* When reading from the EEPROM device, there is no
device limitation on the number of bytes
read--they're simply sequenced out. Thus, read
the whole data requested in one go.
* When writing to the EEPROM device, there is a
256-byte page limit to write to before having to
generate a STOP on the bus, as well as the
address written to mustn't cross over the page
boundary (it actually rolls over). Maximize the
data written to per bus acquisition.
* Return the number of bytes read/written, or -errno.
* Add kernel doc.
Cc: Jean Delvare <jdelvare@xxxxxxx>
Cc: Alexander Deucher <Alexander.Deucher@xxxxxxx>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@xxxxxxx>
Cc: Lijo Lazar <Lijo.Lazar@xxxxxxx>
Cc: Stanley Yang <Stanley.Yang@xxxxxxx>
Cc: Hawking Zhang <Hawking.Zhang@xxxxxxx>
Signed-off-by: Luben Tuikov <luben.tuikov@xxxxxxx>
Acked-by: Alexander Deucher <Alexander.Deucher@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c | 96 +++++++++++++++-------
1 file changed, 68 insertions(+), 28 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c
index d02ea083a6c69b..7fdb5bd2fc8bc8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c
@@ -24,59 +24,99 @@
#include "amdgpu_eeprom.h"
#include "amdgpu.h"
-#define EEPROM_OFFSET_LENGTH 2
+/* AT24CM02 has a 256-byte write page size.
+ */
+#define EEPROM_PAGE_BITS 8
+#define EEPROM_PAGE_SIZE (1U << EEPROM_PAGE_BITS)
+#define EEPROM_PAGE_MASK (EEPROM_PAGE_SIZE - 1)
+
+#define EEPROM_OFFSET_SIZE 2
+/**
+ * amdgpu_eeprom_xfer -- Read/write from/to an I2C EEPROM device
+ * @i2c_adap: pointer to the I2C adapter to use
+ * @slave_addr: I2C address of the slave device
+ * @eeprom_addr: EEPROM address from which to read/write
+ * @eeprom_buf: pointer to data buffer to read into/write from
+ * @buf_size: the size of @eeprom_buf
+ * @read: True if reading from the EEPROM, false if writing
+ *
+ * Returns the number of bytes read/written; -errno on error.
+ */
int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap,
u16 slave_addr, u16 eeprom_addr,
- u8 *eeprom_buf, u16 bytes, bool read)
+ u8 *eeprom_buf, u16 buf_size, bool read)
{
- u8 eeprom_offset_buf[2];
- u16 bytes_transferred;
+ u8 eeprom_offset_buf[EEPROM_OFFSET_SIZE];
struct i2c_msg msgs[] = {
{
.addr = slave_addr,
.flags = 0,
- .len = EEPROM_OFFSET_LENGTH,
+ .len = EEPROM_OFFSET_SIZE,
.buf = eeprom_offset_buf,
},
{
.addr = slave_addr,
.flags = read ? I2C_M_RD : 0,
- .len = bytes,
- .buf = eeprom_buf,
},
};
+ const u8 *p = eeprom_buf;
int r;
+ u16 len;
+
+ r = 0;
+ for (len = 0; buf_size > 0;
+ buf_size -= len, eeprom_addr += len, eeprom_buf += len) {
+ /* Set the EEPROM address we want to write to/read from.
+ */
+ msgs[0].buf[0] = (eeprom_addr >> 8) & 0xff;
+ msgs[0].buf[1] = eeprom_addr & 0xff;
- msgs[0].buf[0] = ((eeprom_addr >> 8) & 0xff);
- msgs[0].buf[1] = (eeprom_addr & 0xff);
+ if (!read) {
+ /* Write the maximum amount of data, without
+ * crossing the device's page boundary, as per
+ * its spec. Partial page writes are allowed,
+ * starting at any location within the page,
+ * so long as the page boundary isn't crossed
+ * over (actually the page pointer rolls
+ * over).
+ *
+ * As per the AT24CM02 EEPROM spec, after
+ * writing into a page, the I2C driver MUST
+ * terminate the transfer, i.e. in
+ * "i2c_transfer()" below, with a STOP
+ * condition, so that the self-timed write
+ * cycle begins. This is implied for the
+ * "i2c_transfer()" abstraction.
+ */
+ len = min(EEPROM_PAGE_SIZE - (eeprom_addr &
+ EEPROM_PAGE_MASK),
+ (u32)buf_size);
+ } else {
+ /* Reading from the EEPROM has no limitation
+ * on the number of bytes read from the EEPROM
+ * device--they are simply sequenced out.
+ */
+ len = buf_size;
+ }
+ msgs[1].len = len;
+ msgs[1].buf = eeprom_buf;
- while (msgs[1].len) {
r = i2c_transfer(i2c_adap, msgs, ARRAY_SIZE(msgs));
- if (r <= 0)
- return r;
+ if (r < ARRAY_SIZE(msgs))
+ break;
- /* Only for write data */
- if (!msgs[1].flags)
- /*
- * According to EEPROM spec there is a MAX of 10 ms required for
- * EEPROM to flush internal RX buffer after STOP was issued at the
- * end of write transaction. During this time the EEPROM will not be
- * responsive to any more commands - so wait a bit more.
+ if (!read) {
+ /* According to the AT24CM02 EEPROM spec the
+ * length of the self-writing cycle, tWR, is
+ * 10 ms.
*
* TODO Improve to wait for first ACK for slave address after
* internal write cycle done.
*/
msleep(10);
-
-
- bytes_transferred = r - EEPROM_OFFSET_LENGTH;
- eeprom_addr += bytes_transferred;
- msgs[0].buf[0] = ((eeprom_addr >> 8) & 0xff);
- msgs[0].buf[1] = (eeprom_addr & 0xff);
- msgs[1].buf += bytes_transferred;
- msgs[1].len -= bytes_transferred;
+ }
}
- return 0;
+ return r < 0 ? r : eeprom_buf - p;
}
--
2.32.0
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