linux-kernel - [PATCH v6 01/16] spi: dw: Set xfer effective_speed

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Date:   Fri, 29 May 2020 16:11:50 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Mark Brown <broonie@...nel.org>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Georgy Vlasov <Georgy.Vlasov@...kalelectronics.ru>,
        Ramil Zaripov <Ramil.Zaripov@...kalelectronics.ru>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>, Feng Tang <feng.tang@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rob Herring <robh+dt@...nel.org>, <linux-mips@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v6 01/16] spi: dw: Set xfer effective_speed_hz

Seeing DW APB SSI controller doesn't support setting the exactly
requested SPI bus frequency, but only a rounded frequency determined
by means of the odd-numbered half-worded reference clock divider,
it would be good to tune the SPI core up and initialize the current
transfer effective_speed_hz. By doing so the core will be able to
execute the xfer-related delays with better accuracy.

Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc: Georgy Vlasov <Georgy.Vlasov@...kalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@...kalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Feng Tang <feng.tang@...el.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: linux-mips@...r.kernel.org
Cc: devicetree@...r.kernel.org
---
 drivers/spi/spi-dw.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index 9d6904d30104..050cb2ea0812 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -352,6 +352,7 @@ static int dw_spi_transfer_one(struct spi_controller *master,
 		spi_set_clk(dws, chip->clk_div);
 	}
 
+	transfer->effective_speed_hz = dws->max_freq / chip->clk_div;
 	dws->n_bytes = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
 
 	cr0 = dws->update_cr0(master, spi, transfer);
-- 
2.26.2