| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <5619cca5-6d5b-4682-bbf7-51b851cef37e@kernel.org>
Date: Mon, 8 Jul 2024 08:10:17 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Ferry Toth <ftoth@...londelft.nl>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
John Ogness <john.ogness@...utronix.de>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
linux-serial@...r.kernel.org
Cc: neil.armstrong@...aro.org, AlCooper <alcooperx@...il.com>,
AlexanderShiyan <shc_work@...l.ru>,
AlexandreBelloni <alexandre.belloni@...tlin.com>,
AlexandreTorgue <alexandre.torgue@...s.st.com>,
AlimAkhtar <alim.akhtar@...sung.com>,
AndrewMorton <akpm@...ux-foundation.org>,
"AneeshKumarK . V" <aneesh.kumar@...nel.org>,
AngeloGioacchinoDelRegno <angelogioacchino.delregno@...labora.com>,
BaolinWang <baolin.wang@...ux.alibaba.com>, BaruchSiach <baruch@...s.co.il>,
BjornAndersson <andersson@...nel.org>,
ClaudiuBeznea <claudiu.beznea@...on.dev>,
"DavidS . Miller" <davem@...emloft.net>, FabioEstevam <festevam@...il.com>,
HammerHsieh <hammerh0314@...il.com>,
Christian König <christian.koenig@....com>,
ChristopheLeroy <christophe.leroy@...roup.eu>,
ChunyanZhang <zhang.lyra@...il.com>, JeromeBrunet <jbrunet@...libre.com>,
JonathanHunter <jonathanh@...dia.com>, KevinHilman <khilman@...libre.com>,
KonradDybcio <konrad.dybcio@...aro.org>,
KrzysztofKozlowski <krzysztof.kozlowski@...aro.org>,
KumaravelThiagarajan <kumaravel.thiagarajan@...rochip.com>,
LaxmanDewangan <ldewangan@...dia.com>, linux-arm-kernel@...ts.infradead.org,
linux-arm-msm@...r.kernel.org, "MaciejW . Rozycki" <macro@...am.me.uk>,
ManivannanSadhasivam <manivannan.sadhasivam@...aro.org>,
MartinBlumenstingl <martin.blumenstingl@...glemail.com>,
MatthiasBrugger <matthias.bgg@...il.com>,
MaximeCoquelin <mcoquelin.stm32@...il.com>,
MichaelEllerman <mpe@...erman.id.au>, MichalSimek <michal.simek@....com>,
"NaveenN . Rao" <naveen.n.rao@...ux.ibm.com>,
NicolasFerre <nicolas.ferre@...rochip.com>,
NicholasPiggin <npiggin@...il.com>, OrsonZhai <orsonzhai@...il.com>,
Pali Rohár <pali@...nel.org>,
PatriceChotard <patrice.chotard@...s.st.com>,
PeterKorsgaard <jacmet@...site.dk>, RichardGenoud
<richard.genoud@...il.com>, RussellKing <linux@...linux.org.uk>,
SaschaHauer <s.hauer@...gutronix.de>, ShawnGuo <shawnguo@...nel.org>,
StefaniSeibold <stefani@...bold.net>, SumitSemwal <sumit.semwal@...aro.org>,
TaichiSugaya <sugaya.taichi@...ionext.com>,
TakaoOrito <orito.takao@...ionext.com>,
TharunKumarP <tharunkumar.pasumarthi@...rochip.com>,
ThierryReding <thierry.reding@...il.com>, TimurTabi <timur@...nel.org>,
VineetGupta <vgupta@...nel.org>, MarekSzyprowski <m.szyprowski@...sung.com>,
PhilEdworthy <phil.edworthy@...esas.com>
Subject: Re: [PATCH/RFC v1 1/1] tty: serial: 8250_dma: use sgl with 2 nents to
take care of buffer wrap
On 03. 07. 24, 22:56, Ferry Toth wrote:
> Previously 8250_dma used a circular xmit->buf as DMA output buffer. This
> causes messages that wrap around in the circular buffer to be
> transmitted using 2 DMA transfers. Depending on baud rate and processor
> load this can cause an interchar gap in the middle of the message. On
> the receiving end the gap may cause a short receive timeout, possibly
> long enough to terminate a DMA transfer, but too short to restart a
> receive DMA transfer in time thus causing a receive buffer overrun.
>
> This is especially a problem for devices with high speed UARTs (HSU)
> where even deep 64 byte FIFO's are not sufficient to handle interrupt
> latency.
>
> The circular buffer has now been replaced by kfifo which requires a SG
> list with a single entry, which still causes 2 dma transfers when a wrap
> around occurs. Fix this by allowing up to 2 entries in the sgl.
As I stated earlier, from the DMA and TTY perspective, this looks all
good™. So I welcome this.
From the devices perspective, obviously testers needed ;). I believe we
can merge this in 6.12-rc1 (or even 6.11-rc1?) and see. So please post a
non-RFC patch.
Reviewed-by: Jiri Slaby <jirislaby@...nel.org>
> Signed-off-by: Ferry Toth <ftoth@...londelft.nl>
> ---
> drivers/tty/serial/8250/8250_dma.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
> index 8a353e3cc3dd..d215c494ee24 100644
> --- a/drivers/tty/serial/8250/8250_dma.c
> +++ b/drivers/tty/serial/8250/8250_dma.c
> @@ -89,7 +89,9 @@ int serial8250_tx_dma(struct uart_8250_port *p)
> struct tty_port *tport = &p->port.state->port;
> struct dma_async_tx_descriptor *desc;
> struct uart_port *up = &p->port;
> - struct scatterlist sg;
> + struct scatterlist *sg;
> + struct scatterlist sgl[2];
> + int i;
> int ret;
>
> if (dma->tx_running) {
> @@ -110,18 +112,17 @@ int serial8250_tx_dma(struct uart_8250_port *p)
>
> serial8250_do_prepare_tx_dma(p);
>
> - sg_init_table(&sg, 1);
> - /* kfifo can do more than one sg, we don't (quite yet) */
> - ret = kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, &sg, 1,
> + sg_init_table(sgl, ARRAY_SIZE(sgl));
> +
> + ret = kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, sgl, ARRAY_SIZE(sgl),
> UART_XMIT_SIZE, dma->tx_addr);
>
> - /* we already checked empty fifo above, so there should be something */
> - if (WARN_ON_ONCE(ret != 1))
> - return 0;
> + dma->tx_size = 0;
>
> - dma->tx_size = sg_dma_len(&sg);
> + for_each_sg(sgl, sg, ret, i)
> + dma->tx_size += sg_dma_len(sg);
>
> - desc = dmaengine_prep_slave_sg(dma->txchan, &sg, 1,
> + desc = dmaengine_prep_slave_sg(dma->txchan, sgl, ret,
> DMA_MEM_TO_DEV,
> DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> if (!desc) {
--
js
Powered by blists - more mailing lists