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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2 3/4] spi: s3c64xx: add sleep during transfer Content-Language: en-US To: Krzysztof Kozlowski , Mark Brown , Andi Shyti , Alim Akhtar Cc: linux-spi@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Chanho Park From: Jaewon Kim In-Reply-To: Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrCJsWRmVeSWpSXmKPExsWy7bCmme7h7fYpBvP+cFg8mLeNzWLxj+dM FlMfPmGzuLxf22Lv663sFpseX2O1uLxrDpvFjPP7mCwaP95kd+D0uL7kE7PHplWdbB53ru1h 89i8pN6jb8sqRo/Pm+QC2KKybTJSE1NSixRS85LzUzLz0m2VvIPjneNNzQwMdQ0tLcyVFPIS c1NtlVx8AnTdMnOAblJSKEvMKQUKBSQWFyvp29kU5ZeWpCpk5BeX2CqlFqTkFJgX6BUn5haX 5qXr5aWWWBkaGBiZAhUmZGcsvm9Z8Iy7Ytk+1QbGtZxdjJwcEgImEhc+HmfqYuTiEBLYwShx p/c/lPOJUeL8k+2MEM43Rok169+zwbR0rV7NDpHYyyjxcVoDVNVrRok3K/pYQKp4BewkOg7+ AbNZBFQlWh6vYoOIC0qcnPkELC4qEC2xeN8UMFtYwFli362l7CA2s4C4xK0n88HuEBFYzCjR 9/gTG4jDLLCRUWJz01SwKjYBbYnv6xezgticQNuWzLnGBtEtL7H97RxmkAYJgYUcEj8Oz2KB ONxF4svSPqgnhCVeHd/CDmFLSbzsb4OysyXap/9hhbArJC5umA1Vbywx61k70J8cQAs0Jdbv 0gcxJQSUJY7cYoFYyyfRcfgvO0SYV6KjTQiiUU3i/tRzUENkJCYdWckEYXtI/J81j2UCo+Is pGCZheT9WUiemYWwdwEjyypGsdSC4tz01GKjAhN4ZCfn525iBCdXLY8djLPfftA7xMjEwXiI UYKDWUmE94yrVYoQb0piZVVqUX58UWlOavEhRlNg5ExklhJNzgem97ySeEMTSwMTMzNDcyNT A3Mlcd6PHcopQgLpiSWp2ampBalFMH1MHJxSDUz7b69pXvGe/dPh07n9sjpXPyZvkfBtLiq5 k7bAOuvmqvDTQTZxdeKT3W2jtT4ErV69OFwwxZh9veUWOYZ4jYvfGT203Xef+uCo+uuFx0+1 hymKDbLdPc/72Mvvvf/K/rvuGS+vzRkdbsfc8zEz7+gsFw5xtQp9Jn6hxW7+M8Zd7488+jdN dY1J/NXlTu09XS2PQmJ38Dmnx4UUvQsu1H/4eeJq+2+cfKdiUp9sOyau+LXtcm67yk3ndU/Z 5nRF6fgFbpZd7Mia3N+4Ifqr+nmXguJLrifLvZbNDeHXrPu2afXdus3su2s33YgIn8JjyyzT J7ZzhW73hWM+Qn7L1nM/NBW3q1ZYvcuz2/5dvRJLcUaioRZzUXEiAOqLIiA3BAAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmplkeLIzCtJLcpLzFFi42LZdlhJTvfQdvsUg7efFSwezNvGZrH4x3Mm i6kPn7BZXN6vbbH39VZ2i02Pr7FaXN41h81ixvl9TBaNH2+yO3B6XF/yidlj06pONo871/aw eWxeUu/Rt2UVo8fnTXIBbFFcNimpOZllqUX6dglcGYvvWxY8465Ytk+1gXEtZxcjJ4eEgIlE 1+rV7F2MXBxCArsZJfr6H7JAJGQklj/rY4OwhSXutxxhhSh6ySgx4+YlZpAEr4CdRMfBP2AN LAKqEi2PV7FBxAUlTs58AhYXFYiWuLH8GxOILSzgLLHv1lJ2EJtZQFzi1pP5TCBDRQQWM0p0 XHoLdgazwEZGiZXX1zNDrPvJKPH5xGWwUWwC2hLf1y9mBbE5gVYvmXONDWKUmUTX1i5GCFte YvvbOcwTGIVmIblkFpKNs5C0zELSsoCRZRWjZGpBcW56brFhgWFearlecWJucWleul5yfu4m RnBMaWnuYNy+6oPeIUYmDsZDjBIczEoivGdcrVKEeFMSK6tSi/Lji0pzUosPMUpzsCiJ817o OhkvJJCeWJKanZpakFoEk2Xi4JRqYDp9+OdF4aXv6jYa9KU+jgowYYtZYV68WCsx4tn3BJFD TX9iTXVcPWXPTa32ufTqofL/cmH/vXv8Hu695Hl81wrflM1PghyDs/Z8nrNzb9492+Urcx9I LXM7HrmrrPOIyoysHWGha5pfnAwU28e5vKV4a+OVSzMCs4+8lK53tDTqlDupusWoMd6PXTBY VrFPjHmS2h75rjtvnvm/Klrevz1PcmKBuNFxqRt9PuqztRbK1Kv3xm4/ve38+3VyQjVc+xfd l1tdJH6yf+XRDtZHF5v2aSWF/Uh52fm97Fn3vE/1PwOMLV7+cfENObGs/eaJU5WJ31SrjpSn u5+oq42bMu8i5xLOuo6d8Q5rs3dnyCuxFGckGmoxFxUnAgDT3qPwGAMAAA== X-CMS-MailID: 20230419094330epcas2p495358693c341dc79d18d7d392c435207 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20230419062755epcas2p1bca14bbd5200ebe5241780d2d7ec1596 References: <20230419060639.38853-1-jaewon02.kim@samsung.com> <20230419060639.38853-4-jaewon02.kim@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23. 4. 19. 17:19, Krzysztof Kozlowski wrote: > On 19/04/2023 08:06, Jaewon Kim wrote: >> In polling mode, the status register is constantly read to check transfer >> completion. It cause excessive CPU usage. >> So, it calculates the SPI transfer time and made it sleep. >> >> Signed-off-by: Jaewon Kim >> --- >> drivers/spi/spi-s3c64xx.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c >> index 886722fb40ea..cf3060b2639b 100644 >> --- a/drivers/spi/spi-s3c64xx.c >> +++ b/drivers/spi/spi-s3c64xx.c >> @@ -561,6 +561,14 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd, >> u32 cpy_len; >> u8 *buf; >> int ms; >> + u32 tx_time; >> + >> + /* sleep during signal transfer time */ >> + status = readl(regs + S3C64XX_SPI_STATUS); >> + if (RX_FIFO_LVL(status, sdd) < xfer->len) { >> + tx_time = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed; >> + usleep_range(tx_time / 2, tx_time); >> + } > Did you actually check the delays introduced by it? Is it worth? Yes, I already test it. Throughput was the same, CPU utilization decreased to 30~40% from 100%. Tested board is ExynosAutov9 SADK. > >> >> /* millisecs to xfer 'len' bytes @ 'cur_speed' */ >> ms = xfer->len * 8 * 1000 / sdd->cur_speed; > You have now some code duplication so this could be combined. > > Best regards, > Krzysztof > > Thanks Jaewon Kim