From: Joel Stanley <joel@jms.id.au> To: Rob Herring <robh+dt@kernel.org>, Greg KH <gregkh@linuxfoundation.org>, Jeremy Kerr <jk@ozlabs.org> Cc: Andrew Jeffery <andrew@aj.id.au>, Alistar Popple <alistair@popple.id.au>, Eddie James <eajames@linux.ibm.com>, Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsi@lists.ozlabs.org Subject: [PATCH v2 05/11] fsi: core: Fix small accesses and unaligned offsets via sysfs Date: Fri, 8 Nov 2019 15:49:39 +1030 [thread overview] Message-ID: <20191108051945.7109-6-joel@jms.id.au> (raw) In-Reply-To: <20191108051945.7109-1-joel@jms.id.au> From: Andrew Jeffery <andrew@aj.id.au> Subtracting the offset delta from four-byte alignment lead to wrapping of the requested length where `count` is less than `off`. Generalise the length handling to enable and optimise aligned access sizes for all offset and size combinations. The new formula produces the following results for given offset and count values: offset count | length --------------+------- 0 1 | 1 0 2 | 2 0 3 | 2 0 4 | 4 0 5 | 4 1 1 | 1 1 2 | 1 1 3 | 1 1 4 | 1 1 5 | 1 2 1 | 1 2 2 | 2 2 3 | 2 2 4 | 2 2 5 | 2 3 1 | 1 3 2 | 1 3 3 | 1 3 4 | 1 3 5 | 1 We might need something like this for the cfam chardevs as well, for example we don't currently implement any alignment restrictions / handling in the hardware master driver. Signed-off-by: Andrew Jeffery <andrew@aj.id.au> Signed-off-by: Joel Stanley <joel@jms.id.au> --- drivers/fsi/fsi-core.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-) diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index c773c65a5058..e02ebcb0c9e6 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -544,6 +544,31 @@ static int fsi_slave_scan(struct fsi_slave *slave) return 0; } +static unsigned long aligned_access_size(size_t offset, size_t count) +{ + unsigned long offset_unit, count_unit; + + /* Criteria: + * + * 1. Access size must be less than or equal to the maximum access + * width or the highest power-of-two factor of offset + * 2. Access size must be less than or equal to the amount specified by + * count + * + * The access width is optimal if we can calculate 1 to be strictly + * equal while still satisfying 2. + */ + + /* Find 1 by the bottom bit of offset (with a 4 byte access cap) */ + offset_unit = BIT(__builtin_ctzl(offset | 4)); + + /* Find 2 by the top bit of count */ + count_unit = BIT(8 * sizeof(unsigned long) - 1 - __builtin_clzl(count)); + + /* Constrain the maximum access width to the minimum of both criteria */ + return BIT(__builtin_ctzl(offset_unit | count_unit)); +} + static ssize_t fsi_slave_sysfs_raw_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) @@ -559,8 +584,7 @@ static ssize_t fsi_slave_sysfs_raw_read(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += read_len) { - read_len = min_t(size_t, count, 4); - read_len -= off & 0x3; + read_len = aligned_access_size(off, count - total_len); rc = fsi_slave_read(slave, off, buf + total_len, read_len); if (rc) @@ -587,8 +611,7 @@ static ssize_t fsi_slave_sysfs_raw_write(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += write_len) { - write_len = min_t(size_t, count, 4); - write_len -= off & 0x3; + write_len = aligned_access_size(off, count - total_len); rc = fsi_slave_write(slave, off, buf + total_len, write_len); if (rc) -- 2.24.0.rc1
WARNING: multiple messages have this Message-ID (diff)
From: Joel Stanley <joel@jms.id.au> To: Rob Herring <robh+dt@kernel.org>, Greg KH <gregkh@linuxfoundation.org>, Jeremy Kerr <jk@ozlabs.org> Cc: devicetree@vger.kernel.org, Andrew Jeffery <andrew@aj.id.au>, Alistar Popple <alistair@popple.id.au>, Eddie James <eajames@linux.ibm.com>, linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>, linux-arm-kernel@lists.infradead.org, linux-fsi@lists.ozlabs.org Subject: [PATCH v2 05/11] fsi: core: Fix small accesses and unaligned offsets via sysfs Date: Fri, 8 Nov 2019 15:49:39 +1030 [thread overview] Message-ID: <20191108051945.7109-6-joel@jms.id.au> (raw) In-Reply-To: <20191108051945.7109-1-joel@jms.id.au> From: Andrew Jeffery <andrew@aj.id.au> Subtracting the offset delta from four-byte alignment lead to wrapping of the requested length where `count` is less than `off`. Generalise the length handling to enable and optimise aligned access sizes for all offset and size combinations. The new formula produces the following results for given offset and count values: offset count | length --------------+------- 0 1 | 1 0 2 | 2 0 3 | 2 0 4 | 4 0 5 | 4 1 1 | 1 1 2 | 1 1 3 | 1 1 4 | 1 1 5 | 1 2 1 | 1 2 2 | 2 2 3 | 2 2 4 | 2 2 5 | 2 3 1 | 1 3 2 | 1 3 3 | 1 3 4 | 1 3 5 | 1 We might need something like this for the cfam chardevs as well, for example we don't currently implement any alignment restrictions / handling in the hardware master driver. Signed-off-by: Andrew Jeffery <andrew@aj.id.au> Signed-off-by: Joel Stanley <joel@jms.id.au> --- drivers/fsi/fsi-core.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-) diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index c773c65a5058..e02ebcb0c9e6 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -544,6 +544,31 @@ static int fsi_slave_scan(struct fsi_slave *slave) return 0; } +static unsigned long aligned_access_size(size_t offset, size_t count) +{ + unsigned long offset_unit, count_unit; + + /* Criteria: + * + * 1. Access size must be less than or equal to the maximum access + * width or the highest power-of-two factor of offset + * 2. Access size must be less than or equal to the amount specified by + * count + * + * The access width is optimal if we can calculate 1 to be strictly + * equal while still satisfying 2. + */ + + /* Find 1 by the bottom bit of offset (with a 4 byte access cap) */ + offset_unit = BIT(__builtin_ctzl(offset | 4)); + + /* Find 2 by the top bit of count */ + count_unit = BIT(8 * sizeof(unsigned long) - 1 - __builtin_clzl(count)); + + /* Constrain the maximum access width to the minimum of both criteria */ + return BIT(__builtin_ctzl(offset_unit | count_unit)); +} + static ssize_t fsi_slave_sysfs_raw_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) @@ -559,8 +584,7 @@ static ssize_t fsi_slave_sysfs_raw_read(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += read_len) { - read_len = min_t(size_t, count, 4); - read_len -= off & 0x3; + read_len = aligned_access_size(off, count - total_len); rc = fsi_slave_read(slave, off, buf + total_len, read_len); if (rc) @@ -587,8 +611,7 @@ static ssize_t fsi_slave_sysfs_raw_write(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += write_len) { - write_len = min_t(size_t, count, 4); - write_len -= off & 0x3; + write_len = aligned_access_size(off, count - total_len); rc = fsi_slave_write(slave, off, buf + total_len, write_len); if (rc) -- 2.24.0.rc1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-11-08 5:20 UTC|newest] Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-11-08 5:19 [PATCH v2 00/11] fsi: Patches for 5.5 Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 5:19 ` [PATCH v2 01/11] fsi: Add fsi-master class Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:17 ` Alistair Popple 2019-11-08 9:17 ` Alistair Popple 2019-11-08 5:19 ` [PATCH v2 02/11] fsi: Move master attributes to " Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:18 ` Alistair Popple 2019-11-08 9:18 ` Alistair Popple 2019-11-08 5:19 ` [PATCH v2 03/11] ABI: Update FSI path documentation Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:27 ` Alistair Popple 2019-11-08 9:27 ` Alistair Popple 2019-11-08 5:19 ` [PATCH v2 04/11] trace: fsi: Print transfer size unsigned Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:21 ` Alistair Popple 2019-11-08 9:21 ` Alistair Popple 2019-11-08 5:19 ` Joel Stanley [this message] 2019-11-08 5:19 ` [PATCH v2 05/11] fsi: core: Fix small accesses and unaligned offsets via sysfs Joel Stanley 2019-11-08 5:19 ` [PATCH v2 06/11] fsi: fsi_master_class can be static Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 5:19 ` [PATCH v2 07/11] fsi: Move defines to common header Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 5:19 ` [PATCH v2 08/11] dt-bindings: fsi: Add description of FSI master Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:23 ` Alistair Popple 2019-11-08 9:23 ` Alistair Popple 2019-11-08 10:28 ` Greg KH 2019-11-08 10:28 ` Greg KH 2019-11-08 5:19 ` [PATCH v2 09/11] fsi: Add ast2600 master driver Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:29 ` Alistair Popple 2019-11-08 9:29 ` Alistair Popple 2019-11-08 5:19 ` [PATCH v2 10/11] fsi: aspeed: Add trace points Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 5:19 ` [PATCH v2 11/11] fsi: aspeed: Fix OPB0 byte order register values Joel Stanley 2019-11-08 5:19 ` Joel Stanley 2019-11-08 9:31 ` Alistair Popple 2019-11-08 9:31 ` Alistair Popple
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