From patchwork Thu Nov 12 03:08:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brad Campbell X-Patchwork-Id: 11899007 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 3D3D21391 for ; Thu, 12 Nov 2020 05:39:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0533521D7F for ; Thu, 12 Nov 2020 05:39:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fnarfbargle.com header.i=@fnarfbargle.com header.b="dYWKyGgJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728030AbgKLFjL (ORCPT ); Thu, 12 Nov 2020 00:39:11 -0500 Received: from ns3.fnarfbargle.com ([103.4.19.87]:53710 "EHLO ns3.fnarfbargle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728063AbgKLDJ0 (ORCPT ); Wed, 11 Nov 2020 22:09:26 -0500 Received: from srv.home ([10.8.0.1] ident=heh16335) by ns3.fnarfbargle.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1kd2yH-0005EB-49; Thu, 12 Nov 2020 11:08:25 +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=yDWpF+/PotmPSr63teCZVZBkYUVOg1oSDJoZUN3M188=; b=dYWKyGgJ5cIgH00dwL9JxKBWFu7WbRizvXNjkucRtTv62GPeclcCYOji2p+HY99o6U3/0WWos32dfnGfFv0VcyxX/3Xc8O+l6RttIce2FdZEJxyhVd+yUARAu7JynLnN1rIaoeJgDwZ8y+H0dmoC2W+CnAFRxt8jKYv3C/HQtLk=; Subject: [PATCH v6 1/1] applesmc: Re-work SMC comms From: Brad Campbell To: linux-hwmon@vger.kernel.org Cc: Arnd Bergmann , "linux-kernel@vger.kernel.org" , hns@goldelico.com, Andreas Kemnade , Jean Delvare , Henrik Rydberg , Guenter Roeck References: <20200930105442.3f642f6c@aktux> <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> <3c72ccc3-4de1-b5d0-423d-7b8c80991254@fnarfbargle.com> <6d071547-10ee-ca92-ec8b-4b5069d04501@bitmath.org> <8e117844-d62a-bcb1-398d-c59cc0d4b878@fnarfbargle.com> <9109d059-d9cb-7464-edba-3f42aa78ce92@bitmath.org> <5310c0ab-0f80-1f9e-8807-066223edae13@bitmath.org> <57057d07-d3a0-8713-8365-7b12ca222bae@fnarfbargle.com> <4eca09dc-7b32-767c-eab0-b9ad8b41efcc@fnarfbargle.com> <8c525b3b-b4a6-8ee4-8128-a20e0ad408e4@fnarfbargle.com> Message-ID: <194a7d71-a781-765a-d177-c962ef296b90@fnarfbargle.com> Date: Thu, 12 Nov 2020 14:08:23 +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: <8c525b3b-b4a6-8ee4-8128-a20e0ad408e4@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. Tested on : MacbookAir6,2 MacBookPro11,1 iMac12,2, MacBookAir1,1, MacBookAir3,1 Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") Reported-by: Andreas Kemnade Tested-by: Andreas Kemnade # MacBookAir6,2 Acked-by: Arnd Bergmann Signed-off-by: Brad Campbell Signed-off-by: Henrik Rydberg --- Changelog : v1 : Initial attempt v2 : Address logic and coding style based on comments received v3 : Removed some debug hangover. Added tested-by. Modifications for MacBookAir1,1 - Significant rework of wait logic by Henrik Rydberg to make it function at all on the MacBookAir1,1. v4 : Re-factored logic based on Apple driver. Simplified wait_status loop - Re-factored the logic again, this time based on the Apple driver. This functioned without error on all tested Macs. wait_status() contributed by Henrik Rydberg v5 : Re-wrote status loop. Simplified busy check in send_byte() - Re-wrote wait_status() based on feedback from Guenter Roeck - Added additional comments to explain multiple tests in send_byte() - Addressed repeated indentation issues v6 : Reverted simplification of busy check in send_byte() - The logic simplification in v5 send_byte() caused a few read failures in stress testing on a fast SMC (3 in 5.6million). Reverting that change passed 5 million reads with 0 errors. Index: linux-stable/drivers/hwmon/applesmc.c =================================================================== --- linux-stable.orig/drivers/hwmon/applesmc.c +++ linux-stable/drivers/hwmon/applesmc.c @@ -32,6 +32,7 @@ #include #include #include +#include /* data port used by Apple SMC */ #define APPLESMC_DATA_PORT 0x300 @@ -42,10 +43,13 @@ #define APPLESMC_MAX_DATA_LENGTH 32 -/* wait up to 128 ms for a status change. */ -#define APPLESMC_MIN_WAIT 0x0010 -#define APPLESMC_RETRY_WAIT 0x0100 -#define APPLESMC_MAX_WAIT 0x20000 +/* Apple SMC status bits */ +#define SMC_STATUS_AWAITING_DATA BIT(0) /* SMC has data waiting to be read */ +#define SMC_STATUS_IB_CLOSED BIT(1) /* Will ignore any input */ +#define SMC_STATUS_BUSY BIT(2) /* Command in progress */ + +/* Initial wait is 8us */ +#define APPLESMC_MIN_WAIT 0x0008 #define APPLESMC_READ_CMD 0x10 #define APPLESMC_WRITE_CMD 0x11 @@ -151,65 +155,84 @@ 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 all transactions. + * This does 10 fast loops of 8us then exponentially backs off for a + * minimum total wait of 262ms. Depending on usleep_range this could + * run out past 500ms. */ -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; + int i; - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - usleep_range(us, us * 16); + us = APPLESMC_MIN_WAIT; + for (i = 0; i < 24 ; i++) { 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; + usleep_range(us, us * 2); + if (i > 9) + us <<= 1; } - - pr_warn("wait_read() fail: 0x%02x\n", status); return -EIO; } -/* - * send_byte - Write to SMC port, retrying when necessary. Callers - * must hold applesmc_lock. - */ +/* send_byte - Write to SMC data port. Callers must hold applesmc_lock. */ + static int send_byte(u8 cmd, u16 port) { - u8 status; - int us; - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; + int status; - 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); - } + status = wait_status(0, SMC_STATUS_IB_CLOSED); + if (status) + return status; + /* + * This needs to be a separate read looking for bit 0x04 + * after bit 0x02 falls. If consolidated with the wait above + * this extra read may not happen if status returns both + * simultaneously and this would appear to be required. + */ + status = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY); + if (status) + return status; - pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status); - return -EIO; + outb(cmd, port); + return 0; } +/* send_command - Write a command to the SMC. Callers must hold applesmc_lock. */ + static int send_command(u8 cmd) { - return send_byte(cmd, APPLESMC_CMD_PORT); + int ret; + + ret = wait_status(0, SMC_STATUS_IB_CLOSED); + if (ret) + return ret; + outb(cmd, APPLESMC_CMD_PORT); + return 0; +} + +/* + * Based on logic from the Apple driver. This is issued before any interaction + * If busy is stuck high, issue a read command to reset the SMC state machine. + * If busy is stuck high after the command then the SMC is jammed. + */ + +static int smc_sane(void) +{ + int ret; + + ret = wait_status(0, SMC_STATUS_BUSY); + if (!ret) + return ret; + ret = send_command(APPLESMC_READ_CMD); + if (ret) + return ret; + return wait_status(0, SMC_STATUS_BUSY); } static int send_argument(const char *key) @@ -226,6 +249,11 @@ static int read_smc(u8 cmd, const char * { u8 status, data = 0; int i; + int ret; + + ret = smc_sane(); + if (ret) + return ret; if (send_command(cmd) || send_argument(key)) { pr_warn("%.4s: read arg fail\n", key); @@ -239,7 +267,8 @@ static int read_smc(u8 cmd, const char * } 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)) { pr_warn("%.4s: read data[%d] fail\n", key, i); return -EIO; } @@ -250,19 +279,24 @@ static int read_smc(u8 cmd, const char * 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); } if (i) pr_warn("flushed %d bytes, last value is: %d\n", i, data); - return 0; + return wait_status(0, SMC_STATUS_BUSY); } static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len) { int i; + int ret; + + ret = smc_sane(); + if (ret) + return ret; if (send_command(cmd) || send_argument(key)) { pr_warn("%s: write arg fail\n", key); @@ -281,7 +315,7 @@ static int write_smc(u8 cmd, const char } } - return 0; + return wait_status(0, SMC_STATUS_BUSY); } static int read_register_count(unsigned int *count)