From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 41211C433F5 for ; Mon, 29 Nov 2021 16:36:23 +0000 (UTC) Received: from localhost ([::1]:40616 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mrjde-0003Jl-9R for qemu-devel@archiver.kernel.org; Mon, 29 Nov 2021 11:36:22 -0500 Received: from eggs.gnu.org ([209.51.188.92]:46918) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mrjch-0002Mi-4S for qemu-devel@nongnu.org; Mon, 29 Nov 2021 11:35:23 -0500 Received: from [2a00:1450:4864:20::233] (port=46653 helo=mail-lj1-x233.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mrjce-0004Qz-Az for qemu-devel@nongnu.org; Mon, 29 Nov 2021 11:35:22 -0500 Received: by mail-lj1-x233.google.com with SMTP id e11so35488594ljo.13 for ; Mon, 29 Nov 2021 08:35:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ledger.fr; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=69n8nWHU2/ZqQENjZoeWKHlT6wJanKn5qutQopApahc=; b=JhGNP8bdbdAjzri8+HHK4YPMhJeisXFHdi5hN3VWWNmnW1p/9cuRQRZtIEsnDwTAsW 5+zasuvZCFbC/M12YG9xqXnLg7HeDWT203N3eDRzDTl/VHeKhHTixCGAGVAMA4sUwfvB sBPCA4KvrO58n7Oy2bhfIcj7SC8vRNf0+XprXlZ42Q9nlomo4j8aGjVQkeF3BNo9FxrL qJAq5x5jRDRNdAUC/Bx1Z43t+kfdY7/tRJ5lWcAFikpRES+XFIQlgFQkce1MjB4RJXnE wJW06X+c4Cy6mprqbm5St0B8MbN9+2rugh4IcN3RPGUBaUd0Plrk0NXm3d60NsveHhNG muGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=69n8nWHU2/ZqQENjZoeWKHlT6wJanKn5qutQopApahc=; b=NaO1OEIzDc1s5OW+1aftRmJgWUw/kcsqPCeIGZLLA06B4G7xzbKpcwUwVKizXT04h7 XjhIT6Q+84/K0dC+OazAp7SraGEliO1OA4O/8xYWJrEyBMffl08cqZsjIC32t5DGyGUy iw+upAxT1A2rSoGz+h6kT2Jj8xuhUdmGr4zuMGSRsmIeNMJocJyLHIWwYOxeT9MD4BE6 uqv7VRQE9LCgJPRd32O2n0RkFJf6agqfLnHdMF70WpccNduSmL+DkWjaNkfKK0lqA/zv UpZTOW73bHml+filAyy/I8ej7OEhD6eAVFRmVB8O8GvN8MpmA9+PrFKvSRB8X4+Lh2f5 P1Mg== X-Gm-Message-State: AOAM533eq8J/5lWaWpgXl2JhgdVbqBS9jgybgKjuSWoTMok2N/3/6BDm B14n+/QjOt7n7eHOio4K+8TbuBLwpRznHSNLey7r7eUuC9cyUabDyze0ee8rdxDpianfNIAgeE6 pKqG+pEsznLOU1pY6/2vfUeKm X-Google-Smtp-Source: ABdhPJzC+d7xWLJ/N156Hp8uNERkMDP50mloUFXRQGCgx5LWWa52pCeC2wHTx1ar/Ie9Ywt+ah5h1SZzkPh289k43tU= X-Received: by 2002:a2e:3a18:: with SMTP id h24mr52551666lja.372.1638203717356; Mon, 29 Nov 2021 08:35:17 -0800 (PST) MIME-Version: 1.0 References: <20211128120723.4053-1-olivier.heriveaux@ledger.fr> In-Reply-To: From: Olivier Heriveaux Date: Mon, 29 Nov 2021 17:35:06 +0100 Message-ID: Subject: Re: [PATCH] Fix STM32F2XX USART data register readout To: Peter Maydell Cc: qemu-devel@nongnu.org, qemu-trivial@nongnu.org, alistair@alistair23.me Content-Type: multipart/alternative; boundary="000000000000a4a7c405d1f00689" X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::233 (failed) Received-SPF: permerror client-ip=2a00:1450:4864:20::233; envelope-from=olivier.heriveaux@ledger.fr; helo=mail-lj1-x233.google.com X-Spam_score_int: 14 X-Spam_score: 1.4 X-Spam_bar: + X-Spam_report: (1.4 / 5.0 requ) BAYES_50=0.8, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=0.001, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --000000000000a4a7c405d1f00689 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable If I understand correctly (I'm not a QEmu internals expert), yes this is what happens. Maybe stm32f2xx_usart_can_receive() is also called but since the USART_SR_RXNE flag is reset before the USART_DR is read, it does not prevent reading the next character. Best regards, Olivier H=C3=A9riveaux Le lun. 29 nov. 2021 =C3=A0 11:46, Peter Maydell = a =C3=A9crit : > On Sun, 28 Nov 2021 at 12:07, Olivier H=C3=A9riveaux > wrote: > > > > Fix issue where the data register may be overwritten by next character > > reception before being read and returned. > > > > Signed-off-by: Olivier H=C3=A9riveaux > > --- > > hw/char/stm32f2xx_usart.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/hw/char/stm32f2xx_usart.c b/hw/char/stm32f2xx_usart.c > > index 8df0832424..fde67f4f03 100644 > > --- a/hw/char/stm32f2xx_usart.c > > +++ b/hw/char/stm32f2xx_usart.c > > @@ -103,10 +103,11 @@ static uint64_t stm32f2xx_usart_read(void *opaque= , > hwaddr addr, > > return retvalue; > > case USART_DR: > > DB_PRINT("Value: 0x%" PRIx32 ", %c\n", s->usart_dr, (char) > s->usart_dr); > > + retvalue =3D s->usart_dr & 0x3FF; > > s->usart_sr &=3D ~USART_SR_RXNE; > > qemu_chr_fe_accept_input(&s->chr); > > qemu_set_irq(s->irq, 0); > > - return s->usart_dr & 0x3FF; > > + return retvalue; > > case USART_BRR: > > return s->usart_brr; > > case USART_CR1: > > -- > > 2.17.1 > > The bug happens because qemu_chr_fe_accept_input() can cause > stm32f2xx_usart_receive() to be called, right ? > > Reviewed-by: Peter Maydell > > I'll put this in my list of patches to take via target-arm.next for the > 7.0 release. > > thanks > -- PMM > --=20 Les informations contenues dans ce message =C3=A9lectronique ainsi que cell= es=20 contenues dans les documents attach=C3=A9s sont strictement confidentielles= et=20 sont destin=C3=A9es =C3=A0 l'usage exclusif du (des) destinataire(s) nomm= =C3=A9(s). Toute=20 divulgation, distribution ou reproduction, m=C3=AAme partielle, en est=20 strictement interdite sauf autorisation =C3=A9crite et expresse de l=E2=80= =99=C3=A9metteur. Si vous recevez ce message par erreur, veuillez le notifier imm=C3=A9diatem= ent =C3=A0=20 son =C3=A9metteur par retour, et le d=C3=A9truire ainsi que tous les docume= nts qui y=20 sont attach=C3=A9s. The information contained in this email and in any=20 document enclosed is strictly confidential and is intended solely for the= =20 use of the individual or entity to which it is addressed. Partial or total=20 disclosure, distribution or reproduction of its contents is strictly=20 prohibited unless expressly approved in writing by the sender. If you have=20 received this communication in error, please notify us immediately by=20 responding to this email, and then delete the message and its attached=20 files from your system. --000000000000a4a7c405d1f00689 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
If I understand correctly (I'm not a QEmu internals ex= pert), yes this is what happens.
Maybe=C2=A0stm32f2xx_usart_can_receive= () is also called but since the USART_SR_RXNE flag is reset before the USAR= T_DR is read, it does not prevent reading the next character.
Best regards,
Olivier H=C3=A9riveaux

<= div class=3D"gmail_quote">
Le=C2=A0lun= . 29 nov. 2021 =C3=A0=C2=A011:46, Peter Maydell <peter.maydell@linaro.org> a =C3=A9crit=C2=A0:
On Sun, 28 Nov 20= 21 at 12:07, Olivier H=C3=A9riveaux
<olivie= r.heriveaux@ledger.fr> wrote:
>
> Fix issue where the data register may be overwritten by next character=
> reception before being read and returned.
>
> Signed-off-by: Olivier H=C3=A9riveaux <olivier.heriveaux@ledger.fr> > ---
>=C2=A0 hw/char/stm32f2xx_usart.c | 3 ++-
>=C2=A0 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/char/stm32f2xx_usart.c b/hw/char/stm32f2xx_usart.c
> index 8df0832424..fde67f4f03 100644
> --- a/hw/char/stm32f2xx_usart.c
> +++ b/hw/char/stm32f2xx_usart.c
> @@ -103,10 +103,11 @@ static uint64_t stm32f2xx_usart_read(void *opaqu= e, hwaddr addr,
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return retvalue;
>=C2=A0 =C2=A0 =C2=A0 case USART_DR:
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 DB_PRINT("Value: 0x%" PRIx= 32 ", %c\n", s->usart_dr, (char) s->usart_dr);
> +=C2=A0 =C2=A0 =C2=A0 =C2=A0 retvalue =3D s->usart_dr & 0x3FF;<= br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 s->usart_sr &=3D ~USART_SR_RX= NE;
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 qemu_chr_fe_accept_input(&s->= chr);
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 qemu_set_irq(s->irq, 0);
> -=C2=A0 =C2=A0 =C2=A0 =C2=A0 return s->usart_dr & 0x3FF;
> +=C2=A0 =C2=A0 =C2=A0 =C2=A0 return retvalue;
>=C2=A0 =C2=A0 =C2=A0 case USART_BRR:
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return s->usart_brr;
>=C2=A0 =C2=A0 =C2=A0 case USART_CR1:
> --
> 2.17.1

The bug happens because qemu_chr_fe_accept_input() can cause
stm32f2xx_usart_receive() to be called, right ?

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

I'll put this in my list of patches to take via target-arm.next for the=
7.0 release.

thanks
-- PMM

Les i= nformations contenues dans ce message =C3=A9lectronique ainsi que celles co= ntenues dans les documents attach=C3=A9s sont strictement confidentielles e= t sont destin=C3=A9es =C3=A0 l'usage exclusif du (des) destinataire(s) = nomm=C3=A9(s).
Toute divulgation, distribution ou reproduction, m=C3=AAme partielle= , en est strictement interdite sauf autorisation =C3=A9crite et expresse de= l=E2=80=99=C3=A9metteur.
Si vous recevez ce message par erreur, veuillez le notifi= er imm=C3=A9diatement =C3=A0 son =C3=A9metteur par retour, et le d=C3=A9tru= ire ainsi que tous les documents qui y sont attach=C3=A9s.

The information contained i= n this email and in any document enclosed is strictly confidential and is i= ntended solely for the use of the individual or entity to which it is addre= ssed.
Pa= rtial or total disclosure, distribution or reproduction of its contents is = strictly prohibited unless expressly approved in writing by the sender.
If you have= received this communication in error, please notify us immediately by resp= onding to this email, and then delete the message and its attached files fr= om your system.
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