From: Sam Protsenko <semen.protsenko@linaro.org> To: Jaewon Kim <jaewon02.kim@samsung.com> Cc: Andi Shyti <andi.shyti@kernel.org>, Mark Brown <broonie@kernel.org>, Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>, Alim Akhtar <alim.akhtar@samsung.com>, linux-spi@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] spi: s3c64xx: Use DMA mode from fifo size Date: Thu, 28 Mar 2024 12:58:07 -0500 [thread overview] Message-ID: <CAPLW+4k4qh4ZYBufZoGbUZN0yxSE2X8bOdkEQVw1Zg9YUVpbug@mail.gmail.com> (raw) In-Reply-To: <20240327033041.83625-1-jaewon02.kim@samsung.com> On Tue, Mar 26, 2024 at 10:35 PM Jaewon Kim <jaewon02.kim@samsung.com> wrote: > > The SPI data size is smaller than FIFO, it operates in PIO mode, Spelling: "The" -> "If the" > and if it is larger than FIFO mode, DMA mode is selected. > > If the data size is the same as the FIFO size, it operates in PIO mode > and data is separated into two transfer. In order to prevent, Nit: "transfer" -> "transfers", "prevent" -> "prevent it" > DMA mode must be used from the case of FIFO and data size. > You probably mean this code (it occurs two times in the driver): xfer->len = fifo_len - 1; Can you please elaborate on why it's done this way? Why can't we just do "xfer->len = fifo_len" and use the whole FIFO for the transfer instead? I don't understand the necessity to split the transfer into two chunks if its size is of FIFO length -- wouldn't it fit into FIFO in that case? (I'm pretty sure this change is correct, just want to understand how exactly it works). > Fixes: 1ee806718d5e ("spi: s3c64xx: support interrupt based pio mode") Just wonder if that fixes some throughput regression, or something worse (like failed transfers when the transfer size is the same as FIFO size)? > Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com> > --- > drivers/spi/spi-s3c64xx.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c > index 9fcbe040cb2f..81ed5fddf83e 100644 > --- a/drivers/spi/spi-s3c64xx.c > +++ b/drivers/spi/spi-s3c64xx.c > @@ -430,7 +430,7 @@ static bool s3c64xx_spi_can_dma(struct spi_controller *host, > struct s3c64xx_spi_driver_data *sdd = spi_controller_get_devdata(host); > > if (sdd->rx_dma.ch && sdd->tx_dma.ch) > - return xfer->len > sdd->fifo_depth; > + return xfer->len >= sdd->fifo_depth; > > return false; > } > @@ -826,11 +826,11 @@ static int s3c64xx_spi_transfer_one(struct spi_controller *host, > return status; > } > > - if (!is_polling(sdd) && (xfer->len > fifo_len) && > + if (!is_polling(sdd) && xfer->len >= fifo_len && > sdd->rx_dma.ch && sdd->tx_dma.ch) { > use_dma = 1; > Would be nice to remove this empty line, while at it. > - } else if (xfer->len >= fifo_len) { > + } else if (xfer->len > fifo_len) { Below in the same function I can see similar code: if (target_len >= fifo_len) xfer->len = fifo_len - 1; Shouldn't that 'if' condition be fixed too? Or it's ok as it is? (Just noticed it by searching, not sure myself, hence asking). > tx_buf = xfer->tx_buf; > rx_buf = xfer->rx_buf; > origin_len = xfer->len; > -- > 2.43.2 > >
WARNING: multiple messages have this Message-ID (diff)
From: Sam Protsenko <semen.protsenko@linaro.org> To: Jaewon Kim <jaewon02.kim@samsung.com> Cc: Andi Shyti <andi.shyti@kernel.org>, Mark Brown <broonie@kernel.org>, Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>, Alim Akhtar <alim.akhtar@samsung.com>, linux-spi@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] spi: s3c64xx: Use DMA mode from fifo size Date: Thu, 28 Mar 2024 12:58:07 -0500 [thread overview] Message-ID: <CAPLW+4k4qh4ZYBufZoGbUZN0yxSE2X8bOdkEQVw1Zg9YUVpbug@mail.gmail.com> (raw) In-Reply-To: <20240327033041.83625-1-jaewon02.kim@samsung.com> On Tue, Mar 26, 2024 at 10:35 PM Jaewon Kim <jaewon02.kim@samsung.com> wrote: > > The SPI data size is smaller than FIFO, it operates in PIO mode, Spelling: "The" -> "If the" > and if it is larger than FIFO mode, DMA mode is selected. > > If the data size is the same as the FIFO size, it operates in PIO mode > and data is separated into two transfer. In order to prevent, Nit: "transfer" -> "transfers", "prevent" -> "prevent it" > DMA mode must be used from the case of FIFO and data size. > You probably mean this code (it occurs two times in the driver): xfer->len = fifo_len - 1; Can you please elaborate on why it's done this way? Why can't we just do "xfer->len = fifo_len" and use the whole FIFO for the transfer instead? I don't understand the necessity to split the transfer into two chunks if its size is of FIFO length -- wouldn't it fit into FIFO in that case? (I'm pretty sure this change is correct, just want to understand how exactly it works). > Fixes: 1ee806718d5e ("spi: s3c64xx: support interrupt based pio mode") Just wonder if that fixes some throughput regression, or something worse (like failed transfers when the transfer size is the same as FIFO size)? > Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com> > --- > drivers/spi/spi-s3c64xx.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c > index 9fcbe040cb2f..81ed5fddf83e 100644 > --- a/drivers/spi/spi-s3c64xx.c > +++ b/drivers/spi/spi-s3c64xx.c > @@ -430,7 +430,7 @@ static bool s3c64xx_spi_can_dma(struct spi_controller *host, > struct s3c64xx_spi_driver_data *sdd = spi_controller_get_devdata(host); > > if (sdd->rx_dma.ch && sdd->tx_dma.ch) > - return xfer->len > sdd->fifo_depth; > + return xfer->len >= sdd->fifo_depth; > > return false; > } > @@ -826,11 +826,11 @@ static int s3c64xx_spi_transfer_one(struct spi_controller *host, > return status; > } > > - if (!is_polling(sdd) && (xfer->len > fifo_len) && > + if (!is_polling(sdd) && xfer->len >= fifo_len && > sdd->rx_dma.ch && sdd->tx_dma.ch) { > use_dma = 1; > Would be nice to remove this empty line, while at it. > - } else if (xfer->len >= fifo_len) { > + } else if (xfer->len > fifo_len) { Below in the same function I can see similar code: if (target_len >= fifo_len) xfer->len = fifo_len - 1; Shouldn't that 'if' condition be fixed too? Or it's ok as it is? (Just noticed it by searching, not sure myself, hence asking). > tx_buf = xfer->tx_buf; > rx_buf = xfer->rx_buf; > origin_len = xfer->len; > -- > 2.43.2 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2024-03-28 17:58 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <CGME20240327033501epcas2p2bbe21301da5584f7f3a073c51a363c00@epcas2p2.samsung.com> 2024-03-27 3:30 ` [PATCH] spi: s3c64xx: Use DMA mode from fifo size Jaewon Kim 2024-03-27 3:30 ` Jaewon Kim 2024-03-28 17:58 ` Sam Protsenko [this message] 2024-03-28 17:58 ` Sam Protsenko 2024-03-29 5:53 ` Jaewon Kim 2024-03-29 5:53 ` Jaewon Kim 2024-03-29 6:01 ` Sam Protsenko 2024-03-29 6:01 ` Sam Protsenko [not found] <CGME20240329090313epcas2p2cf95d22e44b6b1c120021622da68aeb8@epcas2p2.samsung.com> 2024-03-29 8:58 ` Jaewon Kim 2024-03-29 8:58 ` Jaewon Kim 2024-03-29 9:09 ` Jaewon Kim 2024-03-29 9:09 ` Jaewon Kim 2024-03-29 17:35 ` Mark Brown 2024-03-29 17:35 ` Mark Brown
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=CAPLW+4k4qh4ZYBufZoGbUZN0yxSE2X8bOdkEQVw1Zg9YUVpbug@mail.gmail.com \ --to=semen.protsenko@linaro.org \ --cc=alim.akhtar@samsung.com \ --cc=andi.shyti@kernel.org \ --cc=broonie@kernel.org \ --cc=jaewon02.kim@samsung.com \ --cc=krzysztof.kozlowski@linaro.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-samsung-soc@vger.kernel.org \ --cc=linux-spi@vger.kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.