linux-kernel - Re: [PATCH v3 1/1] regmap: Synchronize cache for the page selector

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Message-ID: <c2c2f613-3b65-4efe-99c2-135f043b2d3b@samsung.com>
Date: Wed, 29 Jan 2025 18:50:57 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org, Greg
	Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
	<rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>, Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>, DRI mailing list
	<dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v3 1/1] regmap: Synchronize cache for the page selector

On 29.01.2025 16:07, Andy Shevchenko wrote:
>> [...]
> Meanwhile, can you test this patch (on top of non-working case)?
>
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index 2314744201b4..f799a7a80231 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -1553,8 +1553,19 @@ static int _regmap_select_page(struct regmap *map, unsigned int *reg,
>   		 * virtual copy as well.
>   		 */
>   		if (page_chg &&
> -		    in_range(range->selector_reg, range->window_start, range->window_len))
> +		    in_range(range->selector_reg, range->window_start, range->window_len)) {
> +			bool bypass, cache_only;
> +
> +			bypass = map->cache_bypass;
> +			cache_only = map->cache_only;
> +			map->cache_bypass = false;
> +			map->cache_only = true;
> +
>   			_regmap_update_bits(map, sel_register, mask, val, NULL, false);
> +
> +			map->cache_bypass = bypass;
> +			map->cache_only = cache_only;
> +		}
>   	}
>   
>   	*reg = range->window_start + win_offset;
>
> If I understood the case, the affected driver doesn't use case and we actually
> write to the selector register twice which most likely messes up the things.
> But this is only a theory (since we don't have the traces yet).

Bingo! This patch (on top of current linux-next) fixed the probe issue. 
Feel free to add:

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

(although I'm not sure if this is a fix for the generic case or just 
this driver)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland