Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753206AbbERKzV (ORCPT ); Mon, 18 May 2015 06:55:21 -0400 Received: from mga01.intel.com ([192.55.52.88]:7159 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858AbbERKzM convert rfc822-to-8bit (ORCPT ); Mon, 18 May 2015 06:55:12 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,453,1427785200"; d="scan'208";a="727690759" From: Jani Nikula To: Luis Henriques , Jiri Slaby Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Torokhov , Ben Hutchings Subject: Re: [PATCH 3.12 071/142] drm/i915: cope with large i2c transfers In-Reply-To: <20150518095602.GD1719@ares> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <378e22f618cf6c4274fd7b928fd7b10ec380c6f6.1431761807.git.jslaby@suse.cz> <20150518095602.GD1719@ares> User-Agent: Notmuch/0.19+112~g77230b0 (http://notmuchmail.org) Emacs/24.4.1 (x86_64-pc-linux-gnu) Date: Mon, 18 May 2015 13:57:20 +0300 Message-ID: <87a8x22lwv.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6403 Lines: 199 On Mon, 18 May 2015, Luis Henriques wrote: > On Sat, May 16, 2015 at 09:37:11AM +0200, Jiri Slaby wrote: >> From: Dmitry Torokhov >> >> 3.12-stable review patch. If anyone has any objections, please let me know. >> > > Ben Hutchings (on CC) just asked about this patch being included on > the 3.16 kernel [1]. Is this patch really useful for kernels < 3.17? > Should it be reverted from all the other stable kernels (3.10, 3.14 > and 3.16), or do you think it's harmless? The bug fixed by Dmitry's patch has been there since the introduction of the gmbus code in v2.6.37 by commit f899fc64cda8569d0529452aafc0da31c042df2e Author: Chris Wilson Date: Tue Jul 20 15:44:45 2010 -0700 drm/i915: use GMBUS to manage i2c links It's just that nobody noticed before commit 9d8dc3e529a19e427fd379118acd132520935c5d Author: Nick Dyer Date: Wed Jul 23 12:49:04 2014 -0700 Input: atmel_mxt_ts - implement T44 message handling BR, Jani. > > [1] http://thread.gmane.org/gmane.linux.kernel.stable/136673 > > Cheers, > -- > Luís > >> =============== >> >> commit 9535c4757b881e06fae72a857485ad57c422b8d2 upstream. >> >> The hardware, according to the specs, is limited to 256 byte transfers, >> and current driver has no protections in case users attempt to do larger >> transfers. The code will just stomp over status register and mayhem >> ensues. >> >> Let's split larger transfers into digestable chunks. Doing this allows >> Atmel MXT driver on Pixel 1 function properly (it hasn't since commit >> 9d8dc3e529a19e427fd379118acd132520935c5d "Input: atmel_mxt_ts - >> implement T44 message handling" which tries to consume multiple >> touchscreen/touchpad reports in a single transaction). >> >> Reviewed-by: Chris Wilson >> Signed-off-by: Dmitry Torokhov >> Signed-off-by: Jani Nikula >> Signed-off-by: Jiri Slaby >> --- >> drivers/gpu/drm/i915/i915_reg.h | 1 + >> drivers/gpu/drm/i915/intel_i2c.c | 66 ++++++++++++++++++++++++++++++++++------ >> 2 files changed, 57 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h >> index 9d344da55056..4e0053e64f14 100644 >> --- a/drivers/gpu/drm/i915/i915_reg.h >> +++ b/drivers/gpu/drm/i915/i915_reg.h >> @@ -1105,6 +1105,7 @@ >> #define GMBUS_CYCLE_INDEX (2<<25) >> #define GMBUS_CYCLE_STOP (4<<25) >> #define GMBUS_BYTE_COUNT_SHIFT 16 >> +#define GMBUS_BYTE_COUNT_MAX 256U >> #define GMBUS_SLAVE_INDEX_SHIFT 8 >> #define GMBUS_SLAVE_ADDR_SHIFT 1 >> #define GMBUS_SLAVE_READ (1<<0) >> diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c >> index d1c1e0f7f262..36b720475dc0 100644 >> --- a/drivers/gpu/drm/i915/intel_i2c.c >> +++ b/drivers/gpu/drm/i915/intel_i2c.c >> @@ -276,18 +276,17 @@ gmbus_wait_idle(struct drm_i915_private *dev_priv) >> } >> >> static int >> -gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, >> - u32 gmbus1_index) >> +gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv, >> + unsigned short addr, u8 *buf, unsigned int len, >> + u32 gmbus1_index) >> { >> int reg_offset = dev_priv->gpio_mmio_base; >> - u16 len = msg->len; >> - u8 *buf = msg->buf; >> >> I915_WRITE(GMBUS1 + reg_offset, >> gmbus1_index | >> GMBUS_CYCLE_WAIT | >> (len << GMBUS_BYTE_COUNT_SHIFT) | >> - (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) | >> + (addr << GMBUS_SLAVE_ADDR_SHIFT) | >> GMBUS_SLAVE_READ | GMBUS_SW_RDY); >> while (len) { >> int ret; >> @@ -309,11 +308,35 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, >> } >> >> static int >> -gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >> +gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, >> + u32 gmbus1_index) >> { >> - int reg_offset = dev_priv->gpio_mmio_base; >> - u16 len = msg->len; >> u8 *buf = msg->buf; >> + unsigned int rx_size = msg->len; >> + unsigned int len; >> + int ret; >> + >> + do { >> + len = min(rx_size, GMBUS_BYTE_COUNT_MAX); >> + >> + ret = gmbus_xfer_read_chunk(dev_priv, msg->addr, >> + buf, len, gmbus1_index); >> + if (ret) >> + return ret; >> + >> + rx_size -= len; >> + buf += len; >> + } while (rx_size != 0); >> + >> + return 0; >> +} >> + >> +static int >> +gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv, >> + unsigned short addr, u8 *buf, unsigned int len) >> +{ >> + int reg_offset = dev_priv->gpio_mmio_base; >> + unsigned int chunk_size = len; >> u32 val, loop; >> >> val = loop = 0; >> @@ -325,8 +348,8 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >> I915_WRITE(GMBUS3 + reg_offset, val); >> I915_WRITE(GMBUS1 + reg_offset, >> GMBUS_CYCLE_WAIT | >> - (msg->len << GMBUS_BYTE_COUNT_SHIFT) | >> - (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) | >> + (chunk_size << GMBUS_BYTE_COUNT_SHIFT) | >> + (addr << GMBUS_SLAVE_ADDR_SHIFT) | >> GMBUS_SLAVE_WRITE | GMBUS_SW_RDY); >> while (len) { >> int ret; >> @@ -343,6 +366,29 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >> if (ret) >> return ret; >> } >> + >> + return 0; >> +} >> + >> +static int >> +gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >> +{ >> + u8 *buf = msg->buf; >> + unsigned int tx_size = msg->len; >> + unsigned int len; >> + int ret; >> + >> + do { >> + len = min(tx_size, GMBUS_BYTE_COUNT_MAX); >> + >> + ret = gmbus_xfer_write_chunk(dev_priv, msg->addr, buf, len); >> + if (ret) >> + return ret; >> + >> + buf += len; >> + tx_size -= len; >> + } while (tx_size != 0); >> + >> return 0; >> } >> >> -- >> 2.3.7 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe stable" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jani Nikula, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/