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linux/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
Alvin Šipraga ab0af093bf drm: bridge: adv7511: use non-legacy mode for CEC RX 
The ADV7511 family of bridges supports two modes for CEC RX: legacy and
non-legacy mode. The only difference is whether the chip uses a single
CEC RX buffer, or uses all three available RX buffers. Currently the
adv7511 driver uses legacy mode.

While debugging a stall in CEC RX on an ADV7535, we reached out to
Analog Devices, who suggested to use non-legacy mode instead.  According
to the programming guide for the ADV7511 [1], and the register control
manual of the ADV7535 [2], this is the default behaviour on reset. As
previously stated, the adv7511 driver currently overrides this to legacy
mode.

This patch updates the adv7511 driver to instead use non-legacy mode
with all three CEC RX buffers. As a result of this change, we no longer
experience any stalling of CEC RX with the ADV7535. It is not known why
non-legacy mode solves this particular issue, but besides this, no
functional change is to be expected by this patch. Please note that this
has only been tested on an ADV7535.

What follows is a brief description of the non-legacy mode interrupt
handling behaviour. The programming guide in [1] gives a more detailed
explanation.

With three RX buffers, the interrupt handler checks the CEC_RX_STATUS
register (renamed from CEC_RX_ENABLE in this patch), which contains
2-bit psuedo-timestamps for each of the RX buffers. The RX timestamps
for each buffer represent the time of arrival for the CEC frame held in
a given buffer, with lower timestamp values indicating chronologically
older frames. A special value of 0 indicates that the given RX buffer
is inactive and should be skipped. The interrupt handler parses these
timestamps and then reads the active RX buffers in the prescribed order
using the same logic as before. Changes have been made to ensure that
the correct RX buffer is cleared after processing. This clearing
procesure also sets the timestamp of the given RX buffer to 0 to mark it
as inactive.

[1] https://www.analog.com/media/en/technical-documentation/user-guides/ADV7511_Programming_Guide.pdf
    cf. CEC Map, register 0x4A, bit 3, default value 1:
    0 = Use only buffer 0 to store CEC frames (Legacy mode)
    1 = Use all 3 buffers to stores the CEC frames (Non-legacy mode)

[2] The ADV7535 register control manual is under NDA, but trust me when
    I say that non-legacy CEC RX mode is the default here too. Here the
    register is offset by 0x70 and has an address of 0xBA in the DSI_CEC
    regiser map.

Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220423120854.1503163-3-alvin@pqrs.dk
2022-05-02 16:38:47 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* adv7511_cec.c - Analog Devices ADV7511/33 cec driver
*
* Copyright 2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
*/
#include <linux/device.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/clk.h>
#include <media/cec.h>
#include "adv7511.h"
#define ADV7511_INT1_CEC_MASK \
(ADV7511_INT1_CEC_TX_READY | ADV7511_INT1_CEC_TX_ARBIT_LOST | \
ADV7511_INT1_CEC_TX_RETRY_TIMEOUT | ADV7511_INT1_CEC_RX_READY1 | \
ADV7511_INT1_CEC_RX_READY2 | ADV7511_INT1_CEC_RX_READY3)
static void adv_cec_tx_raw_status(struct adv7511 *adv7511, u8 tx_raw_status)
{
unsigned int offset = adv7511->reg_cec_offset;
unsigned int val;
if (regmap_read(adv7511->regmap_cec,
ADV7511_REG_CEC_TX_ENABLE + offset, &val))
return;
if ((val & 0x01) == 0)
return;
if (tx_raw_status & ADV7511_INT1_CEC_TX_ARBIT_LOST) {
cec_transmit_attempt_done(adv7511->cec_adap,
CEC_TX_STATUS_ARB_LOST);
return;
}
if (tx_raw_status & ADV7511_INT1_CEC_TX_RETRY_TIMEOUT) {
u8 status;
u8 err_cnt = 0;
u8 nack_cnt = 0;
u8 low_drive_cnt = 0;
unsigned int cnt;
/*
* We set this status bit since this hardware performs
* retransmissions.
*/
status = CEC_TX_STATUS_MAX_RETRIES;
if (regmap_read(adv7511->regmap_cec,
ADV7511_REG_CEC_TX_LOW_DRV_CNT + offset, &cnt)) {
err_cnt = 1;
status |= CEC_TX_STATUS_ERROR;
} else {
nack_cnt = cnt & 0xf;
if (nack_cnt)
status |= CEC_TX_STATUS_NACK;
low_drive_cnt = cnt >> 4;
if (low_drive_cnt)
status |= CEC_TX_STATUS_LOW_DRIVE;
}
cec_transmit_done(adv7511->cec_adap, status,
0, nack_cnt, low_drive_cnt, err_cnt);
return;
}
if (tx_raw_status & ADV7511_INT1_CEC_TX_READY) {
cec_transmit_attempt_done(adv7511->cec_adap, CEC_TX_STATUS_OK);
return;
}
}
static void adv7511_cec_rx(struct adv7511 *adv7511, int rx_buf)
{
unsigned int offset = adv7511->reg_cec_offset;
struct cec_msg msg = {};
unsigned int len;
unsigned int val;
u8 i;
if (regmap_read(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_FRAME_LEN[rx_buf] + offset, &len))
return;
msg.len = len & 0x1f;
if (msg.len > 16)
msg.len = 16;
if (!msg.len)
return;
for (i = 0; i < msg.len; i++) {
regmap_read(adv7511->regmap_cec,
i + ADV7511_REG_CEC_RX_FRAME_HDR[rx_buf] + offset,
&val);
msg.msg[i] = val;
}
/* Toggle RX Ready Clear bit to re-enable this RX buffer */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_BUFFERS + offset, BIT(rx_buf),
BIT(rx_buf));
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_BUFFERS + offset, BIT(rx_buf), 0);
cec_received_msg(adv7511->cec_adap, &msg);
}
void adv7511_cec_irq_process(struct adv7511 *adv7511, unsigned int irq1)
{
unsigned int offset = adv7511->reg_cec_offset;
const u32 irq_tx_mask = ADV7511_INT1_CEC_TX_READY |
ADV7511_INT1_CEC_TX_ARBIT_LOST |
ADV7511_INT1_CEC_TX_RETRY_TIMEOUT;
const u32 irq_rx_mask = ADV7511_INT1_CEC_RX_READY1 |
ADV7511_INT1_CEC_RX_READY2 |
ADV7511_INT1_CEC_RX_READY3;
unsigned int rx_status;
int rx_order[3] = { -1, -1, -1 };
int i;
if (irq1 & irq_tx_mask)
adv_cec_tx_raw_status(adv7511, irq1);
if (!(irq1 & irq_rx_mask))
return;
if (regmap_read(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_STATUS + offset, &rx_status))
return;
/*
* ADV7511_REG_CEC_RX_STATUS[5:0] contains the reception order of RX
* buffers 0, 1, and 2 in bits [1:0], [3:2], and [5:4] respectively.
* The values are to be interpreted as follows:
*
* 0 = buffer unused
* 1 = buffer contains oldest received frame (if applicable)
* 2 = buffer contains second oldest received frame (if applicable)
* 3 = buffer contains third oldest received frame (if applicable)
*
* Fill rx_order with the sequence of RX buffer indices to
* read from in order, where -1 indicates that there are no
* more buffers to process.
*/
for (i = 0; i < 3; i++) {
unsigned int timestamp = (rx_status >> (2 * i)) & 0x3;
if (timestamp)
rx_order[timestamp - 1] = i;
}
/* Read CEC RX buffers in the appropriate order as prescribed above */
for (i = 0; i < 3; i++) {
int rx_buf = rx_order[i];
if (rx_buf < 0)
break;
adv7511_cec_rx(adv7511, rx_buf);
}
}
static int adv7511_cec_adap_enable(struct cec_adapter *adap, bool enable)
{
struct adv7511 *adv7511 = cec_get_drvdata(adap);
unsigned int offset = adv7511->reg_cec_offset;
if (adv7511->i2c_cec == NULL)
return -EIO;
if (!adv7511->cec_enabled_adap && enable) {
/* power up cec section */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_CLK_DIV + offset,
0x03, 0x01);
/* non-legacy mode and clear all rx buffers */
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_BUFFERS + offset, 0x0f);
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_BUFFERS + offset, 0x08);
/* initially disable tx */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_TX_ENABLE + offset, 1, 0);
/* enabled irqs: */
/* tx: ready */
/* tx: arbitration lost */
/* tx: retry timeout */
/* rx: ready 1-3 */
regmap_update_bits(adv7511->regmap,
ADV7511_REG_INT_ENABLE(1), 0x3f,
ADV7511_INT1_CEC_MASK);
} else if (adv7511->cec_enabled_adap && !enable) {
regmap_update_bits(adv7511->regmap,
ADV7511_REG_INT_ENABLE(1), 0x3f, 0);
/* disable address mask 1-3 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_MASK + offset,
0x70, 0x00);
/* power down cec section */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_CLK_DIV + offset,
0x03, 0x00);
adv7511->cec_valid_addrs = 0;
}
adv7511->cec_enabled_adap = enable;
return 0;
}
static int adv7511_cec_adap_log_addr(struct cec_adapter *adap, u8 addr)
{
struct adv7511 *adv7511 = cec_get_drvdata(adap);
unsigned int offset = adv7511->reg_cec_offset;
unsigned int i, free_idx = ADV7511_MAX_ADDRS;
if (!adv7511->cec_enabled_adap)
return addr == CEC_LOG_ADDR_INVALID ? 0 : -EIO;
if (addr == CEC_LOG_ADDR_INVALID) {
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_MASK + offset,
0x70, 0);
adv7511->cec_valid_addrs = 0;
return 0;
}
for (i = 0; i < ADV7511_MAX_ADDRS; i++) {
bool is_valid = adv7511->cec_valid_addrs & (1 << i);
if (free_idx == ADV7511_MAX_ADDRS && !is_valid)
free_idx = i;
if (is_valid && adv7511->cec_addr[i] == addr)
return 0;
}
if (i == ADV7511_MAX_ADDRS) {
i = free_idx;
if (i == ADV7511_MAX_ADDRS)
return -ENXIO;
}
adv7511->cec_addr[i] = addr;
adv7511->cec_valid_addrs |= 1 << i;
switch (i) {
case 0:
/* enable address mask 0 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_MASK + offset,
0x10, 0x10);
/* set address for mask 0 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_0_1 + offset,
0x0f, addr);
break;
case 1:
/* enable address mask 1 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_MASK + offset,
0x20, 0x20);
/* set address for mask 1 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_0_1 + offset,
0xf0, addr << 4);
break;
case 2:
/* enable address mask 2 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_MASK + offset,
0x40, 0x40);
/* set address for mask 1 */
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_LOG_ADDR_2 + offset,
0x0f, addr);
break;
}
return 0;
}
static int adv7511_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,
u32 signal_free_time, struct cec_msg *msg)
{
struct adv7511 *adv7511 = cec_get_drvdata(adap);
unsigned int offset = adv7511->reg_cec_offset;
u8 len = msg->len;
unsigned int i;
/*
* The number of retries is the number of attempts - 1, but retry
* at least once. It's not clear if a value of 0 is allowed, so
* let's do at least one retry.
*/
regmap_update_bits(adv7511->regmap_cec,
ADV7511_REG_CEC_TX_RETRY + offset,
0x70, max(1, attempts - 1) << 4);
/* blocking, clear cec tx irq status */
regmap_update_bits(adv7511->regmap, ADV7511_REG_INT(1), 0x38, 0x38);
/* write data */
for (i = 0; i < len; i++)
regmap_write(adv7511->regmap_cec,
i + ADV7511_REG_CEC_TX_FRAME_HDR + offset,
msg->msg[i]);
/* set length (data + header) */
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_TX_FRAME_LEN + offset, len);
/* start transmit, enable tx */
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_TX_ENABLE + offset, 0x01);
return 0;
}
static const struct cec_adap_ops adv7511_cec_adap_ops = {
.adap_enable = adv7511_cec_adap_enable,
.adap_log_addr = adv7511_cec_adap_log_addr,
.adap_transmit = adv7511_cec_adap_transmit,
};
static int adv7511_cec_parse_dt(struct device *dev, struct adv7511 *adv7511)
{
adv7511->cec_clk = devm_clk_get(dev, "cec");
if (IS_ERR(adv7511->cec_clk)) {
int ret = PTR_ERR(adv7511->cec_clk);
adv7511->cec_clk = NULL;
return ret;
}
clk_prepare_enable(adv7511->cec_clk);
adv7511->cec_clk_freq = clk_get_rate(adv7511->cec_clk);
return 0;
}
int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511)
{
unsigned int offset = adv7511->reg_cec_offset;
int ret = adv7511_cec_parse_dt(dev, adv7511);
if (ret)
goto err_cec_parse_dt;
adv7511->cec_adap = cec_allocate_adapter(&adv7511_cec_adap_ops,
adv7511, dev_name(dev), CEC_CAP_DEFAULTS, ADV7511_MAX_ADDRS);
if (IS_ERR(adv7511->cec_adap)) {
ret = PTR_ERR(adv7511->cec_adap);
goto err_cec_alloc;
}
regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset, 0);
/* cec soft reset */
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_SOFT_RESET + offset, 0x01);
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_SOFT_RESET + offset, 0x00);
/* non-legacy mode - use all three RX buffers */
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_RX_BUFFERS + offset, 0x08);
regmap_write(adv7511->regmap_cec,
ADV7511_REG_CEC_CLK_DIV + offset,
((adv7511->cec_clk_freq / 750000) - 1) << 2);
ret = cec_register_adapter(adv7511->cec_adap, dev);
if (ret)
goto err_cec_register;
return 0;
err_cec_register:
cec_delete_adapter(adv7511->cec_adap);
adv7511->cec_adap = NULL;
err_cec_alloc:
dev_info(dev, "Initializing CEC failed with error %d, disabling CEC\n",
ret);
err_cec_parse_dt:
regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
ADV7511_CEC_CTRL_POWER_DOWN);
return ret == -EPROBE_DEFER ? ret : 0;
}
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