Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753360AbdLGQ0z (ORCPT ); Thu, 7 Dec 2017 11:26:55 -0500 Received: from mail-oi0-f65.google.com ([209.85.218.65]:44419 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752577AbdLGQ0v (ORCPT ); Thu, 7 Dec 2017 11:26:51 -0500 X-Google-Smtp-Source: AGs4zMZ23wBSVBheTXfYbRfe84N21JXmEIWDmvtEZrDkLC403lF7rkzDQsDJIsOIYUB8pQHXLETxsq3udggSV1Gb8gQ= MIME-Version: 1.0 In-Reply-To: <1512657378-5221-2-git-send-email-svendev@arcx.com> References: <1512657378-5221-1-git-send-email-svendev@arcx.com> <1512657378-5221-2-git-send-email-svendev@arcx.com> From: Bartosz Golaszewski Date: Thu, 7 Dec 2017 17:26:50 +0100 Message-ID: Subject: Re: [PATCH v5 1/2] at24: support eeproms that do not auto-rollover reads. To: Sven Van Asbroeck Cc: Rob Herring , Mark Rutland , Wolfram Sang , nsekhar@ti.com, Sakari Ailus , David Lechner , Javier Martinez Canillas , Divagar Mohandass , devicetree@vger.kernel.org, Linux Kernel Mailing List , linux-i2c Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5026 Lines: 127 2017-12-07 15:36 GMT+01:00 Sven Van Asbroeck : > Some multi-address eeproms in the at24 family may not automatically > roll-over reads to the next slave address. On those eeproms, reads > that straddle slave boundaries will not work correctly. > > Solution: > Mark such eeproms with a flag that prevents reads straddling > slave boundaries. Add the AT24_FLAG_NO_RDROL flag to the eeprom > entry in the device_id table, or add 'no-read-rollover' to the > eeprom devicetree entry. > > Note that I have not personally enountered an at24 chip that > does not support read rollovers. They may or may not exist. > However, my hardware requires this functionality because of > a quirk. > > It's up to the Linux community to decide if this patch is useful/ > general enough to warrant merging. > > Signed-off-by: Sven Van Asbroeck > --- > drivers/misc/eeprom/at24.c | 37 +++++++++++++++++++++++++------------ > include/linux/platform_data/at24.h | 2 ++ > 2 files changed, 27 insertions(+), 12 deletions(-) > Hi Sven, looks good in general, just a couple nits to fix below and it can be applied. > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c > index 625b001..8c93ed0 100644 > --- a/drivers/misc/eeprom/at24.c > +++ b/drivers/misc/eeprom/at24.c > @@ -251,15 +251,6 @@ struct at24_data { > * Slave address and byte offset derive from the offset. Always > * set the byte address; on a multi-master board, another master > * may have changed the chip's "current" address pointer. > - * > - * REVISIT some multi-address chips don't rollover page reads to > - * the next slave address, so we may need to truncate the count. > - * Those chips might need another quirk flag. > - * > - * If the real hardware used four adjacent 24c02 chips and that > - * were misconfigured as one 24c08, that would be a similar effect: > - * one "eeprom" file not four, but larger reads would fail when > - * they crossed certain pages. > */ > static struct at24_client *at24_translate_offset(struct at24_data *at24, > unsigned int *offset) > @@ -277,6 +268,28 @@ static struct at24_client *at24_translate_offset(struct at24_data *at24, > return &at24->client[i]; > } > > +static size_t at24_adjust_read_count(struct at24_data *at24, > + unsigned int offset, size_t count) > +{ > + unsigned int bits; > + size_t remainder; Add a newline here. > + /* > + * In case of multi-address chips that don't rollover reads to > + * the next slave address: truncate the count to the slave boundary, > + * so that the read never straddles slaves. > + */ > + if (at24->chip.flags & AT24_FLAG_NO_RDROL) { > + bits = (at24->chip.flags & AT24_FLAG_ADDR16) ? 16 : 8; There's no need for braces around the ternary operator's condition. > + remainder = BIT(bits) - offset; > + if (count > remainder) > + count = remainder; > + } Another newline here. > + if (count > io_limit) > + count = io_limit; > + > + return count; > +} > + > static ssize_t at24_regmap_read(struct at24_data *at24, char *buf, > unsigned int offset, size_t count) > { > @@ -289,9 +302,7 @@ static ssize_t at24_regmap_read(struct at24_data *at24, char *buf, > at24_client = at24_translate_offset(at24, &offset); > regmap = at24_client->regmap; > client = at24_client->client; > - > - if (count > io_limit) > - count = io_limit; > + count = at24_adjust_read_count(at24, offset, count); > > /* adjust offset for mac and serial read ops */ > offset += at24->offset_adj; > @@ -457,6 +468,8 @@ static void at24_get_pdata(struct device *dev, struct at24_platform_data *chip) > > if (device_property_present(dev, "read-only")) > chip->flags |= AT24_FLAG_READONLY; > + if (device_property_present(dev, "no-read-rollover")) > + chip->flags |= AT24_FLAG_NO_RDROL; > > err = device_property_read_u32(dev, "size", &val); > if (!err) > diff --git a/include/linux/platform_data/at24.h b/include/linux/platform_data/at24.h > index 271a4e2..841bb28 100644 > --- a/include/linux/platform_data/at24.h > +++ b/include/linux/platform_data/at24.h > @@ -50,6 +50,8 @@ struct at24_platform_data { > #define AT24_FLAG_TAKE8ADDR BIT(4) /* take always 8 addresses (24c00) */ > #define AT24_FLAG_SERIAL BIT(3) /* factory-programmed serial number */ > #define AT24_FLAG_MAC BIT(2) /* factory-programmed mac address */ > +#define AT24_FLAG_NO_RDROL BIT(1) /* does not auto-rollover reads to */ > + /* the next slave address */ > > void (*setup)(struct nvmem_device *nvmem, void *context); > void *context; > -- > 1.9.1 > Thanks, Bartosz