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Date:   Fri, 27 Apr 2018 13:16:52 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Al Stone <ahs3@...hat.com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>
Subject: Re: [PATCH v2 3/3] mailbox: ACPI: erroneous error message when
 parsing the ACPI PCCT

On Tue, Apr 24, 2018 at 9:35 PM, Al Stone <ahs3@...hat.com> wrote:
> There have been multiple reports of the following error message:
>
> [    0.068293] Error parsing PCC subspaces from PCCT
>

[cut]

>
> Tested on my personal laptop which showed the error previously; the
> error message no longer appears and the laptop appears to operate
> normally.
>
> Signed-off-by: Al Stone <ahs3@...hat.com>
> Cc: Jassi Brar <jassisinghbrar@...il.com>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Len Brown <lenb@...nel.org>
> ---
>  drivers/mailbox/pcc.c | 99 +++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 73 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index 3ef7f036ceea..cc77a2f1694f 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -372,6 +372,35 @@ static const struct mbox_chan_ops pcc_chan_ops = {
>         .send_data = pcc_send_data,
>  };
>
> +/*
> + *
> + * count_pcc_subspaces -- Count the PCC subspaces that are not used in
> + *             reduced hardware systems.

One line here, please.

> + * @header: Pointer to the ACPI subtable header under the PCCT.
> + * @end: End of subtable entry.
> + *
> + * Return: 0 for Success, else errno.

The only errno returned appears to be -EINVAL, so maybe say when that
is returned and then "or 0 otherwise".

> + *
> + * This gets called for each entry in the PCC table.
> + */
> +static int count_pcc_subspaces(struct acpi_subtable_header *header,
> +               const unsigned long end)
> +{
> +       struct acpi_pcct_subspace *pcct_ss =
> +                               (struct acpi_pcct_subspace *) header;

This can be one line (ignore warnings from checkpatch about that).

> +
> +       if ((pcct_ss->header.type <= ACPI_PCCT_TYPE_RESERVED) &&
> +           (pcct_ss->header.type != ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE) &&
> +           (pcct_ss->header.type !=
> +                               ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2)) {

This can be one line too.

> +               pr_warn("PCCT count: useful subtype = %d\n",
> +                       pcct_ss->header.type);

Why pr_warn()?

> +               return 0;
> +       }
> +       pr_warn("PCCT count: unwanted subtype = %d\n", pcct_ss->header.type);
> +       return -EINVAL;
> +}
> +
>  /**
>   * parse_pcc_subspace - Parse the PCC table and verify PCC subspace
>   *             entries. There should be one entry per PCC client.
> @@ -395,10 +424,14 @@ static int parse_pcc_subspace(struct acpi_subtable_header *header,
>                     && (pcct_ss->header.type !=
>                                 ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2)) {
>                         pr_err("Incorrect PCC Subspace type detected\n");
> +                       pr_warn("PCCT parse: unwanted subtype = %d\n",
> +                               pcct_ss->header.type);

Maybe merge the two messages?

>                         return -EINVAL;
>                 }
>         }
>
> +       pcct_ss = (struct acpi_pcct_hw_reduced *) header;
> +       pr_warn("PCCT parse: useful subtype = %d\n", pcct_ss->header.type);
>         return 0;
>  }
>
> @@ -449,8 +482,8 @@ static int __init acpi_pcc_probe(void)
>         struct acpi_table_header *pcct_tbl;
>         struct acpi_subtable_header *pcct_entry;
>         struct acpi_table_pcct *acpi_pcct_tbl;
> +       struct acpi_subtable_proc proc[ACPI_PCCT_TYPE_RESERVED];
>         int count, i, rc;
> -       int sum = 0;
>         acpi_status status = AE_OK;
>
>         /* Search for PCCT */
> @@ -459,43 +492,50 @@ static int __init acpi_pcc_probe(void)
>         if (ACPI_FAILURE(status) || !pcct_tbl)
>                 return -ENODEV;
>
> -       count = acpi_table_parse_entries(ACPI_SIG_PCCT,
> -                       sizeof(struct acpi_table_pcct),
> -                       ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
> -                       parse_pcc_subspace, MAX_PCC_SUBSPACES);
> -       sum += (count > 0) ? count : 0;
> -
> -       count = acpi_table_parse_entries(ACPI_SIG_PCCT,
> -                       sizeof(struct acpi_table_pcct),
> -                       ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2,
> -                       parse_pcc_subspace, MAX_PCC_SUBSPACES);
> -       sum += (count > 0) ? count : 0;
> +       /* Set up the subtable handlers */
> +       for (i = ACPI_PCCT_TYPE_GENERIC_SUBSPACE;
> +            i < ACPI_PCCT_TYPE_RESERVED;

I would append the line below to this one.

> +            i++) {
> +               proc[i].id = i;
> +               if (i == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE ||
> +                   i == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2)
> +                       proc[i].handler = parse_pcc_subspace;
> +               else
> +                       proc[i].handler = count_pcc_subspaces;
> +               proc[i].count = 0;

Why don't you move the count initialization above the if ()?

> +       }
>
> -       if (sum == 0 || sum >= MAX_PCC_SUBSPACES) {
> -               pr_err("Error parsing PCC subspaces from PCCT\n");
> +       count = acpi_table_parse_entries_array(ACPI_SIG_PCCT,
> +                       sizeof(struct acpi_table_pcct), proc,
> +                       ACPI_PCCT_TYPE_RESERVED, MAX_PCC_SUBSPACES);
> +       if (count == 0) {
> +               pr_warn("PCCT provided but has no subspaces defined\n");
> +               return -EINVAL;
> +       } else if (count > MAX_PCC_SUBSPACES) {
> +               pr_warn("Too many PCC subspaces defined in PCCT\n");

Do we need such detailed information to be printed here?  If you said
something like "Invalid PCCT format", you could merge the two if ()
branches.

>                 return -EINVAL;
>         }
>
>         pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
> -                       sum, GFP_KERNEL);
> +                       count, GFP_KERNEL);

One line, please.

>         if (!pcc_mbox_channels) {
>                 pr_err("Could not allocate space for PCC mbox channels\n");
>                 return -ENOMEM;
>         }
>
> -       pcc_doorbell_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
> +       pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
>         if (!pcc_doorbell_vaddr) {
>                 rc = -ENOMEM;
>                 goto err_free_mbox;
>         }
>
> -       pcc_doorbell_ack_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
> +       pcc_doorbell_ack_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
>         if (!pcc_doorbell_ack_vaddr) {
>                 rc = -ENOMEM;
>                 goto err_free_db_vaddr;
>         }
>
> -       pcc_doorbell_irq = kcalloc(sum, sizeof(int), GFP_KERNEL);
> +       pcc_doorbell_irq = kcalloc(count, sizeof(int), GFP_KERNEL);
>         if (!pcc_doorbell_irq) {
>                 rc = -ENOMEM;
>                 goto err_free_db_ack_vaddr;
> @@ -509,18 +549,25 @@ static int __init acpi_pcc_probe(void)
>         if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL)
>                 pcc_mbox_ctrl.txdone_irq = true;
>
> -       for (i = 0; i < sum; i++) {
> +       for (i = 0; i < count; i++) {
>                 struct acpi_generic_address *db_reg;
> -               struct acpi_pcct_hw_reduced *pcct_ss;
> +               struct acpi_pcct_subspace *pcct_ss;
>                 pcc_mbox_channels[i].con_priv = pcct_entry;
>
> -               pcct_ss = (struct acpi_pcct_hw_reduced *) pcct_entry;
> +               if (pcct_entry->type == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE ||
> +                   pcct_entry->type ==
> +                               ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {

Again, please merge the two lines above.

> +                       struct acpi_pcct_hw_reduced *pcct_hrss;
> +
> +                       pcct_hrss = (struct acpi_pcct_hw_reduced *) pcct_entry;
>
> -               if (pcc_mbox_ctrl.txdone_irq) {
> -                       rc = pcc_parse_subspace_irq(i, pcct_ss);
> -                       if (rc < 0)
> -                               goto err;
> +                       if (pcc_mbox_ctrl.txdone_irq) {
> +                               rc = pcc_parse_subspace_irq(i, pcct_hrss);
> +                               if (rc < 0)
> +                                       goto err;
> +                       }
>                 }
> +               pcct_ss = (struct acpi_pcct_subspace *) pcct_entry;
>
>                 /* If doorbell is in system memory cache the virt address */
>                 db_reg = &pcct_ss->doorbell_register;
> @@ -531,7 +578,7 @@ static int __init acpi_pcc_probe(void)
>                         ((unsigned long) pcct_entry + pcct_entry->length);
>         }
>
> -       pcc_mbox_ctrl.num_chans = sum;
> +       pcc_mbox_ctrl.num_chans = count;
>
>         pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
>
> --

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