Re: [PATCHv15 5/9] lib: Add register read/write tracing support

[Sai Prakash Ranjan]

On 6/14/2022 8:02 PM, Steven Rostedt wrote:
> On Wed, 18 May 2022 22:14:14 +0530
> Sai Prakash Ranjan <quic_saipraka@xxxxxxxxxxx> wrote:
>
> > From: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxx>
> > Co-developed-by: Sai Prakash Ranjan <quic_saipraka@xxxxxxxxxxx>
> > Signed-off-by: Sai Prakash Ranjan <quic_saipraka@xxxxxxxxxxx>
> > ---
>  From a tracing point of view, I do not see anything wrong with this patch.
>
> Acked-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
>
> -- Steve

Thanks Steve.

Hi Arnd, I hope we can take this series in your tree or let me know if anything else is pending?

Thanks,
Sai