linux/drivers/gpu/drm/drm_dp_dual_mode_helper.c
Michal Hocko 0ee931c4e3 mm: treewide: remove GFP_TEMPORARY allocation flag
GFP_TEMPORARY was introduced by commit e12ba74d8f ("Group short-lived
and reclaimable kernel allocations") along with __GFP_RECLAIMABLE.  It's
primary motivation was to allow users to tell that an allocation is
short lived and so the allocator can try to place such allocations close
together and prevent long term fragmentation.  As much as this sounds
like a reasonable semantic it becomes much less clear when to use the
highlevel GFP_TEMPORARY allocation flag.  How long is temporary? Can the
context holding that memory sleep? Can it take locks? It seems there is
no good answer for those questions.

The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
__GFP_RECLAIMABLE which in itself is tricky because basically none of
the existing caller provide a way to reclaim the allocated memory.  So
this is rather misleading and hard to evaluate for any benefits.

I have checked some random users and none of them has added the flag
with a specific justification.  I suspect most of them just copied from
other existing users and others just thought it might be a good idea to
use without any measuring.  This suggests that GFP_TEMPORARY just
motivates for cargo cult usage without any reasoning.

I believe that our gfp flags are quite complex already and especially
those with highlevel semantic should be clearly defined to prevent from
confusion and abuse.  Therefore I propose dropping GFP_TEMPORARY and
replace all existing users to simply use GFP_KERNEL.  Please note that
SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
so they will be placed properly for memory fragmentation prevention.

I can see reasons we might want some gfp flag to reflect shorterm
allocations but I propose starting from a clear semantic definition and
only then add users with proper justification.

This was been brought up before LSF this year by Matthew [1] and it
turned out that GFP_TEMPORARY really doesn't have a clear semantic.  It
seems to be a heuristic without any measured advantage for most (if not
all) its current users.  The follow up discussion has revealed that
opinions on what might be temporary allocation differ a lot between
developers.  So rather than trying to tweak existing users into a
semantic which they haven't expected I propose to simply remove the flag
and start from scratch if we really need a semantic for short term
allocations.

[1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org

[akpm@linux-foundation.org: fix typo]
[akpm@linux-foundation.org: coding-style fixes]
[sfr@canb.auug.org.au: drm/i915: fix up]
  Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-13 18:53:16 -07:00

490 lines
14 KiB
C

/*
* Copyright © 2016 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <drm/drm_dp_dual_mode_helper.h>
#include <drm/drmP.h>
/**
* DOC: dp dual mode helpers
*
* Helper functions to deal with DP dual mode (aka. DP++) adaptors.
*
* Type 1:
* Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
*
* Type 2:
* Adaptor registers and sink DDC bus can be accessed either via I2C or
* I2C-over-AUX. Source devices may choose to implement either of these
* access methods.
*/
#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40
/**
* drm_dp_dual_mode_read - Read from the DP dual mode adaptor register(s)
* @adapter: I2C adapter for the DDC bus
* @offset: register offset
* @buffer: buffer for return data
* @size: sizo of the buffer
*
* Reads @size bytes from the DP dual mode adaptor registers
* starting at @offset.
*
* Returns:
* 0 on success, negative error code on failure
*/
ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
u8 offset, void *buffer, size_t size)
{
struct i2c_msg msgs[] = {
{
.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
.flags = 0,
.len = 1,
.buf = &offset,
},
{
.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
.flags = I2C_M_RD,
.len = size,
.buf = buffer,
},
};
int ret;
ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
if (ret < 0)
return ret;
if (ret != ARRAY_SIZE(msgs))
return -EPROTO;
return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_read);
/**
* drm_dp_dual_mode_write - Write to the DP dual mode adaptor register(s)
* @adapter: I2C adapter for the DDC bus
* @offset: register offset
* @buffer: buffer for write data
* @size: sizo of the buffer
*
* Writes @size bytes to the DP dual mode adaptor registers
* starting at @offset.
*
* Returns:
* 0 on success, negative error code on failure
*/
ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
u8 offset, const void *buffer, size_t size)
{
struct i2c_msg msg = {
.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
.flags = 0,
.len = 1 + size,
.buf = NULL,
};
void *data;
int ret;
data = kmalloc(msg.len, GFP_KERNEL);
if (!data)
return -ENOMEM;
msg.buf = data;
memcpy(data, &offset, 1);
memcpy(data + 1, buffer, size);
ret = i2c_transfer(adapter, &msg, 1);
kfree(data);
if (ret < 0)
return ret;
if (ret != 1)
return -EPROTO;
return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_write);
static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
{
static const char dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
"DP-HDMI ADAPTOR\x04";
return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
sizeof(dp_dual_mode_hdmi_id)) == 0;
}
static bool is_type1_adaptor(uint8_t adaptor_id)
{
return adaptor_id == 0 || adaptor_id == 0xff;
}
static bool is_type2_adaptor(uint8_t adaptor_id)
{
return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
DP_DUAL_MODE_REV_TYPE2);
}
static bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
const uint8_t adaptor_id)
{
return is_hdmi_adaptor(hdmi_id) &&
(adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
DP_DUAL_MODE_TYPE_HAS_DPCD));
}
/**
* drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
* @adapter: I2C adapter for the DDC bus
*
* Attempt to identify the type of the DP dual mode adaptor used.
*
* Note that when the answer is @DRM_DP_DUAL_MODE_UNKNOWN it's not
* certain whether we're dealing with a native HDMI port or
* a type 1 DVI dual mode adaptor. The driver will have to use
* some other hardware/driver specific mechanism to make that
* distinction.
*
* Returns:
* The type of the DP dual mode adaptor used
*/
enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
{
char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
uint8_t adaptor_id = 0x00;
ssize_t ret;
/*
* Let's see if the adaptor is there the by reading the
* HDMI ID registers.
*
* Note that type 1 DVI adaptors are not required to implemnt
* any registers, and that presents a problem for detection.
* If the i2c transfer is nacked, we may or may not be dealing
* with a type 1 DVI adaptor. Some other mechanism of detecting
* the presence of the adaptor is required. One way would be
* to check the state of the CONFIG1 pin, Another method would
* simply require the driver to know whether the port is a DP++
* port or a native HDMI port. Both of these methods are entirely
* hardware/driver specific so we can't deal with them here.
*/
ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
hdmi_id, sizeof(hdmi_id));
DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
if (ret)
return DRM_DP_DUAL_MODE_UNKNOWN;
/*
* Sigh. Some (maybe all?) type 1 adaptors are broken and ack
* the offset but ignore it, and instead they just always return
* data from the start of the HDMI ID buffer. So for a broken
* type 1 HDMI adaptor a single byte read will always give us
* 0x44, and for a type 1 DVI adaptor it should give 0x00
* (assuming it implements any registers). Fortunately neither
* of those values will match the type 2 signature of the
* DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
* the type 2 adaptor detection safely even in the presence
* of broken type 1 adaptors.
*/
ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
&adaptor_id, sizeof(adaptor_id));
DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
adaptor_id, ret);
if (ret == 0) {
if (is_lspcon_adaptor(hdmi_id, adaptor_id))
return DRM_DP_DUAL_MODE_LSPCON;
if (is_type2_adaptor(adaptor_id)) {
if (is_hdmi_adaptor(hdmi_id))
return DRM_DP_DUAL_MODE_TYPE2_HDMI;
else
return DRM_DP_DUAL_MODE_TYPE2_DVI;
}
/*
* If neither a proper type 1 ID nor a broken type 1 adaptor
* as described above, assume type 1, but let the user know
* that we may have misdetected the type.
*/
if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
DRM_ERROR("Unexpected DP dual mode adaptor ID %02x\n",
adaptor_id);
}
if (is_hdmi_adaptor(hdmi_id))
return DRM_DP_DUAL_MODE_TYPE1_HDMI;
else
return DRM_DP_DUAL_MODE_TYPE1_DVI;
}
EXPORT_SYMBOL(drm_dp_dual_mode_detect);
/**
* drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode adaptor
* @type: DP dual mode adaptor type
* @adapter: I2C adapter for the DDC bus
*
* Determine the max TMDS clock the adaptor supports based on the
* type of the dual mode adaptor and the DP_DUAL_MODE_MAX_TMDS_CLOCK
* register (on type2 adaptors). As some type 1 adaptors have
* problems with registers (see comments in drm_dp_dual_mode_detect())
* we don't read the register on those, instead we simply assume
* a 165 MHz limit based on the specification.
*
* Returns:
* Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
*/
int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
struct i2c_adapter *adapter)
{
uint8_t max_tmds_clock;
ssize_t ret;
/* native HDMI so no limit */
if (type == DRM_DP_DUAL_MODE_NONE)
return 0;
/*
* Type 1 adaptors are limited to 165MHz
* Type 2 adaptors can tells us their limit
*/
if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
return 165000;
ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_MAX_TMDS_CLOCK,
&max_tmds_clock, sizeof(max_tmds_clock));
if (ret || max_tmds_clock == 0x00 || max_tmds_clock == 0xff) {
DRM_DEBUG_KMS("Failed to query max TMDS clock\n");
return 165000;
}
return max_tmds_clock * 5000 / 2;
}
EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);
/**
* drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS output buffers in the DP dual mode adaptor
* @type: DP dual mode adaptor type
* @adapter: I2C adapter for the DDC bus
* @enabled: current state of the TMDS output buffers
*
* Get the state of the TMDS output buffers in the adaptor. For
* type2 adaptors this is queried from the DP_DUAL_MODE_TMDS_OEN
* register. As some type 1 adaptors have problems with registers
* (see comments in drm_dp_dual_mode_detect()) we don't read the
* register on those, instead we simply assume that the buffers
* are always enabled.
*
* Returns:
* 0 on success, negative error code on failure
*/
int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
struct i2c_adapter *adapter,
bool *enabled)
{
uint8_t tmds_oen;
ssize_t ret;
if (type < DRM_DP_DUAL_MODE_TYPE2_DVI) {
*enabled = true;
return 0;
}
ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
&tmds_oen, sizeof(tmds_oen));
if (ret) {
DRM_DEBUG_KMS("Failed to query state of TMDS output buffers\n");
return ret;
}
*enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);
return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);
/**
* drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output buffers in the DP dual mode adaptor
* @type: DP dual mode adaptor type
* @adapter: I2C adapter for the DDC bus
* @enable: enable (as opposed to disable) the TMDS output buffers
*
* Set the state of the TMDS output buffers in the adaptor. For
* type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
* some type 1 adaptors have problems with registers (see comments
* in drm_dp_dual_mode_detect()) we avoid touching the register,
* making this function a no-op on type 1 adaptors.
*
* Returns:
* 0 on success, negative error code on failure
*/
int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
struct i2c_adapter *adapter, bool enable)
{
uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
ssize_t ret;
if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
return 0;
ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
&tmds_oen, sizeof(tmds_oen));
if (ret) {
DRM_DEBUG_KMS("Failed to %s TMDS output buffers\n",
enable ? "enable" : "disable");
return ret;
}
return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);
/**
* drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode adaptor type as a string
* @type: DP dual mode adaptor type
*
* Returns:
* String representation of the DP dual mode adaptor type
*/
const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
{
switch (type) {
case DRM_DP_DUAL_MODE_NONE:
return "none";
case DRM_DP_DUAL_MODE_TYPE1_DVI:
return "type 1 DVI";
case DRM_DP_DUAL_MODE_TYPE1_HDMI:
return "type 1 HDMI";
case DRM_DP_DUAL_MODE_TYPE2_DVI:
return "type 2 DVI";
case DRM_DP_DUAL_MODE_TYPE2_HDMI:
return "type 2 HDMI";
case DRM_DP_DUAL_MODE_LSPCON:
return "lspcon";
default:
WARN_ON(type != DRM_DP_DUAL_MODE_UNKNOWN);
return "unknown";
}
}
EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
/**
* drm_lspcon_get_mode: Get LSPCON's current mode of operation by
* reading offset (0x80, 0x41)
* @adapter: I2C-over-aux adapter
* @mode: current lspcon mode of operation output variable
*
* Returns:
* 0 on success, sets the current_mode value to appropriate mode
* -error on failure
*/
int drm_lspcon_get_mode(struct i2c_adapter *adapter,
enum drm_lspcon_mode *mode)
{
u8 data;
int ret = 0;
if (!mode) {
DRM_ERROR("NULL input\n");
return -EINVAL;
}
/* Read Status: i2c over aux */
ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
&data, sizeof(data));
if (ret < 0) {
DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
return -EFAULT;
}
if (data & DP_DUAL_MODE_LSPCON_MODE_PCON)
*mode = DRM_LSPCON_MODE_PCON;
else
*mode = DRM_LSPCON_MODE_LS;
return 0;
}
EXPORT_SYMBOL(drm_lspcon_get_mode);
/**
* drm_lspcon_set_mode: Change LSPCON's mode of operation by
* writing offset (0x80, 0x40)
* @adapter: I2C-over-aux adapter
* @mode: required mode of operation
*
* Returns:
* 0 on success, -error on failure/timeout
*/
int drm_lspcon_set_mode(struct i2c_adapter *adapter,
enum drm_lspcon_mode mode)
{
u8 data = 0;
int ret;
int time_out = 200;
enum drm_lspcon_mode current_mode;
if (mode == DRM_LSPCON_MODE_PCON)
data = DP_DUAL_MODE_LSPCON_MODE_PCON;
/* Change mode */
ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
&data, sizeof(data));
if (ret < 0) {
DRM_ERROR("LSPCON mode change failed\n");
return ret;
}
/*
* Confirm mode change by reading the status bit.
* Sometimes, it takes a while to change the mode,
* so wait and retry until time out or done.
*/
do {
ret = drm_lspcon_get_mode(adapter, &current_mode);
if (ret) {
DRM_ERROR("can't confirm LSPCON mode change\n");
return ret;
} else {
if (current_mode != mode) {
msleep(10);
time_out -= 10;
} else {
DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
mode == DRM_LSPCON_MODE_LS ?
"LS" : "PCON");
return 0;
}
}
} while (time_out);
DRM_ERROR("LSPCON mode change timed out\n");
return -ETIMEDOUT;
}
EXPORT_SYMBOL(drm_lspcon_set_mode);