On 17.01.2025 18:28, Andy Shevchenko wrote:
> On Fri, Jan 17, 2025 at 05:05:42PM +0100, Marek Szyprowski wrote:
>> On 17.01.2025 15:30, Andy Shevchenko wrote:
>>> On Fri, Jan 17, 2025 at 04:09:58PM +0200, Andy Shevchenko wrote:
>>>> On Fri, Jan 17, 2025 at 02:57:52PM +0100, Marek Szyprowski wrote:
>>>>> On 16.01.2025 13:42, Andy Shevchenko wrote:
>>>>>> If the selector register is represented in each page, its value
>>>>>> in accordance to the debugfs is stale because it gets synchronized
>>>>>> only after the real page switch happens. Synchronize cache for
>>>>>> the page selector.
>>>>>>
>>>>>> Before (offset followed by hexdump, the first byte is selector):
>>>>>>
>>>>>> // Real registers
>>>>>> 18: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
>>>>>> ...
>>>>>> // Virtual (per port)
>>>>>> 40: 05 ff 00 00 e0 e0 00 00 00 00 00 1f
>>>>>> 50: 00 ff 00 00 e0 e0 00 00 00 00 00 1f
>>>>>> 60: 01 ff 00 00 ff ff 00 00 00 00 00 00
>>>>>> 70: 02 ff 00 00 cf f3 00 00 00 00 00 0c
>>>>>> 80: 03 ff 00 00 00 00 00 00 00 00 00 ff
>>>>>> 90: 04 ff 00 00 ff 0f 00 00 f0 00 00 00
>>>>>>
>>>>>> After:
>>>>>>
>>>>>> // Real registers
>>>>>> 18: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
>>>>>> ...
>>>>>> // Virtual (per port)
>>>>>> 40: 00 ff 00 00 e0 e0 00 00 00 00 00 1f
>>>>>> 50: 01 ff 00 00 e0 e0 00 00 00 00 00 1f
>>>>>> 60: 02 ff 00 00 ff ff 00 00 00 00 00 00
>>>>>> 70: 03 ff 00 00 cf f3 00 00 00 00 00 0c
>>>>>> 80: 04 ff 00 00 00 00 00 00 00 00 00 ff
>>>>>> 90: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
>>>>>>
>>>>>> Fixes: 6863ca622759 ("regmap: Add support for register indirect addressing.")
>>>>>> Signed-off-by: Andy Shevchenko<andriy.shevchenko@xxxxxxxxxxxxxxx>
>>>>> This patch landed in linux-next some time ago as commit 1fd60ed1700c
>>>>> ("regmap: Synchronize cache for the page selector"). Today I've noticed
>>>>> that it causes a regression for Lontium LT9611UXC HDMI bridge driver.
>>>> Is there any datasheet link to the HW in question?
>>>>
>>>> (FWIW, I have tested this with the CY8C9540 GPIO I²C expander on Intel Galileo
>>>> Gen 1 board.)
>>>>
>>>>> With today's linux-next I got the following messages on QCom RB5 board:
>>>>>
>>>>> # dmesg | grep lt9611uxc
>>>>> [ 13.737346] lt9611uxc 5-002b: LT9611 revision: 0x00.00.00
>>>>> [ 13.804190] lt9611uxc 5-002b: LT9611 version: 0x00
>>>>> [ 13.870564] lt9611uxc 5-002b: FW version 0, enforcing firmware update
>>>>> [ 13.877437] lt9611uxc 5-002b: Direct firmware load for
>>>>> lt9611uxc_fw.bin failed with error -2
>>>>> [ 13.887517] lt9611uxc 5-002b: probe with driver lt9611uxc failed with
>>>>> error -2
>>>>>
>>>>> after reverting the $subject patch, the driver probes fine on that board.
>>>>>
>>>>> I'm not sure if this is really a bug caused by this change or simply the
>>>>> driver already was aligned to old regmap behavior. Dmitry, could you
>>>>> check the regamp usage and review the changes introduced by this patch?
>>>>> Let me know if there is anything to check on the real hardware to help
>>>>> resolving this issue.
>>>> Yes, see below. And thank you for your report!
> ...
>
>>>>>> + /*
>>>>>> + * If selector register has been just updated, update the respective
>>>>>> + * virtual copy as well.
>>>>>> + */
>>>>>> + if (page_chg &&
>>>>>> + in_range(range->selector_reg, range->window_start, range->window_len))
>>>>>> + _regmap_update_bits(map, sel_register, mask, val, NULL, false);
>>>> Can you add a test printk() here to show
>>>>
>>>> page_chg
>>>> range->selector_reg, range->window_start, range->window_len
>>>> sel_register, mask, val
>>>>
>>>> ?
>>>>
>>>> And would commenting these three lines make it work again?
>>> Also try to apply this patch (while having the above lines not commented):
>> This patch applied alone doesn't change anything. Probe still fails.
>>
>> However, with the mentioned 3 lines in the regmap code commented AND
>> this patch applied, lt9611uxc driver probe also fails.
> Does it fail in the same way?
Yes, the hw revision is reported as zero in this case: LT9611 revision:
0x00.00.00
>> Does it mean that there is really a bug in the driver?
> Without looking at the datasheet it's hard to say. At least what I found so far
> is one page of the I²C traffic dump on Windows as an example how to use their
> evaluation board and software, but it doesn't unveil the bigger picture. At
> least what I think is going on here is that the programming is not so easy as
> just paging. Something is more complicated there.
>
> But at least (and as Mark said) the most of the regmap based drivers got
> the ranges wrong (so, at least there is one bug in the driver).
I can do more experiments if this helps. Do you need a dump of all
regmap accesses or i2c traffic from this driver?
>>> --- a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
>>> +++ b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
>>> @@ -69,7 +69,7 @@ struct lt9611uxc {
>>> static const struct regmap_range_cfg lt9611uxc_ranges[] = {
>>> {
>>> .name = "register_range",
>>> - .range_min = 0,
>>> + .range_min = 0x0100,
>>> .range_max = 0xd0ff,
>>> .selector_reg = LT9611_PAGE_CONTROL,
>>> .selector_mask = 0xff,
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
