NOT_[STOPPED|FILLED|TRIGGERED] definitions
> - Moved DECLARE_PER_CPU(...., csdev_sink) into coresight-priv.h
> - Moved isb() from trbe_enable_hw() into set_trbe_limit_pointer_enabled()
> - Dropped the space after type casting before vmap()
> - Return 0 instead of EINVAL in arm_trbe_update_buffer()
> - Add a comment in trbe_handle_overflow()
> - Add a comment in arm_trbe_cpu_startup()
> - Unregister coresight TRBE device when not supported
> - Fix potential NULL handle dereference in IRQ handler with a spurious IRQ
> - Read TRBIDR after is_trbe_programmable() in arm_trbe_probe_coresight_cpu()
> - Replaced and modified trbe_drain_and_disable_local() in IRQ handler
> - Updated arm_trbe_update_buffer() for handling a missing interrupt
> - Dropped kfree() for all devm_xxx() allocated buffer
> - Dropped additional blank line in documentation coresight/coresight-trbe.rst
> - Added Documentation/ABI/testing/sysfs-bus-coresight-devices-trbe
> - Changed CONFIG_CORESIGHT_TRBE options, dependencies and helper write up
> - Added comment for irq_work_run()
> - Updated comment for minumum buffer length in arm_trbe_alloc_buffer()
> - Dropped redundant smp_processor_id() from arm_trbe_probe_coresight_cpu()
> - Fixed indentation in arm_trbe_probe_cpuhp()
> - Added static for arm_trbe_free_buffer()
> - Added comment for trbe_base element in trbe_buf structure
> - Dropped IS_ERR() check from vmap() returned pointer
> - Added WARN_ON(trbe_csdev) in arm_trbe_probe_coresight_cpu()
> - Changed TRBE device names from arm_trbeX to just trbeX
> - Dropped unused argument perf_output_handle from trbe_get_fault_act()
> - Dropped IS_ERR() from kzalloc_node()/kcalloc() buffer in arm_trbe_alloc_buffer()
> - Dropped IS_ERR() and return -ENOMEM in arm_trbe_probe_coresight()
> - Moved TRBE HW disabling before coresight cleanup in arm_trbe_remove_coresight_cpu()
> - Changed error return codes from arm_trbe_probe_irq()
> - Changed error return codes from arm_trbe_device_probe()
> - Changed arm_trbe_remove_coresight() order in arm_trbe_device_remove()
> - Changed TRBE CPU support probe/remove sequence with for_each_cpu() iterator
> - Changed coresight_register() in arm_trbe_probe_coresight_cpu()
> - Changed error return code when cpuhp_setup_state_multi() fails in arm_trbe_probe_cpuhp()
> - Changed error return code when cpuhp_state_add_instance() fails in arm_trbe_probe_cpuhp()
> - Changed trbe_dbm as trbe_flag including its sysfs interface
> - Handle race between update_buffer & IRQ handler
> - Rework and split the TRBE probe to avoid lockdep due to memory allocation
> from IPI calls (via coresight_register())
> - Fix handle->head updat for snapshot mode.
All of the above make this driver much easier to read.
> ---
> .../testing/sysfs-bus-coresight-devices-trbe | 14 +
> .../trace/coresight/coresight-trbe.rst | 38 +
> drivers/hwtracing/coresight/Kconfig | 14 +
> drivers/hwtracing/coresight/Makefile | 1 +
> drivers/hwtracing/coresight/coresight-trbe.c | 1149 +++++++++++++++++
> drivers/hwtracing/coresight/coresight-trbe.h | 153 +++
> 6 files changed, 1369 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-trbe
> create mode 100644 Documentation/trace/coresight/coresight-trbe.rst
> create mode 100644 drivers/hwtracing/coresight/coresight-trbe.c
> create mode 100644 drivers/hwtracing/coresight/coresight-trbe.h
>
[...]
> +
> +static void *arm_trbe_alloc_buffer(struct coresight_device *csdev,
> + struct perf_event *event, void **pages,
> + int nr_pages, bool snapshot)
> +{
> + struct trbe_buf *buf;
> + struct page **pglist;
> + int i;
> +
> + /*
> + * TRBE LIMIT and TRBE WRITE pointers must be page aligned. But with
> + * just a single page, there would not be any room left while writing
> + * into a partially filled TRBE buffer after the page size alignment.
> + * Hence restrict the minimum buffer size as two pages.
> + */
> + if (nr_pages < 2)
> + return NULL;
> +
> + buf = kzalloc_node(sizeof(*buf), GFP_KERNEL, trbe_alloc_node(event));
> + if (!buf)
> + return ERR_PTR(-ENOMEM);
> +
> + pglist = kcalloc(nr_pages, sizeof(*pglist), GFP_KERNEL);
> + if (!pglist) {
> + kfree(buf);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + for (i = 0; i < nr_pages; i++)
> + pglist[i] = virt_to_page(pages[i]);
> +
> + buf->trbe_base = (unsigned long)vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL);
> + if (!buf->trbe_base) {
> + kfree(pglist);
> + kfree(buf);
> + return ERR_PTR(buf->trbe_base);
return ERR_PTR(-ENOMEM);
> + }
> + buf->trbe_limit = buf->trbe_base + nr_pages * PAGE_SIZE;
> + buf->trbe_write = buf->trbe_base;
> + buf->snapshot = snapshot;
> + buf->nr_pages = nr_pages;
> + buf->pages = pages;
> + kfree(pglist);
> + return buf;
> +}
> +
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