From patchwork Thu Nov 5 07:26:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brad Campbell X-Patchwork-Id: 11883409 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 788A914B4 for ; Thu, 5 Nov 2020 07:27:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DA1220825 for ; Thu, 5 Nov 2020 07:27:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fnarfbargle.com header.i=@fnarfbargle.com header.b="XqgGGzdv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729314AbgKEH05 (ORCPT ); Thu, 5 Nov 2020 02:26:57 -0500 Received: from ns3.fnarfbargle.com ([103.4.19.87]:57042 "EHLO ns3.fnarfbargle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729902AbgKEH05 (ORCPT ); Thu, 5 Nov 2020 02:26:57 -0500 Received: from srv.home ([10.8.0.1] ident=heh14688) by ns3.fnarfbargle.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1kaZf9-0008Rr-4W; Thu, 05 Nov 2020 15:26:27 +0800 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=fnarfbargle.com; s=mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:References:Cc:To:From:Subject; bh=5HLunmG7HJyacgBOcrKunL1DELEhyW1eh5P0MUqSsAw=; b=XqgGGzdv5ysysxJK7HbcD7++MRD3mdr+ff9NizyyQBTsAKFB/zYlx6y1GzyifqV7+H+bLrziNTgXztZ4EqUzebtFABpTYJPZI7g3XBRl765c+wCb3v/QddL/T78YxtUnUzpvVlVbFnd5G4L46PNEQXFZBoYQ5qWImRxz8myMeNU=; Subject: [PATCH] applesmc: Re-work SMC comms v2 From: Brad Campbell To: Guenter Roeck , Andreas Kemnade , Jean Delvare Cc: Arnd Bergmann , rydberg@bitmath.org, linux-hwmon@vger.kernel.org, "linux-kernel@vger.kernel.org" , hns@goldelico.com References: <20200930105442.3f642f6c@aktux> <20200930164446.GB219887@roeck-us.net> <20201002002251.28462e64@aktux> <7543ef85-727d-96c3-947e-5b18e9e6c44d@roeck-us.net> <20201006090226.4275c824@kemnade.info> <68467f1b-cea1-47ea-a4d4-8319214b072a@fnarfbargle.com> <20201104142057.62493c12@aktux> <2436afef-99c6-c352-936d-567bf553388c@fnarfbargle.com> <7a085650-2399-08c0-3c4d-6cd1fa28a365@roeck-us.net> <10027199-5d31-93e7-9bd8-7baaebff8b71@roeck-us.net> <70331f82-35a1-50bd-685d-0b06061dd213@fnarfbargle.com> Message-ID: <3c72ccc3-4de1-b5d0-423d-7b8c80991254@fnarfbargle.com> Date: Thu, 5 Nov 2020 18:26:24 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <70331f82-35a1-50bd-685d-0b06061dd213@fnarfbargle.com> Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org Commit fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") introduced an issue whereby communication with the SMC became unreliable with write errors like : [ 120.378614] applesmc: send_byte(0x00, 0x0300) fail: 0x40 [ 120.378621] applesmc: LKSB: write data fail [ 120.512782] applesmc: send_byte(0x00, 0x0300) fail: 0x40 [ 120.512787] applesmc: LKSB: write data fail The original code appeared to be timing sensitive and was not reliable with the timing changes in the aforementioned commit. This patch re-factors the SMC communication to remove the timing dependencies and restore function with the changes previously committed. v2 : Address logic and coding style Reported-by: Andreas Kemnade Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") Signed-off-by: Brad Campbell Tested-by: Andreas Kemnade # MacBookAir6,2 Reported-by: Andreas Kemnade Signed-off-by: Brad Campbell Signed-off-by: Henrik Rydberg diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c index a18887990f4a..de890f3ec12f 100644 --- a/drivers/hwmon/applesmc.c +++ b/drivers/hwmon/applesmc.c @@ -42,6 +42,11 @@ #define APPLESMC_MAX_DATA_LENGTH 32 +/* Apple SMC status bits */ +#define SMC_STATUS_AWAITING_DATA BIT(0) /* SMC has data waiting */ +#define SMC_STATUS_IB_CLOSED BIT(1) /* Will ignore any input */ +#define SMC_STATUS_BUSY BIT(2) /* Command in progress */ + /* wait up to 128 ms for a status change. */ #define APPLESMC_MIN_WAIT 0x0010 #define APPLESMC_RETRY_WAIT 0x0100 @@ -151,65 +156,69 @@ static unsigned int key_at_index; static struct workqueue_struct *applesmc_led_wq; /* - * wait_read - Wait for a byte to appear on SMC port. Callers must - * hold applesmc_lock. + * Wait for specific status bits with a mask on the SMC + * Used before and after writes, and before reads */ -static int wait_read(void) + +static int wait_status(u8 val, u8 mask) { unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; u8 status; int us; for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - usleep_range(us, us * 16); status = inb(APPLESMC_CMD_PORT); - /* read: wait for smc to settle */ - if (status & 0x01) + if ((status & mask) == val) return 0; /* timeout: give up */ if (time_after(jiffies, end)) break; - } - - pr_warn("wait_read() fail: 0x%02x\n", status); + usleep_range(us, us * 16); + } return -EIO; } /* - * send_byte - Write to SMC port, retrying when necessary. Callers + * send_byte_data - Write to SMC data port. Callers * must hold applesmc_lock. + * Parameter skip must be true on the last write of any + * command or it'll time out. */ -static int send_byte(u8 cmd, u16 port) + +static int send_byte_data(u8 cmd, u16 port, bool skip) { - u8 status; - int us; - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; + int ret; + ret = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY | SMC_STATUS_IB_CLOSED); + if (ret) + return ret; outb(cmd, port); - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - usleep_range(us, us * 16); - status = inb(APPLESMC_CMD_PORT); - /* write: wait for smc to settle */ - if (status & 0x02) - continue; - /* ready: cmd accepted, return */ - if (status & 0x04) - return 0; - /* timeout: give up */ - if (time_after(jiffies, end)) - break; - /* busy: long wait and resend */ - udelay(APPLESMC_RETRY_WAIT); - outb(cmd, port); - } + return wait_status(skip ? 0 : SMC_STATUS_BUSY, SMC_STATUS_BUSY); +} - pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status); - return -EIO; +static int send_byte(u8 cmd, u16 port) +{ + return send_byte_data(cmd, port, false); } +/* + * send_command - Write a command to the SMC. Callers must hold applesmc_lock. + * If SMC is in undefined state, any new command write resets the state machine. + */ + static int send_command(u8 cmd) { - return send_byte(cmd, APPLESMC_CMD_PORT); + u8 status; + int ret; + + ret = wait_status(0, SMC_STATUS_IB_CLOSED); + if (ret) + return ret; + + status = inb(APPLESMC_CMD_PORT); + + outb(cmd, APPLESMC_CMD_PORT); + return wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY); } static int send_argument(const char *key) @@ -239,7 +248,9 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) } for (i = 0; i < len; i++) { - if (wait_read()) { + if (wait_status(SMC_STATUS_AWAITING_DATA | SMC_STATUS_BUSY, + SMC_STATUS_AWAITING_DATA | SMC_STATUS_BUSY | + SMC_STATUS_IB_CLOSED)) { pr_warn("%.4s: read data[%d] fail\n", key, i); return -EIO; } @@ -250,7 +261,7 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) for (i = 0; i < 16; i++) { udelay(APPLESMC_MIN_WAIT); status = inb(APPLESMC_CMD_PORT); - if (!(status & 0x01)) + if (!(status & SMC_STATUS_AWAITING_DATA)) break; data = inb(APPLESMC_DATA_PORT); } @@ -275,7 +286,7 @@ static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len) } for (i = 0; i < len; i++) { - if (send_byte(buffer[i], APPLESMC_DATA_PORT)) { + if (send_byte_data(buffer[i], APPLESMC_DATA_PORT, i == len - 1)) { pr_warn("%s: write data fail\n", key); return -EIO; }