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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2 04/15] spi: Replace open coded spi_controller_xfer_timeout() Content-Language: en-US To: Andy Shevchenko , Mark Brown , Cristian Ciocaltea , Yang Yingliang , Amit Kumar Mahapatra via Alsa-devel , Neil Armstrong , Tharun Kumar P , Vijaya Krishna Nivarthi , =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= , linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-riscv@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, linux-trace-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: Sanjay R Mehta , Radu Pirea , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Tudor Ambarus , Serge Semin , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Matthias Brugger , Andy Gross , Bjorn Andersson , Konrad Dybcio , Heiko Stuebner , Palmer Dabbelt , Paul Walmsley , Orson Zhai , Baolin Wang , Chunyan Zhang , Alain Volmat , Maxime Coquelin , Alexandre Torgue , Max Filippov , Steven Rostedt , Masami Hiramatsu , Richard Cochran References: <20230710154932.68377-1-andriy.shevchenko@linux.intel.com> <20230710154932.68377-5-andriy.shevchenko@linux.intel.com> From: AngeloGioacchino Del Regno In-Reply-To: <20230710154932.68377-5-andriy.shevchenko@linux.intel.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230711_012820_541887_62A2119D X-CRM114-Status: GOOD ( 31.16 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org Il 10/07/23 17:49, Andy Shevchenko ha scritto: > Since the new spi_controller_xfer_timeout() helper appeared, > we may replace open coded variant in spi_transfer_wait(). > > Signed-off-by: Andy Shevchenko > --- > drivers/spi/spi.c | 25 ++----------------------- > include/linux/spi/spi.h | 6 +++++- > 2 files changed, 7 insertions(+), 24 deletions(-) > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index 125dea8fae00..c99ee4164f11 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -1342,8 +1342,7 @@ static int spi_transfer_wait(struct spi_controller *ctlr, > { > struct spi_statistics __percpu *statm = ctlr->pcpu_statistics; > struct spi_statistics __percpu *stats = msg->spi->pcpu_statistics; > - u32 speed_hz = xfer->speed_hz; > - unsigned long long ms; > + unsigned long ms; > > if (spi_controller_is_slave(ctlr)) { > if (wait_for_completion_interruptible(&ctlr->xfer_completion)) { > @@ -1351,29 +1350,9 @@ static int spi_transfer_wait(struct spi_controller *ctlr, > return -EINTR; > } > } else { > - if (!speed_hz) > - speed_hz = 100000; > - > - /* > - * For each byte we wait for 8 cycles of the SPI clock. > - * Since speed is defined in Hz and we want milliseconds, > - * use respective multiplier, but before the division, > - * otherwise we may get 0 for short transfers. > - */ > - ms = 8LL * MSEC_PER_SEC * xfer->len; > - do_div(ms, speed_hz); > - > - /* > - * Increase it twice and add 200 ms tolerance, use > - * predefined maximum in case of overflow. > - */ > - ms += ms + 200; > - if (ms > UINT_MAX) > - ms = UINT_MAX; > - > + ms = spi_controller_xfer_timeout(ctlr, xfer); I agree on using helpers, but the logic is slightly changing here: yes it is unlikely (and also probably useless) to get ms == UINT_MAX, but the helper is limiting the maximum timeout value to 500mS, which may not work for some slow controllers/devices. This should get validated on more than a few platforms, and I'm not sure that this kind of validation would be "fast" to get... so, probably the best thing to do here is to add a warning in case the timeout exceeds 500mS, print the actual value, keep it like this for a kernel version or two and check reports: that would allow to understand what a safe maximum timeout value could be. Aside from that, I wouldn't drop those nice comments explaining how/why the timeout is calculated: I know how, but not everyone knows in advance. Regards, Angelo > ms = wait_for_completion_timeout(&ctlr->xfer_completion, > msecs_to_jiffies(ms)); > - > if (ms == 0) { > SPI_STATISTICS_INCREMENT_FIELD(statm, timedout); > SPI_STATISTICS_INCREMENT_FIELD(stats, timedout); > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index 32c94eae8926..0ce1cb18a076 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -1270,12 +1270,16 @@ static inline bool spi_is_bpw_supported(struct spi_device *spi, u32 bpw) > * that it would take on a single data line and take twice this amount of time > * with a minimum of 500ms to avoid false positives on loaded systems. > * > + * Assume speed to be 100 kHz if it's not defined at the time of invocation. > + * > * Returns: Transfer timeout value in milliseconds. > */ > static inline unsigned int spi_controller_xfer_timeout(struct spi_controller *ctlr, > struct spi_transfer *xfer) > { > - return max(xfer->len * 8 * 2 / (xfer->speed_hz / 1000), 500U); > + u32 speed_hz = xfer->speed_hz ?: 100000; > + > + return max(xfer->len * 8 * 2 / (speed_hz / 1000), 500U); > } > > /*---------------------------------------------------------------------------*/ _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic