From patchwork Sat Jan 23 01:07:17 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Prakash, Prashanth" X-Patchwork-Id: 8095241 Return-Path: X-Original-To: patchwork-linux-acpi@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 49D50BEEE5 for ; Sat, 23 Jan 2016 01:07:55 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 2F16B205CD for ; Sat, 23 Jan 2016 01:07:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 135DC205E4 for ; Sat, 23 Jan 2016 01:07:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754948AbcAWBHu (ORCPT ); Fri, 22 Jan 2016 20:07:50 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:50649 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754540AbcAWBHj (ORCPT ); Fri, 22 Jan 2016 20:07:39 -0500 Received: from smtp.codeaurora.org (localhost [127.0.0.1]) by smtp.codeaurora.org (Postfix) with ESMTP id 493CA60269; Sat, 23 Jan 2016 01:07:39 +0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 3CC4960470; Sat, 23 Jan 2016 01:07:39 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from pprakash-lnx.qualcomm.com (unknown [129.46.15.62]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: pprakash@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id CB0716045B; Sat, 23 Jan 2016 01:07:37 +0000 (UTC) From: Prashanth Prakash To: rjw@rjwysocki.net Cc: ashwin.chaugule@linaro.org, linux-acpi@vger.kernel.org, linaro-acpi@lists.linaro.org, Prashanth Prakash Subject: [PATCH V2 1/4] ACPI / CPPC: Optimize PCC Read Write operations Date: Fri, 22 Jan 2016 18:07:17 -0700 Message-Id: <1453511240-20792-2-git-send-email-pprakash@codeaurora.org> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1453511240-20792-1-git-send-email-pprakash@codeaurora.org> References: <1453511240-20792-1-git-send-email-pprakash@codeaurora.org> X-Virus-Scanned: ClamAV using ClamSMTP Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Ashwin Chaugule Previously the send_pcc_cmd() code checked if the PCC operation had completed before returning from the function. This check was performed regardless of the PCC op type (i.e. Read/Write). Knowing the type of cmd can be used to optimize the check and avoid needless waiting. e.g. with Write ops, the actual Writing is done before calling send_pcc_cmd(). And the subsequent Writes will check if the channel is free at the entry of send_pcc_cmd() anyway. However, for Read cmds, we need to wait for the cmd completion bit to be flipped, since the actual Read ops follow after returning from the send_pcc_cmd(). So, only do the looping check at the end for Read ops. Also, instead of using udelay() calls, use ktime as a means to check for deadlines. The current deadline in which the Remote should flip the cmd completion bit is defined as N * Nominal latency. Where N is arbitrary and large enough to work on slow emulators and Nominal latency comes from the ACPI table (PCCT). This helps in working around the CONFIG_HZ effects on udelay() and also avoids needing different ACPI tables for Silicon and Emulation platforms. Signed-off-by: Ashwin Chaugule Signed-off-by: Prashanth Prakash --- drivers/acpi/cppc_acpi.c | 102 ++++++++++++++++++++++++++++++++++------------- 1 file changed, 74 insertions(+), 28 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 6730f96..36c3e4d 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -39,6 +39,7 @@ #include #include +#include #include /* @@ -63,25 +64,56 @@ static struct mbox_chan *pcc_channel; static void __iomem *pcc_comm_addr; static u64 comm_base_addr; static int pcc_subspace_idx = -1; -static u16 pcc_cmd_delay; static bool pcc_channel_acquired; +static ktime_t deadline; /* * Arbitrary Retries in case the remote processor is slow to respond - * to PCC commands. + * to PCC commands. Keeping it high enough to cover emulators where + * the processors run painfully slow. */ #define NUM_RETRIES 500 +static int check_pcc_chan(void) +{ + int result = -EIO; + struct acpi_pcct_shared_memory *generic_comm_base = + (struct acpi_pcct_shared_memory *) pcc_comm_addr; + ktime_t next_deadline = ktime_add(ktime_get(), deadline); + int retries = 0; + + /* Retry in case the remote processor was too slow to catch up. */ + while (!ktime_after(ktime_get(), next_deadline)) { + if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { + result = 0; + break; + } + /* + * Reducing the bus traffic in case this loop takes longer than + * a few retries. + */ + udelay(3); + retries++; + } + + return result; +} + static int send_pcc_cmd(u16 cmd) { - int retries, result = -EIO; - struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv; + int ret = -EIO; struct acpi_pcct_shared_memory *generic_comm_base = (struct acpi_pcct_shared_memory *) pcc_comm_addr; - u32 cmd_latency = pcct_ss->latency; - /* Min time OS should wait before sending next command. */ - udelay(pcc_cmd_delay); + /* + * For CMD_WRITE we know for a fact the caller should have checked + * the channel before writing to PCC space + */ + if (cmd == CMD_READ) { + ret = check_pcc_chan(); + if (ret) + return ret; + } /* Write to the shared comm region. */ writew(cmd, &generic_comm_base->command); @@ -90,26 +122,25 @@ static int send_pcc_cmd(u16 cmd) writew(0, &generic_comm_base->status); /* Ring doorbell */ - result = mbox_send_message(pcc_channel, &cmd); - if (result < 0) { + ret = mbox_send_message(pcc_channel, &cmd); + if (ret < 0) { pr_err("Err sending PCC mbox message. cmd:%d, ret:%d\n", - cmd, result); - return result; + cmd, ret); + return ret; } - /* Wait for a nominal time to let platform process command. */ - udelay(cmd_latency); - - /* Retry in case the remote processor was too slow to catch up. */ - for (retries = NUM_RETRIES; retries > 0; retries--) { - if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { - result = 0; - break; - } - } + /* + * For READs we need to ensure the cmd completed to ensure + * the ensuing read()s can proceed. For WRITEs we dont care + * because the actual write()s are done before coming here + * and the next READ or WRITE will check if the channel + * is busy/free at the entry of this call. + */ + if (cmd == CMD_READ) + ret = check_pcc_chan(); - mbox_client_txdone(pcc_channel, result); - return result; + mbox_client_txdone(pcc_channel, ret); + return ret; } static void cppc_chan_tx_done(struct mbox_client *cl, void *msg, int ret) @@ -306,6 +337,7 @@ static int register_pcc_channel(int pcc_subspace_idx) { struct acpi_pcct_hw_reduced *cppc_ss; unsigned int len; + u64 usecs_lat; if (pcc_subspace_idx >= 0) { pcc_channel = pcc_mbox_request_channel(&cppc_mbox_cl, @@ -335,7 +367,14 @@ static int register_pcc_channel(int pcc_subspace_idx) */ comm_base_addr = cppc_ss->base_address; len = cppc_ss->length; - pcc_cmd_delay = cppc_ss->min_turnaround_time; + + /* + * cppc_ss->latency is just a Nominal value. In reality + * the remote processor could be much slower to reply. + * So add an arbitrary amount of wait on top of Nominal. + */ + usecs_lat = NUM_RETRIES * cppc_ss->latency; + deadline = ns_to_ktime(usecs_lat * NSEC_PER_USEC); pcc_comm_addr = acpi_os_ioremap(comm_base_addr, len); if (!pcc_comm_addr) { @@ -604,7 +643,7 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps) (ref_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) || (nom_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) { /* Ring doorbell once to update PCC subspace */ - if (send_pcc_cmd(CMD_READ)) { + if (send_pcc_cmd(CMD_READ) < 0) { ret = -EIO; goto out_err; } @@ -662,7 +701,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) if ((delivered_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) || (reference_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) { /* Ring doorbell once to update PCC subspace */ - if (send_pcc_cmd(CMD_READ)) { + if (send_pcc_cmd(CMD_READ) < 0) { ret = -EIO; goto out_err; } @@ -713,6 +752,13 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) spin_lock(&pcc_lock); + /* If this is PCC reg, check if channel is free before writing */ + if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) { + ret = check_pcc_chan(); + if (ret) + goto busy_channel; + } + /* * Skip writing MIN/MAX until Linux knows how to come up with * useful values. @@ -722,10 +768,10 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) /* Is this a PCC reg ?*/ if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) { /* Ring doorbell so Remote can get our perf request. */ - if (send_pcc_cmd(CMD_WRITE)) + if (send_pcc_cmd(CMD_WRITE) < 0) ret = -EIO; } - +busy_channel: spin_unlock(&pcc_lock); return ret;