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> Signed-off-by: Sanket Goswami <Sanket.Goswami@xxxxxxx> Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@xxxxxxx> --- 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); } - memcpy_fromio(flex_arr->data, dev->stb_virt_addr + stb_rdptr_offset, fsize); filp->private_data = flex_arr; return 0; -- 2.25.1
