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drm/bridge: ti-sn65dsi86: Check bridge connection failure

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Read out and check the ID registers, so we can bail out if I2C
communication does not work or if the device is unknown. Tested on a
Renesas GrayHawk board (R-Car V4M) by using a wrong I2C address and by
not enabling RuntimePM for the device.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250318155549.19625-2-wsa+renesas@sang-engineering.com
This commit is contained in:
Wolfram Sang
2025-03-18 16:52:56 +01:00
committed by Douglas Anderson
parent 1d1f7b15cb
commit d69362f55f
1 changed files with 12 additions and 0 deletions
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12
drivers/gpu/drm/bridge/ti-sn65dsi86.c
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@@ -35,6 +35,7 @@
#include <drm/drm_print.h>
#include <drm/drm_probe_helper.h>
#define SN_DEVICE_ID_REGS 0x00 /* up to 0x07 */
#define SN_DEVICE_REV_REG 0x08
#define SN_DPPLL_SRC_REG 0x0A
#define DPPLL_CLK_SRC_DSICLK BIT(0)
@@ -1898,6 +1899,7 @@ static int ti_sn65dsi86_probe(struct i2c_client *client)
{
struct device *dev = &client->dev;
struct ti_sn65dsi86 *pdata;
u8 id_buf[8];
int ret;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
@@ -1941,6 +1943,16 @@ static int ti_sn65dsi86_probe(struct i2c_client *client)
if (ret)
return ret;
pm_runtime_get_sync(dev);
ret = regmap_bulk_read(pdata->regmap, SN_DEVICE_ID_REGS, id_buf, ARRAY_SIZE(id_buf));
pm_runtime_put_autosuspend(dev);
if (ret)
return dev_err_probe(dev, ret, "failed to read device id\n");
/* The ID string is stored backwards */
if (strncmp(id_buf, "68ISD ", ARRAY_SIZE(id_buf)))
return dev_err_probe(dev, -EOPNOTSUPP, "unsupported device id\n");
/*
* Break ourselves up into a collection of aux devices. The only real
* motiviation here is to solve the chicken-and-egg problem of probe