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mailbox: pcc: optimized pcc_send_data
pcc_send_data() can be invoked during the execution of performance critical code as in cppc_cpufreq driver. With acpi_* APIs, the doorbell register accessed in pcc_send_data() if present in system memory will be searched (in cached virt to phys addr mapping), mapped, read/written and then unmapped. These operations take significant amount of time. This patch maps the performance critical doorbell register during init and then reads/writes to it directly using the mapped virtual address. This patch + similar changes to CPPC acpi driver reduce the time per freq. transition from around 200us to about 20us for the CPPC cpufreq driver Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> Acked-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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parent
77e3d86f2f
commit
8b0f578898
1 changed files with 104 additions and 7 deletions
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@ -63,6 +63,7 @@
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#include <linux/platform_device.h>
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#include <linux/mailbox_controller.h>
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#include <linux/mailbox_client.h>
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#include <linux/io-64-nonatomic-lo-hi.h>
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#include "mailbox.h"
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@ -70,6 +71,9 @@
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static struct mbox_chan *pcc_mbox_channels;
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/* Array of cached virtual address for doorbell registers */
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static void __iomem **pcc_doorbell_vaddr;
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static struct mbox_controller pcc_mbox_ctrl = {};
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/**
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* get_pcc_channel - Given a PCC subspace idx, get
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@ -166,6 +170,66 @@ void pcc_mbox_free_channel(struct mbox_chan *chan)
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}
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EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
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/*
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* PCC can be used with perf critical drivers such as CPPC
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* So it makes sense to locally cache the virtual address and
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* use it to read/write to PCC registers such as doorbell register
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*
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* The below read_register and write_registers are used to read and
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* write from perf critical registers such as PCC doorbell register
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*/
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static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
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{
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int ret_val = 0;
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switch (bit_width) {
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case 8:
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*val = readb(vaddr);
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break;
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case 16:
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*val = readw(vaddr);
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break;
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case 32:
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*val = readl(vaddr);
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break;
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case 64:
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*val = readq(vaddr);
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break;
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default:
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pr_debug("Error: Cannot read register of %u bit width",
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bit_width);
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ret_val = -EFAULT;
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break;
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}
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return ret_val;
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}
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static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
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{
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int ret_val = 0;
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switch (bit_width) {
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case 8:
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writeb(val, vaddr);
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break;
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case 16:
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writew(val, vaddr);
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break;
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case 32:
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writel(val, vaddr);
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break;
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case 64:
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writeq(val, vaddr);
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break;
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default:
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pr_debug("Error: Cannot write register of %u bit width",
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bit_width);
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ret_val = -EFAULT;
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break;
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}
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return ret_val;
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}
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/**
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* pcc_send_data - Called from Mailbox Controller code. Used
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* here only to ring the channel doorbell. The PCC client
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@ -181,21 +245,39 @@ EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
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static int pcc_send_data(struct mbox_chan *chan, void *data)
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{
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struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
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struct acpi_generic_address doorbell;
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struct acpi_generic_address *doorbell;
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u64 doorbell_preserve;
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u64 doorbell_val;
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u64 doorbell_write;
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u32 id = chan - pcc_mbox_channels;
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int ret = 0;
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doorbell = pcct_ss->doorbell_register;
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if (id >= pcc_mbox_ctrl.num_chans) {
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pr_debug("pcc_send_data: Invalid mbox_chan passed\n");
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return -ENOENT;
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}
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doorbell = &pcct_ss->doorbell_register;
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doorbell_preserve = pcct_ss->preserve_mask;
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doorbell_write = pcct_ss->write_mask;
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/* Sync notification from OS to Platform. */
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acpi_read(&doorbell_val, &doorbell);
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acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
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&doorbell);
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return 0;
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if (pcc_doorbell_vaddr[id]) {
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ret = read_register(pcc_doorbell_vaddr[id], &doorbell_val,
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doorbell->bit_width);
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if (ret)
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return ret;
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ret = write_register(pcc_doorbell_vaddr[id],
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(doorbell_val & doorbell_preserve) | doorbell_write,
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doorbell->bit_width);
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} else {
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ret = acpi_read(&doorbell_val, doorbell);
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if (ret)
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return ret;
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ret = acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
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doorbell);
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}
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return ret;
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}
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static const struct mbox_chan_ops pcc_chan_ops = {
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@ -271,14 +353,29 @@ static int __init acpi_pcc_probe(void)
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return -ENOMEM;
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}
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pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
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if (!pcc_doorbell_vaddr) {
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kfree(pcc_mbox_channels);
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return -ENOMEM;
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}
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/* Point to the first PCC subspace entry */
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pcct_entry = (struct acpi_subtable_header *) (
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(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));
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for (i = 0; i < count; i++) {
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struct acpi_generic_address *db_reg;
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struct acpi_pcct_hw_reduced *pcct_ss;
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pcc_mbox_channels[i].con_priv = pcct_entry;
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pcct_entry = (struct acpi_subtable_header *)
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((unsigned long) pcct_entry + pcct_entry->length);
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/* If doorbell is in system memory cache the virt address */
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pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry;
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db_reg = &pcct_ss->doorbell_register;
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if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
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pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address,
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db_reg->bit_width/8);
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}
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pcc_mbox_ctrl.num_chans = count;
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