Messages in this thread | | | Date | Tue, 26 Jul 2022 10:37:50 +0200 | Subject | Re: [PATCH] watchdog: mtk_wdt: Move mt6589-wdt fallback compatible to end of list | From | AngeloGioacchino Del Regno <> |
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Il 26/07/22 08:20, Chen-Yu Tsai ha scritto: > The watchdog facility in the MediaTek SoCs are all the same, but the > hardware block also contains a reset controller, which differs in the > number of resets used between different SoCs. This difference is > supported with of_device_get_match_data() supplying the number of reset > lines for the newer compatible strings. The original mt6589-wdt only > covers the watchdog facility. > > of_device_is_compatible(), and by extension of_device_get_match_data(), > works by going through the given list of compatible strings sequentially, > and checks if any of the device node's compatible strings match. > > To avoid early matching on the "mediatek,mt6589-wdt" fallback compatible, > which only provides watchdog functionality and no reset controller, move > the fallback entry to the end of the list, so that other, more specific > compatible strings have a chance at getting matched. > > Fixes: c254e103082b ("watchdog: mtk_wdt: mt8183: Add reset controller") > Fixes: adc318a34066 ("watchdog: mt8192: add wdt support") > Fixes: 8c6b5ea6ac68 ("watchdog: mediatek: mt8195: add wdt support") > Fixes: 4dbabc4d9e8c ("watchdog: mediatek: mt8186: add wdt support") > Fixes: 711a5b25bac9 ("watchdog: mtk_wdt: mt7986: Add toprgu reset controller support") > Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Uhm, I don't think that this is an issue?
Ordering precedence is given to the list that you specify in devicetree, that's why "the second one" is a fallback, meaning: ("impossible" example below)
compatible = "mediatek,mt8195-wdt", "mediatek,mt8183-wdt", "mediatek,mt6589-wdt";
This gets walked as per the order in which you wrote the compatibles, so: * Check match for mt8195-wdt, does not exist? * Check match for mt8183-wdt, exists! * Put everything into dev->of_node (having mediatek,mt8183-wdt only!)
__of_device_is_compatible() gets dev->of_node and compares that to all of the possible matches.
struct device_node for this device hence does *not* contain any of the other compatibles that we specified in devicetree, so it does *not* contain any of "mediatek,mt8195-wdt", or "mediatek,mt6589-wdt", because we have previously successfully matches 8183.
I don't think that I've misinterpreted this flow, but if I have, let's pull in devicetree people and check with them?
Cheers, Angelo
> --- > > This change complements the removal of the fallback compatible from the > bindings and DTSI files [1]. > > [1] https://lore.kernel.org/linux-mediatek/20220721014845.19044-1-allen-kh.cheng@mediatek.com/ > > drivers/watchdog/mtk_wdt.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c > index e97787536792..3d5a239b93ba 100644 > --- a/drivers/watchdog/mtk_wdt.c > +++ b/drivers/watchdog/mtk_wdt.c > @@ -425,12 +425,13 @@ static int mtk_wdt_resume(struct device *dev) > > static const struct of_device_id mtk_wdt_dt_ids[] = { > { .compatible = "mediatek,mt2712-wdt", .data = &mt2712_data }, > - { .compatible = "mediatek,mt6589-wdt" }, > { .compatible = "mediatek,mt7986-wdt", .data = &mt7986_data }, > { .compatible = "mediatek,mt8183-wdt", .data = &mt8183_data }, > { .compatible = "mediatek,mt8186-wdt", .data = &mt8186_data }, > { .compatible = "mediatek,mt8192-wdt", .data = &mt8192_data }, > { .compatible = "mediatek,mt8195-wdt", .data = &mt8195_data }, > + /* Fallback compatible string must be last entry */ > + { .compatible = "mediatek,mt6589-wdt" }, > { /* sentinel */ } > }; > MODULE_DEVICE_TABLE(of, mtk_wdt_dt_ids);
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