linux-kernel - Re: [PATCH] mailbox: tegra-hsp: Flush whole channel

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Message-ID: <dea35c3e-c5ff-b7ba-7498-fc67493d96b7@nvidia.com>
Date:   Mon, 14 Feb 2022 15:42:48 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>
Cc:     Mikko Perttunen <mperttunen@...dia.com>,
        Pekka Pessi <ppessi@...dia.com>, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mailbox: tegra-hsp: Flush whole channel


On 14/02/2022 15:32, Thierry Reding wrote:
> From: Pekka Pessi <ppessi@...dia.com>
> 
> The txdone can re-fill the mailbox. Keep polling the mailbox during the
> flush until all the messages have been delivered.
> 
> Signed-off-by: Pekka Pessi <ppessi@...dia.com>
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>   drivers/mailbox/tegra-hsp.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mailbox/tegra-hsp.c b/drivers/mailbox/tegra-hsp.c
> index acd0675da681..78f7265039c6 100644
> --- a/drivers/mailbox/tegra-hsp.c
> +++ b/drivers/mailbox/tegra-hsp.c
> @@ -412,6 +412,11 @@ static int tegra_hsp_mailbox_flush(struct mbox_chan *chan,
>   		value = tegra_hsp_channel_readl(ch, HSP_SM_SHRD_MBOX);
>   		if ((value & HSP_SM_SHRD_MBOX_FULL) == 0) {
>   			mbox_chan_txdone(chan, 0);
> +
> +			/* Wait until channel is empty */
> +			if (chan->active_req != NULL)
> +				continue;
> +
>   			return 0;
>   		}
>   


Thanks!

Tested-by: Jon Hunter <jonathanh@...dia.com>

Maybe worth mentioning that this fixes an annoying issue with the TCU 
(Tegra Combined UART) where the output is getting truncated. I think we 
should add the following fixes tag and mark for stable too.

Fixes: 91b1b1c3da8a ("mailbox: tegra-hsp: Add support for shared mailboxes")

Jon

-- 
nvpublic