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SubjectRe: [PATCHv15 5/9] lib: Add register read/write tracing support
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Hi Steve,

On 5/18/2022 10:14 PM, Sai Prakash Ranjan wrote:
> From: Prasad Sodagudi <psodagud@codeaurora.org>
>
> Generic MMIO read/write i.e., __raw_{read,write}{b,l,w,q} accessors
> are typically used to read/write from/to memory mapped registers
> and can cause hangs or some undefined behaviour in following few
> cases,
>
> * If the access to the register space is unclocked, for example: if
> there is an access to multimedia(MM) block registers without MM
> clocks.
>
> * If the register space is protected and not set to be accessible from
> non-secure world, for example: only EL3 (EL: Exception level) access
> is allowed and any EL2/EL1 access is forbidden.
>
> * If xPU(memory/register protection units) is controlling access to
> certain memory/register space for specific clients.
>
> and more...
>
> Such cases usually results in instant reboot/SErrors/NOC or interconnect
> hangs and tracing these register accesses can be very helpful to debug
> such issues during initial development stages and also in later stages.
>
> So use ftrace trace events to log such MMIO register accesses which
> provides rich feature set such as early enablement of trace events,
> filtering capability, dumping ftrace logs on console and many more.
>
> Sample output:
>
> rwmmio_write: __qcom_geni_serial_console_write+0x160/0x1e0 width=32 val=0xa0d5d addr=0xfffffbfffdbff700
> rwmmio_post_write: __qcom_geni_serial_console_write+0x160/0x1e0 width=32 val=0xa0d5d addr=0xfffffbfffdbff700
> rwmmio_read: qcom_geni_serial_poll_bit+0x94/0x138 width=32 addr=0xfffffbfffdbff610
> rwmmio_post_read: qcom_geni_serial_poll_bit+0x94/0x138 width=32 val=0x0 addr=0xfffffbfffdbff610
>
> Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
> Co-developed-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>
> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>
> ---
> arch/Kconfig | 3 ++
> arch/arm64/Kconfig | 1 +
> include/trace/events/rwmmio.h | 97 +++++++++++++++++++++++++++++++++++
> lib/Kconfig | 7 +++
> lib/Makefile | 2 +
> lib/trace_readwrite.c | 47 +++++++++++++++++
> 6 files changed, 157 insertions(+)
> create mode 100644 include/trace/events/rwmmio.h
> create mode 100644 lib/trace_readwrite.c

How does this version look?

Thanks,
Sai

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