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Date: Tue, 14 Jun 2022 10:32:05 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Sai Prakash Ranjan <quic_saipraka@...cinc.com> Cc: <arnd@...db.de>, <catalin.marinas@....com>, <gregkh@...uxfoundation.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <coresight@...ts.linaro.org>, <suzuki.poulose@....com>, <maz@...nel.org>, <quic_psodagud@...cinc.com>, <quic_tsoni@...cinc.com>, <will@...nel.org>, Prasad Sodagudi <psodagud@...eaurora.org> Subject: Re: [PATCHv15 5/9] lib: Add register read/write tracing support On Wed, 18 May 2022 22:14:14 +0530 Sai Prakash Ranjan <quic_saipraka@...cinc.com> wrote: > From: Prasad Sodagudi <psodagud@...eaurora.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@...eaurora.org> > Co-developed-by: Sai Prakash Ranjan <quic_saipraka@...cinc.com> > Signed-off-by: Sai Prakash Ranjan <quic_saipraka@...cinc.com> > --- >From a tracing point of view, I do not see anything wrong with this patch. Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org> -- Steve
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