Re: [PATCH] mailbox: pcc: Support HW-Reduced Communication Subspace Type 2

[Hoan Tran]

Hi Alexey,


On Tue, Apr 19, 2016 at 12:02 PM, Alexey Klimov <alexey.klimov@xxxxxxx> wrote:
> Hi Hoan,
>
> On Tue, Apr 5, 2016 at 11:14 PM, hotran <hotran@xxxxxxx> wrote:
>> ACPI 6.1 has a HW-Reduced Communication Subspace Type 2 intended for
>> use on HW-Reduce ACPI Platform, which requires read-modify-write sequence
>> to acknowledge doorbell interrupt. This patch provides the implementation
>> for the Communication Subspace Type 2.
>>
>> Signed-off-by: Hoan Tran <hotran@xxxxxxx>
>> ---
>>  drivers/mailbox/pcc.c | 384 +++++++++++++++++++++++++++++++++++++-------------
>>  include/acpi/actbl3.h |   8 +-
>>  2 files changed, 294 insertions(+), 98 deletions(-)
>>
>> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
>> index 0ddf638..4ed8153 100644
>> --- a/drivers/mailbox/pcc.c
>> +++ b/drivers/mailbox/pcc.c
>> @@ -59,6 +59,7 @@
>>  #include <linux/delay.h>
>>  #include <linux/io.h>
>>  #include <linux/init.h>
>> +#include <linux/interrupt.h>
>>  #include <linux/list.h>
>>  #include <linux/platform_device.h>
>>  #include <linux/mailbox_controller.h>
>> @@ -68,27 +69,178 @@
>>  #include "mailbox.h"
>>
>>  #define MAX_PCC_SUBSPACES      256
>> +#define MBOX_IRQ_NAME          "pcc-mbox"
>>
>> -static struct mbox_chan *pcc_mbox_channels;
>> +/**
>> + * PCC mailbox channel information
>> + *
>> + * @chan:      Pointer to mailbox communication channel
>> + * @pcc_doorbell_vaddr: PCC doorbell register address
>> + * @pcc_doorbell_ack_vaddr: PCC doorbell ack register address
>> + * @irq:       Interrupt number of the channel
>> + */
>> +struct pcc_mbox_chan {
>> +       struct mbox_chan        *chan;
>> +       void __iomem            *pcc_doorbell_vaddr;
>> +       void __iomem            *pcc_doorbell_ack_vaddr;
>> +       int                     irq;
>> +};
>>
>> -/* Array of cached virtual address for doorbell registers */
>> -static void __iomem **pcc_doorbell_vaddr;
>> +/**
>> + * PCC mailbox controller data
>> + *
>> + * @mb_ctrl:   Representation of the communication channel controller
>> + * @mbox_chan: Array of PCC mailbox channels of the controller
>> + * @chans:     Array of mailbox communication channels
>> + */
>> +struct pcc_mbox {
>> +       struct mbox_controller  mbox_ctrl;
>> +       struct pcc_mbox_chan    *mbox_chans;
>> +       struct mbox_chan        *chans;
>> +};
>> +
>> +static struct pcc_mbox pcc_mbox_ctx = {};
>>
>> -static struct mbox_controller pcc_mbox_ctrl = {};
>>  /**
>>   * get_pcc_channel - Given a PCC subspace idx, get
>> - *     the respective mbox_channel.
>> + *     the respective pcc mbox_channel.
>>   * @id: PCC subspace index.
>>   *
>>   * Return: ERR_PTR(errno) if error, else pointer
>> - *     to mbox channel.
>> + *     to pcc mbox channel.
>>   */
>> -static struct mbox_chan *get_pcc_channel(int id)
>> +static struct pcc_mbox_chan *get_pcc_channel(int id)
>>  {
>> -       if (id < 0 || id > pcc_mbox_ctrl.num_chans)
>> +       if (id < 0 || id > pcc_mbox_ctx.mbox_ctrl.num_chans)
>>                 return ERR_PTR(-ENOENT);
>>
>> -       return &pcc_mbox_channels[id];
>> +       return &pcc_mbox_ctx.mbox_chans[id];
>> +}
>> +
>> +/*
>> + * PCC can be used with perf critical drivers such as CPPC
>> + * So it makes sense to locally cache the virtual address and
>> + * use it to read/write to PCC registers such as doorbell register
>> + *
>> + * The below read_register and write_registers are used to read and
>> + * write from perf critical registers such as PCC doorbell register
>> + */
>> +static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
>> +{
>> +       int ret_val = 0;
>> +
>> +       switch (bit_width) {
>> +       case 8:
>> +               *val = readb(vaddr);
>> +               break;
>> +       case 16:
>> +               *val = readw(vaddr);
>> +               break;
>> +       case 32:
>> +               *val = readl(vaddr);
>> +               break;
>> +       case 64:
>> +               *val = readq(vaddr);
>> +               break;
>> +       default:
>> +               pr_debug("Error: Cannot read register of %u bit width",
>> +                       bit_width);
>> +               ret_val = -EFAULT;
>> +               break;
>> +       }
>> +       return ret_val;
>> +}
>> +
>> +static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
>> +{
>> +       int ret_val = 0;
>> +
>> +       switch (bit_width) {
>> +       case 8:
>> +               writeb(val, vaddr);
>> +               break;
>> +       case 16:
>> +               writew(val, vaddr);
>> +               break;
>> +       case 32:
>> +               writel(val, vaddr);
>> +               break;
>> +       case 64:
>> +               writeq(val, vaddr);
>> +               break;
>> +       default:
>> +               pr_debug("Error: Cannot write register of %u bit width",
>> +                       bit_width);
>> +               ret_val = -EFAULT;
>> +               break;
>> +       }
>> +       return ret_val;
>> +}
>> +
>> +/**
>> + * pcc_map_interrupt - Map a PCC subspace GSI to a linux IRQ number
>> + * @interrupt: GSI number.
>> + * @flags: interrupt flags
>> + *
>> + * Returns: a valid linux IRQ number on success
>> + *             0 or -EINVAL on failure
>> + */
>> +static int pcc_map_interrupt(u32 interrupt, u32 flags)
>> +{
>> +       int trigger, polarity;
>> +
>> +       if (!interrupt)
>> +               return 0;
>> +
>> +       trigger = (flags & ACPI_PCCT_INTERRUPT_MODE) ? ACPI_EDGE_SENSITIVE
>> +                       : ACPI_LEVEL_SENSITIVE;
>> +
>> +       polarity = (flags & ACPI_PCCT_INTERRUPT_POLARITY) ? ACPI_ACTIVE_LOW
>> +                       : ACPI_ACTIVE_HIGH;
>> +
>> +       return acpi_register_gsi(NULL, interrupt, trigger, polarity);
>> +}
>> +
>> +/**
>> + * pcc_mbox_irq - PCC mailbox interrupt handler
>> + */
>> +static irqreturn_t pcc_mbox_irq(int irq, void *id)
>> +{
>> +       struct acpi_generic_address *doorbell_ack;
>> +       struct acpi_pcct_hw_reduced *pcct_ss;
>> +       struct pcc_mbox_chan *pcc_chan = id;
>> +       u64 doorbell_ack_preserve;
>> +       struct mbox_chan *chan;
>> +       u64 doorbell_ack_write;
>> +       u64 doorbell_ack_val;
>> +       int ret = 0;
>
> Could you please check that you really need this initialization?
OK, will remove it
>
>> +       chan = pcc_chan->chan;
>> +       pcct_ss = chan->con_priv;
>> +
>> +       /* Clear interrupt status */
>> +       if (pcct_ss->header.type == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
>> +               doorbell_ack = &pcct_ss->doorbell_ack_register;
>> +               doorbell_ack_preserve = pcct_ss->ack_preserve_mask;
>> +               doorbell_ack_write = pcct_ss->ack_write_mask;
>> +
>> +               ret = read_register(pcc_chan->pcc_doorbell_ack_vaddr,
>> +                                   &doorbell_ack_val,
>> +                                   doorbell_ack->bit_width);
>> +               if (ret)
>> +                       return ret;
>> +
>> +               ret = write_register(pcc_chan->pcc_doorbell_ack_vaddr,
>> +                                    (doorbell_ack_val & doorbell_ack_preserve)
>> +                                       | doorbell_ack_write,
>> +                                    doorbell_ack->bit_width);
>> +               if (ret)
>> +                       return ret;
>
> Could you please check that really need to return -EFAULT here in case of error?
> Looking through irqreturn values it looks like IRQ_NONE is more proper value.
OK, change to return IRQ_NONE
>
>
>> +       }
>> +
>> +       mbox_chan_received_data(chan, NULL);
>> +
>> +       return IRQ_HANDLED;
>>  }
>>
>
> [...]
>
>>  /**
>> + * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register
>> + *             There should be one entry per PCC client.
>> + * @mbox_chans: Pointer to the PCC mailbox channel data
>> + * @pcct_ss: Pointer to the ACPI subtable header under the PCCT.
>> + *
>> + * Return: 0 for Success, else errno.
>> + *
>> + * This gets called for each entry in the PCC table.
>> + */
>> +static int pcc_parse_subspace_irq(struct pcc_mbox_chan *mbox_chans,
>> +               struct acpi_pcct_hw_reduced *pcct_ss)
>> +{
>> +       mbox_chans->irq = pcc_map_interrupt(pcct_ss->doorbell_interrupt,
>> +                                           (u32)pcct_ss->flags);
>> +       if (mbox_chans->irq <= 0) {
>> +               pr_err("PCC GSI %d not registered\n",
>> +                      pcct_ss->doorbell_interrupt);
>> +               return -EINVAL;
>> +       }
>> +
>> +       if (pcct_ss->header.type
>> +               == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
>> +               mbox_chans->pcc_doorbell_ack_vaddr = acpi_os_ioremap(
>> +                               pcct_ss->doorbell_ack_register.address,
>> +                               pcct_ss->doorbell_ack_register.bit_width / 8);
>> +               if (!mbox_chans->pcc_doorbell_ack_vaddr) {
>> +                       pr_err("Failed to ioremap PCC ACK register\n");
>> +                       return -ENOMEM;
>> +               }
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +/**
>>   * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
>>   *
>>   * Return: 0 for Success, else errno.
>> @@ -316,7 +479,8 @@ static int __init acpi_pcc_probe(void)
>>         acpi_size pcct_tbl_header_size;
>>         struct acpi_table_header *pcct_tbl;
>>         struct acpi_subtable_header *pcct_entry;
>> -       int count, i;
>> +       struct acpi_table_pcct *acpi_pcct_tbl;
>> +       int count, i, rc;
>>         acpi_status status = AE_OK;
>>
>>         /* Search for PCCT */
>> @@ -335,21 +499,29 @@ static int __init acpi_pcc_probe(void)
>>                         parse_pcc_subspace, MAX_PCC_SUBSPACES);
>>
>>         if (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);
>> +       }
>> +
>> +       if (count <= 0) {
>
> Do I understand this change correctly: in case type1 is present code flow doesn't try to parse type2 tables?
> Is presence of both type2 and type1 prohibited by specs?
Yes, it should parse all the subspace types then return error if
subspace count is <= 0.

Thanks and Regards
Hoan
>
>>                 pr_err("Error parsing PCC subspaces from PCCT\n");
>>                 return -EINVAL;
>>         }
>
> [...]
>
> Best regards,
> Alexey



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