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platform/x86/amd/pmc: Handle overflow cases where the num_samples range is higher

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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@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20231010145003.139932-2-Shyam-sundar.S-k@amd.com
[ij: renamed flex_arr -> stb_data_arr]
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
This commit is contained in:
Shyam Sundar S K 2023-10-10 20:20:02 +05:30 committed by Ilpo Järvinen
parent d9f421da6b
commit b136225746
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GPG key ID: 59AC4F6153E5CE31
1 changed files with 13 additions and 6 deletions
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19
drivers/platform/x86/amd/pmc/pmc.c
View file

@ -276,16 +276,23 @@ static int amd_pmc_stb_debugfs_open_v2(struct inode *inode, struct file *filp)
stb_data_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(stb_data_arr->data, dev->stb_virt_addr + stb_rdptr_offset, fsize);
/* Second copy the newer samples from offset 0 - last write */
memcpy_fromio(stb_data_arr->data + fsize, dev->stb_virt_addr, stb_rdptr_offset);
} else {
fsize = num_samples;
stb_rdptr_offset = 0;
memcpy_fromio(stb_data_arr->data, dev->stb_virt_addr, fsize);
}
memcpy_fromio(stb_data_arr->data, dev->stb_virt_addr + stb_rdptr_offset, fsize);
filp->private_data = stb_data_arr;
return 0;