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[23.128.96.18]) by mx.google.com with ESMTP id m8si2488449edj.357.2020.11.05.16.06.44; Thu, 05 Nov 2020 16:07:09 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@fnarfbargle.com header.s=mail header.b=nZabsBfn; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=fnarfbargle.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732619AbgKFADq (ORCPT + 99 others); Thu, 5 Nov 2020 19:03:46 -0500 Received: from ns3.fnarfbargle.com ([103.4.19.87]:55424 "EHLO ns3.fnarfbargle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729784AbgKFADp (ORCPT ); Thu, 5 Nov 2020 19:03:45 -0500 Received: from srv.home ([10.8.0.1] ident=heh11857) by ns3.fnarfbargle.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1kapCc-0000gA-Iq; Fri, 06 Nov 2020 08:02:02 +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:From:References:Cc:To:Subject; bh=mrnTQlx4URaoQZqylMNRHrV1WLBTM2LXvxwuxfk7iBE=; b=nZabsBfnWrO6boX58eIQCS1Rl7kpr2TjCDMDq7y59O7S89dzXKX1YFhLHlKQpN697YdFzHWPo2++RgYLP0QkmewHd67/gmmktlF8PsrLyXcPrVRU/u3I0wQMutLbplzcrltGVoBTPMslLa1vS/vuO7uWeAEyIJBeQToH2CKQSic=; Subject: Re: [PATCH] applesmc: Re-work SMC comms v2 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, Henrik Rydberg 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> <3c72ccc3-4de1-b5d0-423d-7b8c80991254@fnarfbargle.com> From: Brad Campbell Message-ID: <34ff244b-fe98-fcf5-eb61-95a529a52c45@fnarfbargle.com> Date: Fri, 6 Nov 2020 11:02:00 +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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/11/20 3:12 am, Guenter Roeck wrote: > On 11/4/20 11:26 PM, Brad Campbell wrote: >> 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. >> > > Still a few formatting problems, but I like this version. Id take > care of the formatting myself, but send_command() will need a change. Nope, I'm more than happy to sort it all out. It's a learning process. I'd still like this to get some wider testing before I consider it ready to go so extra revisions don't worry me. > Subject should be > [PATCH v] hwmon: (applesmc) ... Thanks. >> v2 : Address logic and coding style > > Change log should be after '---' No worries, can do. > >> >> Reported-by: Andreas Kemnade >> Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") >> Signed-off-by: Brad Campbell >> >> --- >> 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 */ >> + > > Hah, tricked you here ;-). Using "BIT()" requires > > #include "requires" ?? It compiles and tests without warning, but I'll certainly add it in. >> /* 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); >> + } > > Bad indentation of "}" Yeah, I've found my editor "less than optimal" and I've had to correct a few tab related indent problems manually. Thanks. >> 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); >> + > > Is this read necessary ? 'status' isn't used subsequently, meaning we'll > probably get static analyzer warnings about a variable which is assigned > but unused. If the read is necessary, just don't assign it to a variable. No it's not. It's hangover from incompletely remove debug statements. Henrik Rydberg picked that one up yesterday. >> + 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; >> } >> > > I'll get a v3 in when I get some more test results. Much appreciated. Regards, Brad