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drm/i915: cope with large i2c transfers

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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
9d8dc3e529 "Input: atmel_mxt_ts -
implement T44 message handling" which tries to consume multiple
touchscreen/touchpad reports in a single transaction).

Cc: stable@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
This commit is contained in:
Dmitry Torokhov 2015-04-21 09:49:11 -07:00 committed by Jani Nikula
parent 37ef01ab5d
commit 9535c4757b
2 changed files with 57 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/gpu/drm/i915/i915_reg.h
View File

@ -1807,6 +1807,7 @@ enum skl_disp_power_wells {
#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)

66
drivers/gpu/drm/i915/intel_i2c.c
View File

@ -270,18 +270,17 @@ 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;
@ -303,11 +302,35 @@ 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)
{
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;
u16 len = msg->len;
u8 *buf = msg->buf;
unsigned int chunk_size = len;
u32 val, loop;
val = loop = 0;
@ -319,8 +342,8 @@ 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;
@ -337,6 +360,29 @@ 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;
}