From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:14077 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933018Ab3CRVWM convert rfc822-to-8bit (ORCPT ); Mon, 18 Mar 2013 17:22:12 -0400 Date: Mon, 18 Mar 2013 18:22:05 -0300 From: Mauro Carvalho Chehab To: Frank =?UTF-8?B?U2Now6RmZXI=?= Cc: Devin Heitmueller , Linux Media Mailing List Subject: Re: [PATCH 0/3] em28xx: add support for two buses on em2874 and upper Message-ID: <20130318182205.44f44e20@redhat.com> In-Reply-To: <51378067.3000506@googlemail.com> References: <1362480928-20382-1-git-send-email-mchehab@redhat.com> <51378067.3000506@googlemail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-media-owner@vger.kernel.org List-ID: Em Wed, 06 Mar 2013 18:44:07 +0100 Frank Schäfer escreveu: > Am 05.03.2013 16:43, schrieb Devin Heitmueller: > > 2013/3/5 Mauro Carvalho Chehab : > >> The em2874 chips and upper have 2 buses. On all known devices, bus 0 is > >> currently used only by eeprom, and bus 1 for the rest. Add support to > >> register both buses. > > Did you add a mutex to ensure that both buses cannot be used at the > > same time? Because using the bus requires you to toggle a register > > (thus you cannot be using both busses at the same time), you cannot > > rely on the existing i2c adapter lock anymore. > > > > You don't want a situation where something is actively talking on bus > > 0, and then something else tries to talk on bus 1, flips the register > > bit and then the thread talking on bus 0 starts failing. > > > > Devin > > Hmm... there are several writes to EM28XX_R06_I2C_CLK in em28xx-dvb... > See hauppauge_hvr930c_init(), terratec_h5_init() and > terratec_htc_stick_init(). > These functions are called from em28xx_dvb_init() at module init. > Module init is async, so yes, this is (or could at least become) a > problem... > > I wonder if we can't simply remove all those writes to > EM28XX_R06_I2C_CLK from em28xx-dvb. > This is what the functions are doing: > > hauppauge_hvr930c_init() > ... > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x40); > msleep(10); > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x44); > msleep(10); > ... [init sequence for slave at address 0x82] > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x44); > msleep(30); > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x45); > msleep(10); > > terratec_h5_init(): > ... > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x40); > msleep(10); > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x45); > msleep(10); > ... > > terratec_htc_stick_init() > ... > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x40); > msleep(10); > em28xx_write_reg(dev, EM28XX_R06_I2C_CLK, 0x44); > msleep(10); > ... > > All three boards are using the following settings: > .i2c_speed = EM2874_I2C_SECONDARY_BUS_SELECT | > EM28XX_I2C_CLK_WAIT_ENABLE | EM28XX_I2C_FREQ_400_KHZ = 0x45 > > So what these functions are doing is > - switch to bus A and do nothing fo 10ms > - overwrite board settings for reg 0x06 with a local value (clears > EM28XX_I2C_FREQ_400_KHZ permanently for the HTC-Stick !). > > I can test the HVR-930C next week. There are some things there on the init sequence that can be cleaned/removed. Those sequences generally comes from observing what the original driver does. While it produces a working driver, in general, it is not optimized and part of the init sequence can be removed. Regards, Mauro