On Mon, 9 Oct 2023, Shyam Sundar S K wrote: > In amd_pmc_stb_debugfs_open_v2(), the stb buffer is created based on the > num_samples and the read/write pointer offset. This holds good when the > num_samples reported by PMFW is less than S2D_TELEMETRY_BYTES_MAX; where > the stb buffer gets filled from 0th position until > S2D_TELEMETRY_BYTES_MAX - 1 based on the read/write pointer offset. > > But when the num_samples exceeds the S2D_TELEMETRY_BYTES_MAX, the current > code does not handle it well as it does not account for the cases where > the stb buffer has to filled up as a circular buffer. > > Handle this scenario into two cases, where first memcpy will have the > samples from location: > (num_samples % S2D_TELEMETRY_BYTES_MAX) - (S2D_TELEMETRY_BYTES_MAX - 1) > and next memcpy will have the newest ones i.e. > 0 - (num_samples % S2D_TELEMETRY_BYTES_MAX - 1) > > Suggested-by: Hans de Goede <hdegoede@xxxxxxxxxx> > Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx> > Signed-off-by: Sanket Goswami <Sanket.Goswami@xxxxxxx> > Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@xxxxxxx> > --- > v6->v7: > - No change > > v5->v6: > - Make changes as per Hans on v5 > - based on review-ilpo branch > > v4->v5: > - Fix exisiting code problems when reading stb buffer as a circular data > - based on review-ilpo branch > > v3->v4: > - Update code branches and commit-msg as per Ilpo's remark. > > v2->v3: > - no change > > v1->v2: > - rebase to 'review-hans' branch > - drop 2/4 of v1 > (https://patchwork.kernel.org/project/platform-driver-x86/list/?series=775324&state=%2A&archive=both) > > drivers/platform/x86/amd/pmc/pmc.c | 19 +++++++++++++------ > 1 file changed, 13 insertions(+), 6 deletions(-) > > diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c > index fdc1e104c437..e0b5d9de473a 100644 > --- a/drivers/platform/x86/amd/pmc/pmc.c > +++ b/drivers/platform/x86/amd/pmc/pmc.c > @@ -276,16 +276,23 @@ static int amd_pmc_stb_debugfs_open_v2(struct inode *inode, struct file *filp) > > flex_arr->size = fsize; > > - /* Start capturing data from the last push location */ > + /* > + * Start capturing data from the last push location. > + * This is for general cases, where the stb limits > + * are meant for standard usage. > + */ > if (num_samples > S2D_TELEMETRY_BYTES_MAX) { > - fsize = S2D_TELEMETRY_BYTES_MAX; > - stb_rdptr_offset = num_samples - fsize; > + /* First read oldest data starting 1 behind last write till end of ringbuffer */ > + stb_rdptr_offset = num_samples % S2D_TELEMETRY_BYTES_MAX; > + fsize = S2D_TELEMETRY_BYTES_MAX - stb_rdptr_offset; > + > + memcpy_fromio(flex_arr->data, dev->stb_virt_addr + stb_rdptr_offset, fsize); > + /* Second copy the newer samples from offset 0 - last write */ > + memcpy_fromio(flex_arr->data + fsize, dev->stb_virt_addr, stb_rdptr_offset); > } else { > - fsize = num_samples; > - stb_rdptr_offset = 0; > + memcpy_fromio(flex_arr->data, dev->stb_virt_addr, fsize); Is this actually correct if less than S2D_TELEMETRY_BYTES_MAX are read first time, and then the second call will use zero offset if num_samples is still less than S2D_TELEMETRY_BYTES_MAX? It seems to return duplicated entries and not the latest entries at all until num_samples wraps? -- i.
